TY - JOUR A1 - Park, Jaeheung A1 - Lühr, Hermann A1 - Kervalishvili, Guram N. A1 - Rauberg, Jan A1 - Michaelis, Ingo A1 - Stolle, Claudia A1 - Kwak, Young-Sil T1 - Nighttime magnetic field fluctuations in the topside ionosphere at midlatitudes and their relation to medium-scale traveling ionospheric disturbances: The spatial structure and scale sizes JF - Journal of geophysical research : Space physics N2 - Previous studies suggested that electric and/or magnetic field fluctuations observed in the nighttime topside ionosphere at midlatitudes generally originate from quiet time nocturnal medium-scale traveling ionospheric disturbances (MSTIDs). However, decisive evidences for the connection between the two have been missing. In this study we make use of the multispacecraft observations of midlatitude magnetic fluctuations (MMFs) in the nighttime topside ionosphere by the Swarm constellation. The analysis results show that the area hosting MMFs is elongated in the NW-SE (NE-SW) direction in the Northern (Southern) Hemisphere. The elongation direction and the magnetic field polarization support that the area hosting MMFs is nearly field aligned. All these properties of MMFs suggest that they have close relationship with MSTIDs. Expectation values of root-mean-square field-aligned currents associated with MMFs are up to about 4nA/m(2). MMF coherency significantly drops for longitudinal distances of 1 degrees. KW - midlatitude nighttime magnetic fluctuation KW - nighttime MSTID KW - Swarm constellation Y1 - 2015 U6 - https://doi.org/10.1002/2015JA021315 SN - 2169-9380 SN - 2169-9402 VL - 120 IS - 8 SP - 6818 EP - 6830 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Overduin, Pier Paul A1 - Haberland, Christian A1 - Ryberg, Trond A1 - Kneier, Fabian A1 - Jacobi, Tim A1 - Grigoriev, Mikhail N. A1 - Ohrnberger, Matthias T1 - Submarine permafrost depth from ambient seismic noise JF - Geophysical research letters N2 - Permafrost inundated since the last glacial maximum is degrading, potentially releasing trapped or stabilized greenhouse gases, but few observations of the depth of ice-bonded permafrost (IBP) below the seafloor exist for most of the arctic continental shelf. We use spectral ratios of the ambient vibration seismic wavefield, together with estimated shear wave velocity from the dispersion curves of surface waves, for estimating the thickness of the sediment overlying the IBP. Peaks in spectral ratios modeled for three-layered 1-D systems correspond with varying thickness of the unfrozen sediment. Seismic receivers were deployed on the seabed around Muostakh Island in the central Laptev Sea, Siberia. We derive depths of the IBP between 3.7 and 20.7m15%, increasing with distance from the shoreline. Correspondence between expected permafrost distribution, modeled response, and observational data suggests that the method is promising for the determination of the thickness of unfrozen sediment. KW - submarine permafrost KW - ambient noise KW - Siberia KW - continental shelf Y1 - 2015 U6 - https://doi.org/10.1002/2015GL065409 SN - 0094-8276 SN - 1944-8007 VL - 42 IS - 18 SP - 7581 EP - 7588 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Cattania, Camilla T1 - Improvement of aftershock models based on Coulomb stress changes and rate-and-state dependent friction T1 - Verbesserte Nachbebenmodelle durch Berücksichtigung von Coulombspannungsänderungen und Rate-State abhängiger Reibung N2 - Earthquake clustering has proven the most useful tool to forecast changes in seismicity rates in the short and medium term (hours to months), and efforts are currently being made to extend the scope of such models to operational earthquake forecasting. The overarching goal of the research presented in this thesis is to improve physics-based earthquake forecasts, with a focus on aftershock sequences. Physical models of triggered seismicity are based on the redistribution of stresses in the crust, coupled with the rate-and-state constitutive law proposed by Dieterich to calculate changes in seismicity rate. This type of models are known as Coulomb- rate and-state (CRS) models. In spite of the success of the Coulomb hypothesis, CRS models typically performed poorly in comparison to statistical ones, and they have been underepresented in the operational forecasting context. In this thesis, I address some of these issues, and in particular these questions: (1) How can we realistically model the uncertainties and heterogeneity of the mainshock stress field? (2) What is the effect of time dependent stresses in the postseismic phase on seismicity? I focus on two case studies from different tectonic settings: the Mw 9.0 Tohoku megathrust and the Mw 6.0 Parkfield strike slip earthquake. I study aleatoric uncertainties using a Monte Carlo method. I find that the existence of multiple receiver faults is the most important source of intrinsic stress heterogeneity, and CRS models perform better when this variability is taken into account. Epistemic uncertainties inherited from the slip models also have a significant impact on the forecast, and I find that an ensemble model based on several slip distributions outperforms most individual models. I address the role of postseismic stresses due to aseismic slip on the mainshock fault (afterslip) and to the redistribution of stresses by previous aftershocks (secondary triggering). I find that modeling secondary triggering improves model performance. The effect of afterslip is less clear, and difficult to assess for near-fault aftershocks due to the large uncertainties of the afterslip models. Off-fault events, on the other hand, are less sensitive to the details of the slip distribution: I find that following the Tohoku earthquake, afterslip promotes seismicity in the Fukushima region. To evaluate the performance of the improved CRS models in a pseudo-operational context, I submitted them for independent testing to a collaborative experiment carried out by CSEP for the 2010-2012 Canterbury sequence. Preliminary results indicate that physical models generally perform well compared to statistical ones, suggesting that CRS models may have a role to play in the future of operational forecasting. To facilitate efforts in this direction, and to enable future studies of earthquake triggering by time dependent processes, I have made the code open source. In the final part of this thesis I summarize the capabilities of the program and outline technical aspects regarding performance and parallelization strategies. N2 - Die örtliche und zeitlich Häufung von Erdbeben ist geeignet, um Änderungen in Seismizitätsraten auf kurzen bis mittleren Zeitskalen (Stunden bis Monate) zu prognostizieren. Kürzlich wurden vermehrt Anstrengungen unternommen, den Umfang solcher Modelle auf Operationelle Erdbebenvorhersage auszudehnen, welche die Veröffentlichung von Erdbebenwahrscheinlichkeiten beinhaltet mit dem Ziel, die Bevölkerung besser auf mögliche Erdbeben vorzubereiten. Das vorrangige Ziel dieser Dissertation ist die Verbesserung von kurz- und mittelfristiger Erdbebenprognose basierend auf physikalischen Modellen. Ich konzentriere mich hier auf Nachbebensequenzen. Physikalische Modelle, die getriggerte Seimizität erklären, basieren auf der Umverteilung von Spannungen in der Erdkruste. Berechnung der Coulomb Spannung können kombiniert werden mit dem konstituivem Gesetz von Dieterich, welches die Berechnung von Änderungen in der Seismizitätsrate ermöglicht. Diese Modelle sind als Coulomb-Rate-and-State (CRS) Modelle bekannt. Trotz der erfolgreichen Überprüfung der Coulomb-Hypothese, schneiden CRS-Modelle im Vergleich mit statistischen Modellen schlecht ab, und wurden deshalb bisher kaum im Kontext operationeller Erdbenbenvorhersage genutzt. In dieser Arbeit, gehe ich auf einige der auftretenden Probleme ein. Im Besonderen wende ich mich den folgenden Fragen zu: (1) Wie können wir die Unsicherheiten und die Heterogenität des Spannungsfeldes infolge des Hauptbebens realistisch modellieren? (2)Welche Auswirkungen haben zeitlich variable Spannungsänderungen in der postseismischen Phase? Ich konzentriere mich hierbei auf zwei Beispiele in unterschiedlichen tektonischen Regionen: die Aufschiebung des Mw9.0 Tohoku Erdbeben und die Blattverschiebung des Mw6.0 Parkfield Erdbeben. Ich untersuche aleotorische Unsicherheiten der Coulomb-Spannung durch Variabilität in der Orientierung der betroffenen Bruchflächen und durch Spannungsgradienten innerhalb von Modellzellen. Ich zeige, dass die Existenz der unterschiedlichen Bruchflächen die bedeutenste Quelle für intrinsiche Spannungheterogenität ist und das CRS-Modelle deutlich besser abschneiden, wenn diese Variabilität berücksichtigt wird. Die epistemischen Unsicherheiten aufgrund von unterschiedlichen Ergebnissen von Inversionen von Daten für die Verschiebung entlang der Bruchfläche haben ebenso erhebliche Auswirkungen auf die Vorhersage. Ich gehe dann auf die Rolle von postseismischen Spannung ein, insbesondere auf zwei Prozesse: aseismische Verschiebung entlang der Störungsfläche des Hauptbebens (Afterslip) und die Veränderung von Spannungen durch vorhergehende Nachbeben (sekundäres Triggern). Ich demonstriere, dass das Modellieren von sekundärem Triggern die Modellvorhersage in beiden Fallbeispielen verbessert. Die Einbeziehung von Afterslip verbessert die Qualität der Vorhersage nur für die Nachbebensequenz des Parkfield Erdbebens. Dagegen kann ich nachweisen, dass Afterslip infolge des Tohoku Bebens eine höhere Seismizität auf Abschiebungsflächen im Hangenden begünstigt. Die dargestellten Verbesserungen des CRS-Modells sind sehr vielversprechend im Kontext operationeller Erdbebenvorhersage, verlangen aber nach weiterer Überprüfung. Ich stelle die vorläufigen Ergebnisse eines gemeinschaftlichen Tests für die Erdbebenfolge von Canterbury 2010-2012 vor, welcher von CSEP durchgeführt wurde. Die physikalischen Modelle schneiden hier im Vergleich mit statistischen Modellen gut ab. Daher scheint eine Anwendung von CSR-Modellen, die Unsicherheiten und sekundäres Triggering berücksichtigen, in zukünftigen operationellen Erdbebenvorhersagen empfehlenswert. Um die Bemühungen in dieser Richtung zu unterstützen und weitere Studien zum Triggern von Erdbeben durch zeitabhängige Prozesse zu ermöglichen, habe ich meinen Open Source Code öffentlich zugänglich gemacht. Im letzen Teil dieser Arbeit fasse ich die Leistungsfähigkeit des Programms zusammen und skizziere die technischen Aspekte bezüglich der Effiziens und der Parallelisierung des Programmes. KW - earthquake forecasting KW - earthquake interaction KW - Coulomb stress KW - rate-state friction KW - Erdbebenvorhersage KW - Coulombspannung KW - Erdbebenwechselwirkung Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-87097 ER - TY - THES A1 - Ramisch, Arne T1 - Lake system development on the northern Tibetan Plateau during the last ~ 12 ka Y1 - 2015 ER - TY - THES A1 - Rach, Oliver T1 - Qualitative and quantitative estimations of hydrological changes in western Europe during abrupt climate shifts using lipid biomarker derived stable hydrogen isotope records Y1 - 2015 ER - TY - THES A1 - Mielke, Christian T1 - Multi- and Hyperspectral Spaceborne Remote Sensing for Mine Waste and Mineral Deposit Characterization, new Applications to the EnMAP and Sentinel-2 Missions Y1 - 2015 ER - TY - JOUR A1 - Sunyer, M. A. A1 - Hundecha, Y. A1 - Lawrence, D. A1 - Madsen, H. A1 - Willems, Patrick A1 - Martinkova, M. A1 - Vormoor, Klaus Josef A1 - Bürger, Gerd A1 - Hanel, M. A1 - Kriauciuniene, J. A1 - Loukas, A. A1 - Osuch, M. A1 - Yucel, I. T1 - Inter-comparison of statistical downscaling methods for projection of extreme precipitation in Europe JF - Hydrology and earth system sciences : HESS N2 - Information on extreme precipitation for future climate is needed to assess the changes in the frequency and intensity of flooding. The primary source of information in climate change impact studies is climate model projections. However, due to the coarse resolution and biases of these models, they cannot be directly used in hydrological models. Hence, statistical downscaling is necessary to address climate change impacts at the catchment scale. This study compares eight statistical downscaling methods (SDMs) often used in climate change impact studies. Four methods are based on change factors (CFs), three are bias correction (BC) methods, and one is a perfect prognosis method. The eight methods are used to downscale precipitation output from 15 regional climate models (RCMs) from the ENSEMBLES project for 11 catchments in Europe. The overall results point to an increase in extreme precipitation in most catchments in both winter and summer. For individual catchments, the downscaled time series tend to agree on the direction of the change but differ in the magnitude. Differences between the SDMs vary between the catchments and depend on the season analysed. Similarly, general conclusions cannot be drawn regarding the differences between CFs and BC methods. The performance of the BC methods during the control period also depends on the catchment, but in most cases they represent an improvement compared to RCM outputs. Analysis of the variance in the ensemble of RCMs and SDMs indicates that at least 30% and up to approximately half of the total variance is derived from the SDMs. This study illustrates the large variability in the expected changes in extreme precipitation and highlights the need for considering an ensemble of both SDMs and climate models. Recommendations are provided for the selection of the most suitable SDMs to include in the analysis. Y1 - 2015 U6 - https://doi.org/10.5194/hess-19-1827-2015 SN - 1027-5606 SN - 1607-7938 VL - 19 IS - 4 SP - 1827 EP - 1847 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Heistermann, Maik A1 - Collis, Scott A1 - Dixon, M. J. A1 - Helmus, J. J. A1 - Henja, A. A1 - Michelson, D. B. A1 - Pfaff, Thomas T1 - An Open Virtual Machine for Cross-Platform Weather Radar Science JF - Bulletin of the American Meteorological Society : BAMS N2 - In a recent BAMS article, it is argued that community-based Open Source Software (OSS) could foster scientific progress in weather radar research, and make weather radar software more affordable, flexible, transparent, sustainable, and interoperable. Nevertheless, it can be challenging for potential developers and users to realize these benefits: tools are often cumbersome to install; different operating systems may have particular issues, or may not be supported at all; and many tools have steep learning curves. To overcome some of these barriers, we present an open, community-based virtual machine (VM). This VM can be run on any operating system, and guarantees reproducibility of results across platforms. It contains a suite of independent OSS weather radar tools (BALTRAD, Py-ART, wradlib, RSL, and Radx), and a scientific Python stack. Furthermore, it features a suite of recipes that work out of the box and provide guidance on how to use the different OSS tools alone and together. The code to build the VM from source is hosted on GitHub, which allows the VM to grow with its community. We argue that the VM presents another step toward Open (Weather Radar) Science. It can be used as a quick way to get started, for teaching, or for benchmarking and combining different tools. It can foster the idea of reproducible research in scientific publishing. Being scalable and extendable, it might even allow for real-time data processing. We expect the VM to catalyze progress toward interoperability, and to lower the barrier for new users and developers, thus extending the weather radar community and user base. Y1 - 2015 U6 - https://doi.org/10.1175/BAMS-D-14-00220.1 SN - 0003-0007 SN - 1520-0477 VL - 96 SP - 1641 EP - 1645 PB - American Meteorological Society CY - Boston ER - TY - THES A1 - Aygül, Mesut T1 - Pre-collisional accretion and exhumation along the southern Laurasian active margin, Central Pontides, Turkey T1 - Prä-Kollisions Akkretion und Exhumierung entlang des aktiven südlichen Kontinentalrands Laurassisens, mittlere Pontiden, Türkei N2 - The Central Pontides is an accretionary-type orogenic area within the Alpine-Himalayan orogenic belt characterized by pre-collisional tectonic continental growth. The region comprises Mesozoic subduction-accretionary complexes and an accreted intra-oceanic arc that are sandwiched between the Laurasian active continental margin and Gondwana-derived the Kırşehir Block. The subduction-accretion complexes mainly consist of an Albian-Turonian accretionary wedge representing the Laurasian active continental margin. To the north, the wedge consists of slate/phyllite and metasandstone intercalation with recrystallized limestone, Na-amphibole-bearing metabasite (PT= 7–12 kbar and 400 ± 70 ºC) and tectonic slices of serpentinite representing accreted distal part of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed. Raman spectra of carbonaceous material (RSCM) of the metapelitic rocks revealed that the metaflysch sequence consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330 °C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. The rest are phyllites that are characterized by slightly pronounced G band with D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 °C. The phyllites are associated with a strip of incipient blueschist facies metabasites which are found as slivers within the offscraped distal turbidites. They possibly represent underplated continental metasediments together with oceanic crustal basalt along the basal décollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge. 40Ar/39Ar phengite ages from the phyllites are ca. 100 Ma, indicating Albian subduction and regional HP metamorphism. The accreted continental metasediments are underlain by HP/LT metamorphic rocks of oceanic origin along an extensional shear zone. The oceanic metamorphic sequence mainly comprises tectonically thickened deep-seated eclogite to blueschist facies metabasites and micaschists. In the studied area, metabasites are epidote-blueschists locally with garnet (PT= 17 ± 1 kbar and 500 ± 40 °C). Lawsonite-blueschists are exposed as blocks along the extensional shear zone (PT= 14 ± 2 kbar and 370–440 °C). They are possibly associated with low shear stress regime of the initial stage of convergence. Close to the shear zone, the footwall micaschists consist of quartz, phengite, paragonite, chlorite, rutile with syn-kinematic albite porphyroblast formed by pervasive shearing during exhumation. These types of micaschists are tourmaline-bearing and their retrograde nature suggests high-fluid flux along shear zones. Peak metamorphic mineral assemblages are partly preserved in the chloritoid-micaschist farther away from the shear zone representing the zero strain domains during exhumation. Three peak metamorphic assemblages are identified and their PT conditions are constrained by pseudosections produced by Theriak-Domino and by Raman spectra of carbonaceous material: 1) garnet-chloritoid-glaucophane with lawsonite pseudomorphs (P= 17.5 ± 1 kbar, T: 390-450 °C) 2) chloritoid with glaucophane pseudomorphs (P= 16-18 kbar, T: 475 ± 40 °C) and 3) relatively high-Mg chloritoid (17%) with jadeite pseudomorphs (P= 22-25 kbar; T: 440 ± 30 °C) in addition to phengite, paragonite, quartz, chlorite, rutile and apatite. The last mineral assemblage is interpreted as transformation of the chloritoid + glaucophane assemblage to chloritoid + jadeite paragenesis with increasing pressure. Absence of tourmaline suggests that the chloritoid-micaschist did not interact with B-rich fluids during zero strain exhumation. 40Ar/39Ar phengite age of a pervasively sheared footwall micaschist is constrained to 100.6 ± 1.3 Ma and that of a chloritoid-micaschist is constrained to 91.8 ± 1.8 Ma suggesting exhumation during on-going subduction with a southward younging of the basal accretion and the regional metamorphism. To the south, accretionary wedge consists of blueschist and greenschist facies metabasite, marble and volcanogenic metasediment intercalation. 40Ar/39Ar phengite dating reveals that this part of the wedge is of Middle Jurassic age partly overprinted during the Albian. Emplacement of the Middle Jurassic subduction-accretion complexes is possibly associated with obliquity of the Albian convergence. Peak metamorphic assemblages and PT estimates of the deep-seated oceanic metamorphic sequence suggest tectonic stacking within wedge with different depths of burial. Coupling and exhumation of the distinct metamorphic slices are controlled by decompression of the wedge possibly along a retreating slab. Structurally, decompression of the wedge is evident by an extensional shear zone and the footwall micaschists with syn-kinematic albite porphyroblasts. Post-kinematic garnets with increasing grossular content and pseudomorphing minerals within the chloritoid-micaschists also support decompression model without an extra heating. Thickening of subduction-accretionary complexes is attributed to i) significant amount of clastic sediment supply from the overriding continental domain and ii) deep level basal underplating by propagation of the décollement along a retreating slab. Underplating by basal décollement propagation and subsequent exhumation of the deep-seated subduction-accretion complexes are connected and controlled by slab rollback creating a necessary space for progressive basal accretion along the plate interface and extension of the wedge above for exhumation of the tectonically thickened metamorphic sequences. This might be the most common mechanism of the tectonic thickening and subsequent exhumation of deep-seated HP/LT subduction-accretion complexes. To the south, the Albian-Turonian accretionary wedge structurally overlies a low-grade volcanic arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed north of the İzmir-Ankara-Erzincan suture (İAES), separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metavolcanic rocks are stratigraphically overlain by recrystallized micritic limestone with rare volcanogenic metaclastic rocks. Two groups can be identified based on trace and rare earth element characteristics. The first group consists of basaltic andesite/andesite (BA1) and rhyolite with abundant cognate gabbroic xenoliths. It is characterized by relative enrichment of LREE with respect to HREE. The rocks are enriched in fluid mobile LILE, and strongly depleted in Ti and P reflecting fractionation of Fe-Ti oxides and apatite, which are found in the mafic cognate xenoliths. Abundant cognate gabbroic xenoliths and identical trace and rare earth elements compositions suggest that rhyolites and basaltic andesites/andesites (BA1) are cogenetic and felsic rocks were derived from a common mafic parental magma by fractional crystallization and accumulation processes. The second group consists only of basaltic andesites (BA2) with flat REE pattern resembling island arc tholeiites. Although enriched in LILE, this group is not depleted in Ti or P. Geochemistry of the metavolcanic rocks indicates supra-subduction volcanism evidenced by depletion of HFSE and enrichment of LILE. The arc sequence is sandwiched between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic mélange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kösdağ Arc was intra-oceanic. This is in accordance with basaltic andesites (BA2) with island arc tholeiite REE pattern. Zircons from two metarhyolite samples give Late Cretaceous (93.8 ± 1.9 and 94.4 ± 1.9 Ma) U/Pb ages. Low-grade regional metamorphism of the intra-oceanic arc sequence is constrained 69.9 ± 0.4 Ma by 40Ar/39Ar dating on metamorphic muscovite from a metarhyolite indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. The youngest 40Ar/39Ar phengite age from the overlying subduction-accretion complexes is 92 Ma confirming southward younging of an accretionary-type orogenic belt. Hence, the arc sequence represents an intra-oceanic paleo-arc that formed above the sinking Tethyan slab and finally accreted to Laurasian active continental margin. Abrupt non-collisional termination of arc volcanism was possibly associated with southward migration of the arc volcanism similar to the Izu-Bonin-Mariana arc system. The intra-oceanic Kösdağ Arc is coeval with the obducted supra-subduction ophiolites in NW Turkey suggesting that it represents part of the presumed but missing incipient intra-oceanic arc associated with the generation of the regional supra-subduction ophiolites. Remnants of a Late Cretaceous intra-oceanic paleo-arc and supra-subduction ophiolites can be traced eastward within the Alp-Himalayan orogenic belt. This reveals that Late Cretaceous intra-oceanic subduction occurred as connected event above the sinking Tethyan slab. It resulted as arc accretion to Laurasian active margin and supra-subduction ophiolite obduction on Gondwana-derived terranes. N2 - Die Mittelpontiden sind ein akkretionäres orogenes Gebiet innerhalb des Alpen-Himalaya Orogengürtels, das durch präkollisionales tektonisches kontinentales Wachstum gekennzeichnet ist. Die Region umfasst mesozoische subduktions-akkretions Komplexe und einen akkretierten intraozeanischen Bogen, die zwischen dem aktiven laurassischen Kontinentalrand und dem von Gondwana abgeleiteten Kırşehir Block eingeklemmt sind. Die Subduktions-Akkretionskomplexe bestehen hauptsächlich aus einem Alb-Turon Akkretionskeil, der den aktiven laurassischen Kontinentalrand repräsentiert. Im Norden besteht der Keil aus Schiefer/Phyllit und Metasandsteineinlagerungen mit rekristallisiertem Kalkstein, Na-Amphibole-tragendem Metabasit (PT= 7-12 kbar und 400 ± 70 ºC) und tektonischen Serpentinit-Einlagerungen, die einen distalen Teil eines großen submarinen Turbiditfächers der Unterkreide darstellen, der auf dem aktiven Kontinentalrand von Lauras abgelagert und anschließend akkretiert und metamorphisiert wurde. Ramanspektren von kohlenstoffhaltigem Material (RSCM) der metapelitischen Gesteine zeigen, dass die Metaflyschsequenz aus metamorphen Paketen mit ausgeprägten metamorphen Temperaturspitzen besteht. Die Mehrheit der Metapelite sind Niedertemperatur (ca. 330 °C) Schiefer, die sich durch eine mangelnde Differenzierung der Defektbänder Graphit (G) und D2 auszeichnen. Sie stellen möglicherweise abgetragene distale Turbidite entlang der Sohle des Akkretionskeils im Alb dar. Der Rest sind Phyllite, die sich durch ein leicht ausgeprägtes G-Band mit D2-Defektband an der Schulter auszeichnen. Die metamorphen Temperaturen dieser Phyllite sind auf 370-385 °C begrenzt. Die Phyllite sind mit Streifen von Metabasiten der beginnenden blauen Fazies assoziiert, die sich als Bänder innerhalb der abgetragenen distalen Turbidite befinden. Sie stellen möglicherweise unterschichtete kontinentale Metasedimente zusammen mit ozeanischem Krustenbasalt entlang des basalen Decollements dar. Die tektonische Einlagerung der unterschobenen Gesteine in die abgetragenen distalen Turbidite wurde möglicherweise durch "out-of-sequence thrusting" erreicht, was zu einer tektonischen Verdickung und Hebung des Keils führte. 40Ar/39Ar Phengit Alter von den Phylliten sind ca. 100 Ma, was auf Subduktion und regionale HP-Metamorphose während dem Alb hinweist. Die akkretierten kontinentalen Metasedimente werden von HP/LT-metamorphen Gesteinen ozeanischen Ursprungs entlang einer ausgedehnten Scherzone durchzogen. Die ozeanisch metamorphe Sequenz umfasst hauptsächlich tektonisch verdickte, tief sitzende Eklogite bis hin zu blauschieferfaziellen Metabasiten und Glimmerschiefern. Im Untersuchungsgebiet treten Metabasite als Epidot-Blauschiefer lokal mit Granat auf (PT= 17 ± 1 kbar und 500 ± 40 °C). Lawsonit-Blauschiefer treten als Blöcke entlang einer Extensionsscherzone auf (PT= 14 ± 2 kbar und 370-440 °C). Sie sind möglicherweise mit einem niedrigen Scherspannungsregime während der Anfangsphase der Konvergenz verbunden. In der Nähe der Scherzone bestehen die Glimmerschiefer aus Quarz, Phengit, Paragonit, Chlorit, Rutil und syn-kinematischen Albitporphyroblasten, die durch Scherung während der Exhumierung entstanden. Die Glimmerschiefer führen Turmalin und ihre retrograde Natur deutet auf hohen Fluidflux entlang der Scherzonen. Mineralvergesellschaftungen des metamorphen Maximums sind, weiter weg von der Scherzone, teilweise noch in den Chloritoid-Glimmerschiefern erhalten. Diese Domänen erfuhren während der Exhumierung keinen Strain. Drei metamorphe Vergesellschaftungen wurden identifiziert und ihre PT-Bedingungen durch Theriak-Domino Modellierung und Raman-Spektren von kohlenstoffhaltigem Material eingeschränkt: 1) Granat-Chloritoid-Glaukophan mit Lawsonit-Pseudomorphen (P= 17.5 ± 1 kbar, T: 390-450 °C); 2) Chloritoid mit Glaukophan-Pseudomorphen (P= 16-18 kbar, T: 475 ± 40 °C) und 3) relativ hoch-Mg-Chloritoid (17%) mit Jadeit-Pseudomorphen (P= 22-25 kbar; T: 440 ± 30 °C) zusätzlich zu Phengit, Paragonit, Quarz, Chlorit, Rutil und Apatit. Die letzte Mineralparagenese wird interpretiert als Transformation der Chloritoid + Glaukophan Vergesellschaftung zu Chloritoid + Jadeit Paragenese mit steigendem Druck. Das Fehlen von Turmalin deutet darauf hin, dass der Chloritoid-Glimmerschiefer während der strain-freien Exhumierung nicht mit B-reichen Fluiden reagiert hat. Das 40Ar/39Ar Phengitalter eines penetrativ geschieferten Glimmerschiefers ist auf 100,6 ± 1,3 Ma und das eines Chlorit-Glimmerschiefers auf 91,8 ± 1,8 Ma begrenzt, was auf eine Exhumierung während der laufenden Subduktion mit einer südlichen Verjüngung der Basalakkretion und des regionalen Metamorphismus hindeutet. Im Süden besteht der Akkretionskeil aus blauschiefer- und grünschieferfaziellen Metabasiten, Marmoren und vulkanogenen Metasedimenteinlagerungen. 40Ar/39Ar Phengit Datierung zeigt, dass dieser Teil des Keils aus dem Mittleren Jura stammt, der während des Albs teilweise überprägt wurde. Die Platznahe der Subduktions-/Akkretionskomplexe des Mittleren Jura ist möglicherweise mit einer schiefen Lage der Konvergenz im Alb verbunden. Peak metamorphe Mineralvergesellschaftungen und PT-Schätzungen der tiefliegenden ozeanischen metamorphen Sequenz deuten auf eine tektonische Stapelung im Akkretionskeil mit unterschiedlichen Grabentiefen hin. Die Kopplung und Exhumierung der einzelnen metamorphen Einheiten wird durch Dekompression des Keils gesteuert, möglicherweise entlang einer sich zurückziehenden Platte. Strukturell ist die Dekompression des Keils durch eine ausgedehnte Scherzone und die Glimmerschiefer der Basis mit syn-kinematischen Albitporphyroblasten erkennbar. Postkinematische Granate mit steigendem Grossulargehalt und pseudomorphe Mineralien innerhalb der Chloritoid-Glimmerschiefer unterstützen ein Dekompressionsmodell ohne zusätzliche Erwärmung. Die Verdickung der Subduktions-/Akkretionskomplexe wird zugeschrieben: i) einer signifikanten Menge an klastischer Sedimentzufuhr aus dem überschobenen kontinentalen Bereich und ii) tiefer basaler Unterschiebung durch Ausbreitung des Decollements entlang einer sich zurückziehenden Platte. Die Unterschiebung durch basale Decollementausbreitung und anschließende Exhumierung der tief liegenden Subduktions-Akkretionskomplexe wird durch Slab-Rollback gesteuert. Dadurch wird der notwendige Raum für eine progressive basale Akkretion entlang der Plattengrenze und der Verlängerung des überliegenden Keils für die Exhumierung der tektonisch verdickten metamorphen Sequenzen geschaffen. Dies könnte der wichtigste Mechanismus tektonischer Verdickung und anschließender Exhumierung von tief sitzenden HP/LT-Subduktions-Akkretionskomplexen sein. Im Süden liegt der Akkretionskeil des Alb-Turon strukturell über einer vulkanischen Bogensequenz aus niedriggradigen metavulkanischem Gestein und darüber liegender metasedimentärer Abfolge. Diese Metavulkanite, treten nördlich der İzmir-Ankara-Erzincan Sutur (İAES), welche Laurasia von der aus Gondwana stammenden Terranen trennt. Die metavulkanischen Gesteine bestehen hauptsächlich aus basaltischem Andesit/Andesit und Rhyolith mit mafischen Xenolithen sowie mit ihren pyroklastischen Äquivalenten, welche mit rekristallisiertem pelagischem Kalkstein und Hornstein durchsetzt sind. Die metavulkanischen Gesteine sind stratigraphisch überlagert von rekristallisiertem mikritischem Kalkstein mit seltenen vulkanischen metaklastischen Gesteinen. Zwei Gruppen können anhand von Spuren- und Seltenerden-gehalten identifiziert werden. Die erste Gruppe besteht aus basaltischem Andesit/Andesit (BA1) und Rhyolith mit zahlreichen gabbroiden Xenolithen. Sie ist durch eine relative Anreicherung von LREE gegenüber HREE gekennzeichnet. Die Gesteine sind mit fluidmobilen LILE angereichert und stark in Ti und P abgereichert, was die Fraktionierung von Fe-Ti-Oxiden und Apatit widerspiegelt, die in den mafischen Xenolithen zu finden sind. Reichlich gabbroide Xenolithe und identische Spuren- und Seltenerdelemente-Zusammensetzungen deuten darauf hin, dass Rhyolithe und basaltische Andesite/Andesite (BA1) kogenetisch sind und die felsischen Gesteine von einem gemeinsamen mafischen Magma durch fraktionierte Kristallisations- und Akkumulationsprozesse abgeleitet wurden. Die zweite Gruppe besteht nur aus basaltischen Andesiten (BA2) mit flachem REE-Muster, das an Inselbogen-Tholeiite erinnert. Obwohl angereichert mit LILE, ist diese Gruppe nicht Ti oder P verarmt. Die Geochemie der metavulkanischen Gesteine deutet auf Supra-Subduktionsvulkanismus hin, der durch den Abbau von HFSE und die Anreicherung von LILE belegt ist. Die Insel-Bogensequenz ist zwischen einem subduktions-akkretionären Komplex des Alb-Turon, der den laurassischen aktiven Kontinentalrandrand repräsentiert, und einer ophiolitischen Mélange eingeklemmt. Das Fehlen von kontinentalem Detritus in der Insel-Bogensequenz und seine tektonische Anordnung in einem breiten kreidezeitlichen Akkretionskomplex deuten darauf hin, dass der Kösdağ Arc intraozeanisch war. Dem entsprechen die basaltischen Andesiten (BA2) mit Inselbogen-Tholeiit-REE-Muster. Zirkon aus zwei Metarhyolithproben ergibt U/Pb-Alter der Spätkreide (93,8 ± 1,9 und 94,4 ± 1,9 Ma). Die niedriggradige regionale Metamorphose der intraozeanischen Bogensequenz ist durch 40Ar/39Ar Datierung von metamorphem Muskovit aus einem Metarhyolith auf 69,9 ± 0,4 Ma eingegrenzt, was darauf hindeutet, dass die Insel-Bogensequenz in der späten Kreide Teil des breiten Akkretionskomplexes der Tethys wurde. Das jüngste Phengitalter von 40Ar/39Ar aus den darüber liegenden Subduktions-Akkretionskomplexen ist 92 Ma, was die Verjüngung des akkretionären orogenen Gürtels gegen Süden bestätigt. Die Insel-Bogensequenz stellt somit einen intraozeanischen Paläobogen dar, der sich über der absinkenden Tethys-platte gebildet und schließlich an den aktiven laurassischen Kontinentalrand akkretiert hat. Der abrupte, nicht kollisionsbedingte Abbruch des Insel-Bogenvulkanismus war möglicherweise mit der südwärts Wanderung des Vulkanismus ähnlich dem Izu-Bonin-Mariana-Bogensystem verbunden. Der intraozeanische Kösdağ Bogen ist gleichaltrig zu den obduzierten Supra-Subduktionsophiolithen der Nordwesttürkei, was darauf hindeutet, dass er einen Teil des vermuteten, aber fehlenden beginnenden intraozeanischen Systems darstellt, das mit der Erzeugung der regionalen Supra-Subduktionsophiolithe verbunden ist. Überreste eines intraozeanischen Paläobogens und supra-subduzierter Ophiolithe der späten Kreide können innerhalb des orogenen Alpen-Himalaya-Gürtels nach Osten verfolgt werden. Dies zeigt, dass die intraozeanische Subduktion der Spätkreide als verbreitetes Ereignis über der absinkenden Platte der Tethys stattfand. Dieses führte zur Insel-Bogenakkretion am aktiven Kontinenntalrand Laurasirns und zur Supra-Subduktion Ophiolith-obduktion auf aus Gondwana stammenden Terranen. KW - Eurasian active margin KW - subduction-accretionary complexes KW - HP/LT metamorphism KW - Pontides KW - Eurasischer aktiver Kontinentalrand KW - subduktions-akkretions Komplexe KW - HP/LT-Metamorphose KW - Pontiden Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-416769 ER - TY - THES A1 - Priegnitz, Mike T1 - Development of geophysical methods to characterize methane hydrate reservoirs on a laboratory scale T1 - Entwicklung geophysikalischer Methoden zur Charakterisierung von Methanhydrat-Reservoiren im Labormaßstab N2 - Gashydrate sind kristalline Feststoffe bestehend aus Wasser und Gasmolekülen. Sie sind stabil bei erhöhten Drücken und niedrigen Temperaturen. Natürliche Hydratvorkommen treten daher an Kontinentalhängen, in Permafrostböden und in tiefen Seen sowie Binnenmeeren auf. Bei der Hydratbildung orientieren sich die Wassermoleküle neu und bilden sogenannte Käfigstrukturen, in die Gas eingelagert werden kann. Aufgrund des hohen Drucks bei der Hydratbildung können große Mengen an Gas in die Hydratstruktur eingebaut werden. Das Volumenverhältnis von Wasser zu Gas kann dabei bis zu 1:172 bei 0°C und Atmosphärendruck betragen. Natürliche Gashydrate enthalten hauptsächlich Methan. Da Methan sowohl ein Treibhausgas als auch ein Brenngas ist, stellen Gashydrate gleichermaßen eine potentielle Energieressource sowie eine mögliche Quelle für Treibhausgase dar. Diese Arbeit untersucht die physikalischen Eigenschaften von Methanhydrat gesättigten Sedimentproben im Labormaßstab. Dazu wurde ein großer Reservoirsimulator (LARS) mit einer eigens entwickelten elektrischen Widerstandstomographie ausgerüstet, die das erste Mal an hydratgesättigten Sedimentproben unter kontrollierten Temperatur-, Druck-, und Hydratsättigungsbedingungen im Labormaßstab angewendet wurde. Üblicherweise ist der Porenraum von (marinen) Sedimenten mit elektrisch gut leitendem Salzwasser gefüllt. Da Hydrate einen elektrischen Isolator darstellen, ergeben sich große Kontraste hinsichtlich der elektrischen Eigenschaften im Porenraum während der Hydratbildung und -zersetzung. Durch wiederholte Messungen während der Hydraterzeugung ist es möglich die räumliche Widerstandsverteilung in LARS aufzuzeichnen. Diese Daten bilden in der Folge die Grundlage für eine neue Auswerteroutine, welche die räumliche Widerstandsverteilung in die räumliche Verteilung der Hydratsättigung überführt. Dadurch ist es möglich, die sich ändernde Hydratsättigung sowohl räumlich als auch zeitlich hoch aufgelöst während der gesamten Hydraterzeugungsphase zu verfolgen. Diese Arbeit zeigt, dass die entwickelte Widerstandstomographie eine gute Datenqualität aufwies und selbst geringe Hydratsättigungen innerhalb der Sedimentprobe detektiert werden konnten. Bei der Umrechnung der Widerstandsverteilung in lokale Hydrat-Sättigungswerte wurden die besten Ergebnisse mit dem Archie-var-phi Ansatz erzielt, der die zunehmende Hydratphase dem Sedimentgerüst zuschreibt, was einer Abnahme der Porosität gleichkommt. Die Widerstandsmessungen zeigten weiterhin, dass die schnelle Hydraterzeugung im Labor zur Ausbildung von kleinen Hydratkristallen führte, die dazu neigten, zu rekristalliesieren. Es wurden weiterhin Hydrat-Abbauversuche durchgeführt, bei denen die Hydratphase über Druckerniedrigung in Anlehnung an den 2007/2008 Mallik Feldtest zersetzt wurde. Dabei konnte beobachtet werden, dass die Muster der Gas- undWasserflussraten im Labor zum Teil gut nachgebildet werden konnten, jedoch auch aufbaubedingte Abweichungen auftraten. In zwei weiteren Langzeitversuchen wurde die Realisierbarkeit und das Verhalten bei CO2-CH4-Hydrat Austauschversuchen in LARS untersucht. Das tomographische Messsystem wurde dabei genutzt um während der CH4 Hydrat Aufbauphase die Hydratverteilung innerhalb der Sedimentprobe zu überwachen. Im Zuge der anschließenden CO2-Injektion konnte mithilfe der Widerstandstomographie die sich ausbreitende CO2-Front überwacht und der Zeitpunkt des CO2 Durchbruchs identifiziert werden. N2 - Gas hydrates are crystalline solids composed of water and gas molecules. They are stable at elevated pressure and low temperatures. Therefore, natural gas hydrate deposits occur at continental margins, permafrost areas, deep lakes, and deep inland seas. During hydrate formation, the water molecules rearrange to form cavities which host gas molecules. Due to the high pressure during hydrate formation, significant amounts of gas can be stored in hydrate structures. The water-gas ratio hereby can reach up to 1:172 at 0°C and atmospheric pressure. Natural gas hydrates predominantly contain methane. Because methane constitutes both a fuel and a greenhouse gas, gas hydrates are a potential energy resource as well as a potential source for greenhouse gas. This study investigates the physical properties of methane hydrate bearing sediments on a laboratory scale. To do so, an electrical resistivity tomography (ERT) array was developed and mounted in a large reservoir simulator (LARS). For the first time, the ERT array was applied to hydrate saturated sediment samples under controlled temperature, pressure, and hydrate saturation conditions on a laboratory scale. Typically, the pore space of (marine) sediments is filled with electrically well conductive brine. Because hydrates constitute an electrical isolator, significant contrasts regarding the electrical properties of the pore space emerge during hydrate formation and dissociation. Frequent measurements during hydrate formation experiments permit the recordings of the spatial resistivity distribution inside LARS. Those data sets are used as input for a new data processing routine which transfers the spatial resistivity distribution into the spatial distribution of hydrate saturation. Thus, the changes of local hydrate saturation can be monitored with respect to space and time. This study shows that the developed tomography yielded good data quality and resolved even small amounts of hydrate saturation inside the sediment sample. The conversion algorithm transforming the spatial resistivity distribution into local hydrate saturation values yielded the best results using the Archie-var-phi relation. This approach considers the increasing hydrate phase as part of the sediment frame, metaphorically reducing the sample’s porosity. In addition, the tomographical measurements showed that fast lab based hydrate formation processes cause small crystallites to form which tend to recrystallize. Furthermore, hydrate dissociation experiments via depressurization were conducted in order to mimic the 2007/2008 Mallik field trial. It was observed that some patterns in gas and water flow could be reproduced, even though some setup related limitations arose. In two additional long-term experiments the feasibility and performance of CO2-CH4 hydrate exchange reactions were studied in LARS. The tomographical system was used to monitor the spatial hydrate distribution during the hydrate formation stage. During the subsequent CO2 injection, the tomographical array allowed to follow the CO2 migration front inside the sediment sample and helped to identify the CO2 breakthrough. KW - hydrate KW - Electrical Resistivity Tomography (ERT) KW - geophysics KW - Gashydrate KW - Elektrische Widerstandstomographie (ERT) KW - Geophysik Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89321 ER - TY - THES A1 - Seyberth, Karl T1 - Test einer neuen Methode zur Synthetisierung hydrathaltiger Sedimentproben und Charakterisierung des Hydrathabitus anhand seismischer Messungen T1 - Test of a new method for the synthesis of hydrate bearing sediment samples and characterization of the hydrate habitus based on seismic measurements N2 - Methanhydrate sind besonders in Verbindung mit den steigenden Weltmarktpreisen für Öl und Gas in den vergangenen Jahren mehr und mehr in den Fokus der Energiewirtschaft geraten, was zu einer starken Zunahme der angewandten Forschungsprojekte auf diesem Gebiet führte. Da Methanhydrat nur unter hohem Druck und niedrigen Temperaturen stabil ist, ist die Gewinnung natürlicher Proben für Laboruntersuchungen technisch sehr aufwendig und vor allem teuer. Zur Charakterisierung der Eigenschaften hydratführender Reservoire ist man häufig auf die Herstellung synthetischer Proben angewiesen. Die Eigenschaften der synthetisierten Proben sind dabei abhängig von der Herstellungsmethode und man ist noch immer auf der Suche nach Verfahren, mit denen sich möglichst „naturnahe“ Proben mit vertretbarem Aufwand erzeugen lassen. In der vorliegenden Arbeit wurde eine neue, relativ schnell durchführbare Methode getestet, die im Porenraum von Sedimenten schwimmende bzw. gefügestützende Hydrate bildet, wie sie in der Natur vorkommen. Gleichzeitig erzeugt sie eine gleichmäßige Verteilung des Hydrats über die Probe und bietet gute Kontrolle über den Hydratgehalt. Sie funktioniert wie folgt: Eine mit einer KCl-Lösung gesättigte Sedimentprobe wird zu einem bestimmten Teil ausgefroren und das übrige Wasser mit Methan verdrängt. Durch Anlegen eines Methandrucks im Stabilitätsbereich wird das Eis zu Methanhydrat umgesetzt. Im Anschluss wird die Probe erneut mit einer KCl-Lösung gesättigt. Anhand seismischer Messungen konnte bestätigt werden, dass Hydrat mit dem gewünschten Hydrathabitus erzeugt wurde. Des Weiteren wurde gezeigt, dass die eishaltigen Proben aufgrund ähnlicher physikalischer Eigenschaften bereits vor der Umsetzung des Eises zu Methanhydrat als Näherung für Proben mit Porenraumhydrat verwendet werden können. N2 - Due to the rising world market prices for oil and gas, the energy industry pays more and more attention to methane hydrates. This leads to a strong augmentation of applied research projects in this field of studies. As methane hydrates are only stable under large pressure and low temperatures, the recovery of samples is technically very complex and expensive. Hence, for the characterization of the properties of hydrate bearing reservoirs, usually synthetic samples are used. The properties of these synthesized samples depend on the production method and scientists are still searching for procedures that allow the synthesization of close to nature samples at a justifiable effort. In this paper, a relatively quickly performable new method was tested that produces hydrates floating in the pore space respectively grain supporting hydrates. These are the most common types of gas hydrates in natural environments. Furthermore the method forms a uniform distribution across the sample and allows a good control over the hydrate content. It works as follows: A sediment sample saturated with a KCl-solution is frozen until a certain ice content is reached and the remaining brine is pushed out with methane. Then the ice is converted into methane hydrate by the installation of methane pressure in the stability field. In the end the methane is replaced by a KCl-solution again. With the help of seismic measurements it could be proven that the hydrate showed the desired properties. Besides that it was shown that yet before the transformation of ice to methane hydrate one can use the ice-containing samples as an approximation for the hydrate-bearing samples. Both show similar physical properties. KW - Methanhydrat KW - methane hydrate KW - synthetic hydrate samples KW - synthetische Hydratproben KW - seismische Messungen KW - seismic measurements KW - Hydrathabitus KW - hydrate habitus Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81247 ER - TY - THES A1 - Helpa, Vanessa T1 - Interplay between mineral reaction and deformation via structural defects T1 - Wechselwirkung von Mineralreaktion und Deformation durch Strukturdefekte N2 - This thesis contains three experimental studies addressing the interplay between deformation and the mineral reaction between natural calcite and magnesite. The solid-solid mineral reaction between the two carbonates causes the formation of a magnesio-calcite precursor layer and a dolomite reaction rim in every experiment at isostatic annealing and deformation conditions. CHAPTER 1 briefly introduces general aspects concerning mineral reactions in nature and diffusion pathways for mass transport. Moreover, results of previous laboratory studies on the influence of deformation on mineral reactions are summarized. In addition, the main goals of this study are pointed out. In CHAPTER 2, the reaction between calcite and magnesite single crystals is examined at isostatic annealing conditions. Time series performed at a fixed temperature revealed a diffusion-controlled dolomite rim growth. Two microstructural domains could be identified characterized by palisade-shaped dolomite grains growing into the magnesite and granular dolomite growing towards calcite. A model was provided for the dolomite rim growth based on the counter-diffusion of CaO and MgO. All reaction products exhibited a characteristic crystallographic relationship with respect to the calcite reactant. Moreover, kinetic parameters of the mineral reaction were determined out of a temperature series at a fixed time. The main goal of the isostatic test series was to gain information about the microstructure evolution, kinetic parameters, chemical composition and texture development of the reaction products. The results were used as a reference to quantify the influence of deformation on the mineral reaction. CHAPTER 3 deals with the influence of non-isostatic deformation on dolomite and magnesio-calcite layer production between calcite and magnesite single crystals. Deformation was achieved by triaxial compression and by torsion. Triaxial compression up to 38 MPa axial stress at a fixed time showed no significant influence of stress and strain on dolomite formation. Time series conducted at a fixed stress yield no change in growth rates for dolomite and magnesio-calcite at low strains. Slightly larger magnesio-calcite growth rates were observed at strains above >0.1. High strains at similar stresses were caused by the activation of additional glide systems in the calcite single crystal and more mobile dislocations in the magnesio-calcite grains, providing fast diffusion pathways. In torsion experiments a gradual decrease in dolomite and magnesio-calcite layer thickness was observed at a critical shear strain. During deformation, crystallographic orientations of reaction products rearranged with respect to the external framework. A direct effect of the mineral reaction on deformation could not be recognized due to the relatively small reaction product widths. In CHAPTER 4, the influence of starting material microfabrics and the presence of water on the reaction kinetics was evaluated. In these experimental series polycrystalline material was in contact with single crystals or two polycrystalline materials were used as reactants. Isostatic annealing resulted in different dolomite and magnesio-calcite layer thicknesses, depending on starting material microfabrics. The reaction progress at the magnesite interface was faster with smaller magnesite grain size, because grain boundaries provided fast pathways for diffusion and multiple nucleation sites for dolomite formation. Deformation by triaxial compression and torsion yield lower dolomite rim thicknesses compared to annealed samples for the same time. This was caused by grain coarsening of polycrystalline magnesite during deformation. In contrast, magnesio-calcite layers tended to be larger during deformation, which triggered enhanced diffusion along grain boundaries. The presence of excess water had no significant influence on the reaction kinetics, at least if the reactants were single crystals. In CHAPTER 5 general conclusions about the interplay between deformation and the mineral reaction in the carbonate system are presented. Finally, CHAPTER 6 highlights possible future work in the carbonate system based on the results of this study. N2 - Die vorliegende Arbeit umfasst drei experimentelle Studien die sich mit der Wechselwirkung von Mineralreaktion und Deformation zwischen natürlichem Kalzit und Magnesit befassen. Die fest-fest Mineralreaktion zwischen den Karbonaten führt zur Entstehung einer Magnesio-Kalzit Vorläuferphase und zur Entstehung eines Dolomit Reaktionssaumes in allen durchge-führten Experimenten sowohl unter isostatischen Bedingungen als auch während der Defor-mation. Im ersten Kapitel werden die grundlegenden Aspekte hinsichtlich Mineralreaktionen in der Natur und Diffusion angeführt. Weiterhin werden Resultate von vorherigen Studien bezüglich des Einflusses von Deformation auf Mineralreaktionen zusammengefasst. Außerdem werden die Hauptziele dieser Studie aufgezeigt. Im zweiten Kapitel wird die Mineralreaktion zwischen Kalzit und Magnesit Einkristallen unter isostatischen Bedingungen untersucht. Zeitserien bei einer festgelegten Temperatur zeigten ein diffusionskontrolliertes Dolomitsaumwachstum. Die Mikrostruktur des Dolomitsaums ist durch zwei unterschiedliche Bereiche charakterisiert. Palisadenartige Dolomitkörner wachsen in den Magnesit und granulare Dolomitkörner wachsen in Richtung des Kalzits. Ein Model für das Dolomitsaumwachstum wurde angewandt, basierend auf der Gegendiffusion von CaO und MgO. Alle Reaktionsprodukte zeigten eine bestimmte kristallographische Beziehung in Hinblick auf den Kalzitreaktanten. Des Weiteren wurden die kinetischen Parameter für die Mineralreaktion durch Temperaturserien bei einer festen Versuchslaufzeit bestimmt. Das Hauptziel der isostatischen Testserie bestand darin Informationen über die mikrostrukturelle Entwicklung, die kinetischen Parameter, die chemische Zusammensetzung und die texturelle Entwicklung der Reaktionsprodukte zu gewinnen. Die Resultate dienten als Referenz um den Einfluss der Deformation auf die Mineralreaktion zu quantifizieren. Kapitel drei befasst sich mit dem Effekt von nicht-isostatischer Deformation auf die Bildungen von Dolomit und Magnesio-Kalzit zwischen Kalzit und Magnesit Einkristallen. Deformation wurde entweder durch triaxiale Kompression oder durch Torsion erreicht. Triaxiale Kompression bis zu 38 MPa axialer Spannung bei festgelegter Zeit zeigte keinen signifikanten Einfluss von Spannung und Verformung auf die Dolomitproduktion. Eine Zeitserie bei ähnlichen axialen Spannungen und geringen Verformungen resultierten in vergleichbaren Wachstumsraten für Dolomit und Magnesio-Kalzit wie unter isostatischen Bedingungen. Geringfügig schnellere Wachstumsraten für den Magnesio-Kalzit traten in Experimenten auf bei denen die Verformung größer als 0.1 war. Hohe Verformungen bei ähnlichen Spannungen wurde durch die Aktivierung zusätzlicher Gleitsysteme im Kalzit Einkristall und mobile Versetzungen im Magnesio-Kalzit erreicht, welche schnelle Wege für Diffusion bereitstellen. In Torsionsexperimenten wurde eine graduelle Abnahme der Dolomitsaumdicke und des Magnesio-Kalzits beim Überschreiten einer kritischen Scherverformung festgestellt. Während der Deformation kam es zu einer Umorientierung der kristallographischen Achsen von Dolomit und Magnesio-Kalzit hinsichtlich des externen Bezugsystems. Ein direkter Effekt der Mineralreaktion auf die Deformation konnte auf Grund der relative geringen Reaktionsproduktdi-cke nicht gesehen werden. Im vierten Kapitel wurden der Korngrößeneinfluss des Ausgangsmaterials sowie die Anwesenheit von Wasser auf die Reaktionskinetik getestet. In dieser Testserie wurde polykristallines Material in Kontakt zu Einkristallen gebracht oder zwei polykristalline Materialien wurden als Reaktanten benutzt. Isostatisches Ausheizen resultierte in verschiedenen Dolomitsaum- und Magnesio-Kalzitdicken in Abhängigkeit der Korngröße der Reaktanten. Bei kleinen Korngrößen des Magnesits war der Reaktionsfortschritt erhöht, da Korngrenzen Wege für schelle Diffusion boten und viele Nukleationskeime erlaubten. Im Gegensatz zu isostatischen Bedingungen führten triaxiale Kompression und Torsion zu geringen Dolomitsaumdi-cken. Die Ursache hierfür war auftretendes Kornwachstum im polykristallinen Magnesit während der Deformation. Für den Magnesio-Kalzit wurde ein beschleunigtes Wachstum während der Deformation festgestellt, da der Massentransport entlang von Korngrenzen begünstigt wurde. Die Reaktionskinetik zwischen zwei Einkristallen wurde durch die Anwesenheit von zusätzlichem Wasser nicht signifikant beeinflusst. Das fünfte Kapitel enthält die generellen Schlussfolgerungen die für die Wechselwirkung von Mineralreaktion und Deformation im Karbonatsystem getroffen werden konnten. Basierend auf den Resultaten dieser Studie zeigt Kapitel sechs abschließend auf, welche Möglichkeiten es für zukünftige Arbeiten im Karbonatsystem gibt. KW - carbonates KW - deformation KW - mineral reaction KW - Karbonate KW - Deformation KW - Mineralreaktion Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-90332 ER - TY - JOUR A1 - Gerya, Taras V. A1 - Stern, Robert J. A1 - Baes, Marzieh A1 - Sobolev, Stephan Vladimir A1 - Whattam, Scott A. T1 - Plate tectonics on the Earth triggered by plume-induced subduction initiation JF - Nature : the international weekly journal of science N2 - Scientific theories of how subduction and plate tectonics began on Earth-and what the tectonic structure of Earth was before this-remain enigmatic and contentious(1). Understanding viable scenarios for the onset of subduction and plate tectonics(2,3) is hampered by the fact that subduction initiation processes must have been markedly different before the onset of global plate tectonics because most present-day subduction initiation mechanisms require acting plate forces and existing zones of lithospheric weakness, which are both consequences of plate tectonics(4). However, plume-induced subduction initiation(5-9) could have started the first subduction zone without the help of plate tectonics. Here, we test this mechanism using high-resolution three-dimensional numerical thermomechanical modelling. We demonstrate that three key physical factors combine to trigger self-sustained subduction: (1) a strong, negatively buoyant oceanic lithosphere; (2) focused magmatic weakening and thinning of lithosphere above the plume; and (3) lubrication of the slab interface by hydrated crust. We also show that plume-induced subduction could only have been feasible in the hotter early Earth for old oceanic plates. In contrast, younger plates favoured episodic lithospheric drips rather than self-sustained subduction and global plate tectonics. Y1 - 2015 U6 - https://doi.org/10.1038/nature15752 SN - 0028-0836 SN - 1476-4687 VL - 527 IS - 7577 SP - 221 EP - + PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Tötzke, Christian A1 - Manke, Ingo A1 - Gaiselmann, Gerd A1 - Bohner, John A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Schmidt, Volker A1 - Banhart, Jens A1 - Lehnert, Werner T1 - A dedicated compression device for high resolution X-ray tomography of compressed gas diffusion layers JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - We present an experimental approach to study the three-dimensional microstructure of gas diffusion layer (GDL) materials under realistic compression conditions. A dedicated compression device was designed that allows for synchrotron-tomographic investigation of circular samples under well-defined compression conditions. The tomographic data provide the experimental basis for stochastic modeling of nonwoven GDL materials. A plain compression tool is used to study the fiber courses in the material at different compression stages. Transport relevant geometrical parameters, such as porosity, pore size, and tortuosity distributions, are exemplarily evaluated for a GDL sample in the uncompressed state and for a compression of 30 vol.%. To mimic the geometry of the flow-field, we employed a compression punch with an integrated channel-rib-profile. It turned out that the GDL material is homogeneously compressed under the ribs, however, much less compressed underneath the channel. GDL fibers extend far into the channel volume where they might interfere with the convective gas transport and the removal of liquid water from the cell. (C) 2015 AIP Publishing LLC. Y1 - 2015 U6 - https://doi.org/10.1063/1.4918291 SN - 0034-6748 SN - 1089-7623 VL - 86 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Obu, Jaroslav T1 - Effect of mass wasting on soil organic carbon storage and coastal erosion in permafrost environments T1 - Einfluss von Hangbewegungen auf Kohlenstoffspeicher und Küstenerosion in Permafrostgebieten N2 - Accelerated permafrost thaw under the warming Arctic climate can have a significant impact on Arctic landscapes. Areas underlain by permafrost store high amounts of soil organic carbon (SOC). Permafrost disturbances may contribute to increased release of carbon dioxide and methane to the atmosphere. Coastal erosion, amplified through a decrease in Arctic sea-ice extent, may also mobilise SOC from permafrost. Large expanses of permafrost affected land are characterised by intense mass-wasting processes such as solifluction, active-layer detachments and retrogressive thaw slumping. Our aim is to assess the influence of mass wasting on SOC storage and coastal erosion. We studied SOC storage on Herschel Island by analysing active-layer and permafrost samples, and compared non-disturbed sites to those characterised by mass wasting. Mass-wasting sites showed decreased SOC storage and material compaction, whereas sites characterised by material accumulation showed increased storage. The SOC storage on Herschel Island is also significantly correlated to catenary position and other slope characteristics. We estimated SOC storage on Herschel Island to be 34.8 kg C m-2. This is comparable to similar environments in northwest Canada and Alaska. Coastal erosion was analysed using high resolution digital elevation models (DEMs). Two LIDAR scanning of the Yukon Coast were done in 2012 and 2013. Two DEMs with 1 m horizontal resolution were generated and used to analyse elevation changes along the coast. The results indicate considerable spatial variability in short-term coastline erosion and progradation. The high variability was related to the presence of mass-wasting processes. Erosion and deposition extremes were recorded where the retrogressive thaw slump (RTS) activity was most pronounced. Released sediment can be transported by longshore drift and affects not only the coastal processes in situ but also along adjacent coasts. We also calculated volumetric coastal erosion for Herschel Island by comparing a stereo-photogrammetrically derived DEM from 2004 with LIDAR DEMs. We compared this volumetric erosion to planimetric erosion, which was based on coastlines digitised from satellite imagery. We found a complex relationship between planimetric and volumetric coastal erosion, which we attribute to frequent occurrence of mass-wasting processes along the coasts. Our results suggest that volumetric erosion corresponds better with environmental forcing and is more suitable for the estimation of organic carbon fluxes than planimetric erosion. Mass wasting can decrease SOC storage by several mechanisms. Increased aeration following disturbance may increase microbial activity, which accelerates organic matter decomposition. New hydrological conditions that follow the mass wasting event can cause leaching of freshly exposed material. Organic rich material can also be directly removed into the sea or into a lake. On the other hand the accumulation of mobilised material can result in increased SOC storage. Mass-wasting related accumulations of mobilised material can significantly impact coastal erosion in situ or along the adjacent coast by longshore drift. Therefore, the coastline movement observations cannot completely resolve the actual sediment loss due to these temporary accumulations. The predicted increase of mass-wasting activity in the course of Arctic warming may increase SOC mobilisation and coastal erosion induced carbon fluxes. N2 - Die Erwärmung des arktischen Klimas beschleunigt das Tauen des Permafrosts. Das kann einen erheblichen Einfluss auf arktische Landschaften haben. Permafrostböden speichern große Mengen Kohlenstoff, der aufgrund von Umlagerungsprozessen wie beispielsweise Massenversatz mobilisiert und als Kohlendioxid oder Methan freigesetzt werden kann. Der Kohlenstoff im Boden kann auch durch Küstenerosion mobilisiert werden, die durch den Rückgang des arktischen Meereises und höhere Meerwassertemperaturen künftig stark zunehmen wird. Große Teile der arktischen Permafrostgebiete werden durch intensive Massenversatzprozesse wie Solifluktion, Rutschungen in der saisonalen Auftauschicht (active layer detachments) und rückschreitende Taurutschungen (retrogressive thaw slumps) gekennzeichnet. Unser Ziel ist es, den Einfluss dieser Massenbewegungen auf Kohlenstoffspeicher und Küstenerosion zu bewerten. Wir haben Auftauschicht- und Permafrostproben untersucht, um den Kohlenstoffspeicher für Herschel Island zu ermitteln. Wir verglichen ungestörtes Terrain mit durch Massenversatz gekennzeichnetem Terrain. Letzteres zeigte verringerte Bodenkohlenstoffspeicher und Materialverdichtung. Durch Akkumulation organischen Materials gekennzeichnete Lagen zeigten eine Zunahme des Kohlenstoffpeichers. Der Bodenkohlenstoffspeicher auf Herschel Insel korreliert außerdem deutlich mit der Lage in Senken und der Hangneigung. Der Kohlenstoffspeicher im Boden von Herschel Island ist etwa so hoch wie in vergleichbaren Landschaften im Nordwesten Kanadas und Alaskas. Wir schätzen ihn auf 34,8 kg C m-2. Wir ermittelten Küstenerosionsraten mit hochauflösenden Digitalen Geländemodellen (DGM). Dazu benutzten wir zwei LIDAR Aufnahmen der Yukon Küste aus den Jahren 2012 und 2013. Zwei DGMs mit 1 m horizontaler Auflösung wurden erzeugt und verwendet, um die Höhenunterschiede entlang der Küste zu analysieren. Wir fanden eine erhebliche räumliche Variabilität in kurzfristigen Küstenerosionsraten. Wir erklärten die hohe Variabilität mit der räumlichen Heterogenität des Vorkommens von Massenversatzprozessen. Besonders die sogenannten retrogressive thaw slumps bewirkten extrem hohe Erosionsraten an einigen Küstenabschnitten. Durch Strandversetzung wird erodiertes Sediment die Küste entlang transportiert und beeinflusst so nicht nur lokale Küstenprozesse, sondern auch benachbarte Küstenabschnitte. Um die längerfristige Entwicklung der Küste einschätzen zu können, haben wir volumetrische Erosionsraten aus dem Vergleich eines stereophotogrammetrisch abgeleiteten DGM aus dem Jahr 2004 mit unseren LIDAR DGMs errechnet. Planimetrische Erosionsraten wurden anhand von digitalisierten Küstenlinien aus Satellitenbildern berechnet. So konnte auch der Einfluss von volumetrischer und planimetrischer Erosion eingeschätzt werden. Wir fanden komplexe Zusammenhänge zwischen planimetrischer und volumetrischer Küstenerosion, die wir auf das gehäufte Auftreten von Massenversatzprozessen entlang einiger Küstenabschnitte zurückführen. Die Ergebnisse legen nahe, dass volumetrische Erosionsraten den beobachteten Umweltbedingungen besser entsprechen als planimetrische Erosionsraten und somit besser geeignet sind zur Einschätzung organischer Kohlenstoffflüsse in Permafrostgebieten entlang der arktischen Küsten. Massenversatz kann den Kohlenstoffspeicher im Boden mit verschiedenen Mechanismen verringern. Erhöhte Belüftung kann die mikrobielle Aktivität erhöhen, die den Abbau organischer Materie beschleunigt. Durch veränderte hydrologische Bedingungen nach Massenversatz können Stoffe aus der Auftauschicht ausgewaschen werden. Organikreiche Stoffe können auch direkt ins einem Meer in einen See erodiert werden. Andererseits kann die Akkumulation von umgelagertem Material zu einer Erhöhung des Bodenkohlenstoffspeichers an anderer Stelle führen. Die Akkumulation von Material aus Massenversatz kann erhebliche Auswirkungen auf die lokale Küstenerosion, durch Strandversetzung aber auch auf angrenzende Küstenabschnitte haben. Allein durch Beobachtung der Veränderung von Küstenlinien kann aufgrund solcher temporärer Ansammlungen die Einschätzung des tatsächlichen Sedimentverlustes pro Küstenabschnitt nicht präzise wiedergegeben werden. Im Zuge der prognostizierten Erwärmung der Arktis und der damit verbundene Zunahme von Massenversatzprozessen und Küstenerosion wird sich die Mobilisierung von Bodenkohlenstoff aus Permafrost zukünftig beschleunigen. KW - mass wasting KW - soil organic carbon KW - coastal erosion KW - Massenversatzprozesse KW - Kohlenstoffspeicher KW - Küstenerosion Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-90599 ER - TY - JOUR A1 - Kwiatek, Grzegorz A1 - Martinez-Garzon, Patricia A1 - Dresen, Georg A1 - Bohnhoff, Marco A1 - Sone, Hiroki A1 - Hartline, Craig T1 - Effects of long-term fluid injection on induced seismicity parameters and maximum magnitude in northwestern part of The Geysers geothermal field JF - Journal of geophysical research : Solid earth N2 - The long-term temporal and spatial changes in statistical, source, and stress characteristics of one cluster of induced seismicity recorded at The Geysers geothermal field (U.S.) are analyzed in relation to the field operations, fluid migration, and constraints on the maximum likely magnitude. Two injection wells, Prati-9 and Prati-29, located in the northwestern part of the field and their associated seismicity composed of 1776 events recorded throughout a 7year period were analyzed. The seismicity catalog was relocated, and the source characteristics including focal mechanisms and static source parameters were refined using first-motion polarity, spectral fitting, and mesh spectral ratio analysis techniques. The source characteristics together with statistical parameters (b value) and cluster dynamics were used to investigate and understand the details of fluid migration scheme in the vicinity of injection wells. The observed temporal, spatial, and source characteristics were clearly attributed to fluid injection and fluid migration toward greater depths, involving increasing pore pressure in the reservoir. The seasonal changes of injection rates were found to directly impact the shape and spatial extent of the seismic cloud. A tendency of larger seismic events to occur closer to injection wells and a correlation between the spatial extent of the seismic cloud and source sizes of the largest events was observed suggesting geometrical constraints on the maximum likely magnitude and its correlation to the average injection rate and volume of fluids present in the reservoir. KW - fluid-induced seismicity KW - maximum magnitude KW - reservoir characterization KW - source parameters KW - passive seismic monitoring Y1 - 2015 U6 - https://doi.org/10.1002/2015JB012362 SN - 2169-9313 SN - 2169-9356 VL - 120 IS - 10 SP - 7085 EP - 7101 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Zhou, Xiqiang A1 - Chen, Daizhao A1 - Dong, Shaofeng A1 - Zhang, Yanqiu A1 - Guo, Zenghui A1 - Wei, Hengye A1 - Yu, Hao T1 - Diagenetic barite deposits in the Yurtus Formation in Tarim Basin, NW China: Implications for barium and sulfur cycling in the earliest Cambrian JF - Precambrian research N2 - Barite concretions and bands are widely distributed in black shale-chert horizons in the Yurtus Formation of Lower Cambrian in Aksu area, northwestern Tarim Basin, NW China. They mainly consist of coarse-grained anhedral to euhedral barite crystals with minor dolomites and pyrites. Petrological features indicate these concretions grew from the porewater in unconsolidated sediments at shallow burial below sediment-water interface. The slight deviation of Sr-87/Sr-86 ratios (0.7083 to 0.7090) and significant elevated delta S-34 values (56.8-76.4 parts per thousand CDT) of barite samples with respect to those of the Early Cambrian seawater further support that barite deposits precipitated from the enclosed porewater in sediment column, which evolved from the penecontemporaneous seawater with weak interaction with the host fine-grained siliciclastic sediments and highly-depleted sulfate in response to prolonged strong bacterial sulfate reduction without necessary renewal. The abundant organic matters in the basal Yurtus Formation should have facilitated developing sulfate-depleted methanogenesis zone and sulfate-methane transition zone (SMTZ) slightly after deposition. Therefore, barite deposits in the Yurtus Formation most likely resulted from diagenetic barium cycling and persistently grew from the porewater in the static SMTZ with a low sedimentation rate in the Early Cambrian. In comparison with the distribution of sedimentary barites in geological records, we tentatively proposed that a transition in diagenetic barium cycling and associated mineralization may have occurred from the Precambrian to Cambrian periods; this scenario may be causally linked to the changes in marine ecology (the advent of mesozooplankton and associated faecal pellet) and geochemistry (the increase of seawater sulfate concentration). Thus, the occurrence of diagenetic barite deposits in the Yurtus Formation implies that diagenetic barium cycling and more effective scavenging of barium from CH4- and Ba-rich porewaters within sediments might have become an nonnegligible process in continental margin areas, at least, since the earliest Cambrian, which could have significantly impacted the marine barium cycling. (C) 2015 Elsevier B.V. All rights reserved. KW - Barite concretion KW - Diagenetic barium cycling KW - Earliest Cambrian KW - Yurtus Formation KW - Tarim Basin, NW China Y1 - 2015 U6 - https://doi.org/10.1016/j.precamres.2015.03.006 SN - 0301-9268 SN - 1872-7433 VL - 263 SP - 79 EP - 87 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rosenwinkel, Swenja A1 - Korup, Oliver A1 - Landgraf, Angela A1 - Dzhumabaeva, Atyrgul T1 - Limits to lichenometry JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Lichenometry is a straightforward and inexpensive method for dating Holocene rock surfaces. The rationale is that the diameter of the largest lichen scales with the age of the originally fresh rock surface that it colonised. The success of the method depends on finding the largest lichen diameters, a suitable lichen-growth model, and a robust calibration curve. Recent critique of the method motivates us to revisit the accuracy and uncertainties of lichenometry. Specifically, we test how well lichenometry is capable of resolving the ages of different lobes of large active rock glaciers in the Kyrgyz Tien Shan. We use a bootstrapped quantile regression to calibrate local growth curves of Xanthoria elegans, Aspicilia tianshanica, and Rhizocarpon geographicum, and report a nonlinear decrease in dating accuracy with increasing lichen diameter. A Bayesian type of an analysis of variance demonstrates that our calibration allows discriminating credibly between rock-glacier lobes of different ages despite the uncertainties tied to sample size and correctly identifying the largest lichen thalli. Our results also show that calibration error grows with lichen size, so that the separability of rock-glacier lobes of different ages decreases, while the tendency to assign coeval ages increases. The abundant young (<200 yr) specimen of fast-growing X elegans are in contrast with the fewer, slow-growing, but older (200-1500 yr) R. geographicum and A. tianshanica, and record either a regional reactivation of lobes in the past 200 years, or simply a censoring effect of lichen mortality during early phases of colonisation. The high variance of lichen sizes captures the activity of rock-glacier lobes, which is difficult to explain by regional climatic cooling or earthquake triggers alone. Therefore, we caution against inferring palaeoclimatic conditions from the topographic position of rock-glacier lobes. We conclude that lichenometry works better as a tool for establishing a relative, rather than an absolute, chronology of rock-glacier lobes in the northern Tien Shan. (C) 2015 Elsevier Ltd. All rights reserved. KW - Lichenometry KW - Rock glacier KW - Absolute age dating KW - Kyrgyzstan KW - Tien Shan Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.10.031 SN - 0277-3791 VL - 129 SP - 229 EP - 238 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ulloa, Hector A1 - Irourne, Andres A1 - Picco, Lorenzo A1 - Korup, Oliver A1 - Lenzi, Mario Aristide A1 - Mao, Luca A1 - Ravazzolo, Diego T1 - Massive biomass flushing despite modest channel response in the Rayas River following the 2008 eruption of Chaiten volcano, Chile JF - Geomorphology : an international journal on pure and applied geomorphology N2 - The 2008 eruption of Chaiten volcano in southern Chile severely impacted several densely forested river catchments by supplying excess pyroclastic sediment to the channel networks. Our aim is to substantiate whether and how channel geometry and forest stands changed in the Rayas River following the sudden input of pyroclastic sediment. We measured the resulting changes to channel geometry and riparian forest stands along 17.6 km of the impacted gravel-bed Rayas River (294 km(2)) from multiple high-resolution satellite images, aerial photographs, and fieldwork to quantify yield volume characteristics of the forest stands. Limited channel changes during the last 60 years before the eruption reflect a dynamic equilibrium condition of the river corridor, despite the high annual precipitation and the sediment supply from Chaiten and Michinmahuida volcanoes in the headwaters. Images taken in 1945, 2004, and 2005 show that total size of the vegetated channel islands nearly doubled between 1945 and 2004 and remained unchanged between 2004 and 2005. Pyroclastic sediment entering the Rayas River after the 2008 eruption caused only minor average channel widening (7%), but killed all island vegetation in the study reach. Substantial shifts in the size distribution of in-channel vegetation patches reflect losses in total island area of 46% from 2005 to 2009 and an additional 34% from 2009 to 2012. The estimated pulsed release of organic carbon into the channel, mainly in the form of large wood from obliterated island and floodplain forests, was 78-400 tC/km/y and surpasses most documented yields from small mountainous catchments with similar rainfall, forest cover, and disturbance history, while making up between 20% and 60% of the annual carbon burial rate of fluvial sediments in the northern Patagonian fjords. We conclude that the carbon footprint of the 2008 Chaiten eruption on the Rayas River was more significant than the measured geomorphic impacts on channel geometry for the first five years following disturbance. The modest post-eruptive geomorphic response in this river is a poor indicator of its biogeochemical response. (C) 2015 Elsevier B.V. All rights reserved. KW - Chaiten volcano KW - Forest disturbance KW - Channel island KW - Organic carbon Y1 - 2015 U6 - https://doi.org/10.1016/j.geomorph.2015.09.019 SN - 0169-555X SN - 1872-695X VL - 250 SP - 397 EP - 406 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Blöthe, Jan Henrik A1 - Korup, Oliver A1 - Schwanghart, Wolfgang T1 - Large landslides lie low: Excess topography in the Himalaya-Karakoram ranges JF - Geology N2 - Mass wasting is an important process for denuding hillslopes and lowering ridge crests in active mountain belts such as the Himalaya-Karakoram ranges (HKR). Such a high-relief landscape is likely to be at its mechanical threshold, maintained by competing rapid rock uplift, river incision, and pervasive slope failure. We introduce excess topography, Z(E), for quantifying potentially unstable rock-mass volumes inclined at angles greater than a specified threshold angle. We find that Z(E) peaks along major fluvial and glacial inner gorges, which is also where the majority of 492 large (>0.1 km(2)) rock-slope failures occur in the Himalaya's largest cluster of documented Pleistocene to Holocene bedrock landslides. Our data reveal that bedrock landslides in the HKR chiefly detached from near or below the median elevation, whereas glaciers and rock glaciers occupy higher-elevation bands almost exclusively. Less than 10% of the area of the HKR is upslope of glaciers, such that possible censoring of evidence of large bedrock landslides above the permanent snow line barely affects this finding. Bedrock landslides appear to preferentially undermine topographic relief in response to fluvial and glacial incision along inner gorges, unless more frequent and smaller undetected failures, or rigorous (peri-)glacial erosion, compensate for this role at higher elevation. Either way, the distinct patterns of excess topography and large bedrock landsliding in the HKR juxtapose two stacked domains of landslide and (peri-)glacial erosion that may respond to different time scales of perturbation. Our findings call for more detailed analysis of vertical erosional domains and their geomorphic coupling in active mountain belts. Y1 - 2015 U6 - https://doi.org/10.1130/G36527.1 SN - 0091-7613 SN - 1943-2682 VL - 43 IS - 6 SP - 523 EP - 526 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Philips, Andrea A1 - Walz, Ariane A1 - Bergner, Andreas G. N. A1 - Gräff, Thomas A1 - Heistermann, Maik A1 - Kienzler, Sarah A1 - Korup, Oliver A1 - Lipp, Torsten A1 - Schwanghart, Wolfgang A1 - Zeilinger, Gerold T1 - Immersive 3D geovisualization in higher education JF - Journal of geography in higher education N2 - In this study, we investigate how immersive 3D geovisualization can be used in higher education. Based on MacEachren and Kraak's geovisualization cube, we examine the usage of immersive 3D geovisualization and its usefulness in a research-based learning module on flood risk, called GEOSimulator. Results of a survey among participating students reveal benefits, such as better orientation in the study area, higher interactivity with the data, improved discourse among students and enhanced motivation through immersive 3D geovisualization. This suggests that immersive 3D visualization can effectively be used in higher education and that 3D CAVE settings enhance interactive learning between students. KW - immersive 3D geovisualization KW - 3D CAVE KW - higher education KW - learning success KW - student survey KW - flood risk Y1 - 2015 U6 - https://doi.org/10.1080/03098265.2015.1066314 SN - 0309-8265 SN - 1466-1845 VL - 39 IS - 3 SP - 437 EP - 449 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Meyer, Nele Kristin A1 - Schwanghart, Wolfgang A1 - Korup, Oliver A1 - Nadim, F. T1 - Roads at risk BT - traffic detours from debris flows in southern Norway JF - Natural hazards and earth system sciences N2 - Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods. Y1 - 2015 U6 - https://doi.org/10.5194/nhess-15-985-2015 SN - 1561-8633 VL - 15 IS - 5 SP - 985 EP - 995 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Stolle, Amelie A1 - Langer, Maria A1 - Blöthe, Jan Henrik A1 - Korup, Oliver T1 - On predicting debris flows in arid mountain belts JF - Global and planetary change N2 - The use of topographic metrics for estimating the susceptibility to, and reconstructing the characteristics of, debris flows has a long research tradition, although largely devoted to humid mountainous terrain. The exceptional 2010 monsoonal rainstorms in the high-altitude mountain desert of Ladakh and Zanskar, NW India, were a painful reminder of how susceptible arid regions are to rainfall-triggered flash floods, landslides, and debris flows. The rainstorms of August 4-6 triggered numerous debris flows, killing 182 people, devastating 607 houses, and more than 10 bridges around Ladakh's capital of Leh. The lessons from this disaster motivated us to revisit methods of predicting (a) flow parameters such as peak discharge and maximum velocity from field and remote sensing data, and (b) the susceptibility to debris flows from catchment morphometry. We focus on quantifying uncertainties tied to these approaches. Comparison of high-resolution satellite images pre- and post-dating the 2010 rainstorm reveals the extent of damage and catastrophic channel widening. Computations based on these geomorphic markers indicate maximum flow velocities of 1.6-6.7 m s(-1) with runout of up to similar to 10 km on several alluvial fans that sustain most of the region's settlements. We estimate median peak discharges of 310-610 m(3) s(-1), which are largely consistent with previous estimates. Monte Carlo-based error propagation for a single given flow-reconstruction method returns a variance in discharge similar to one derived from juxtaposing several different flow reconstruction methods. We further compare discriminant analysis, classification tree modelling, and Bayesian logistic regression to predict debris-flow susceptibility from morphometric variables of 171 catchments in the Ladakh Range. These methods distinguish between fluvial and debris flow-prone catchments at similar success rates, but Bayesian logistic regression allows quantifying uncertainties and relationships between potential predictors. We conclude that, in order to be robust and reliable, morphometric reconstruction of debris-flow properties and susceptibility requires careful assessment and reporting of errors and uncertainties. (C) 2015 Elsevier B.V. All rights reserved. KW - debris flow KW - peak discharge KW - channel geometry KW - geomorphometry KW - Bayesian logistic regression KW - Transhimalaya Y1 - 2015 U6 - https://doi.org/10.1016/j.gloplacha.2014.12.005 SN - 0921-8181 SN - 1872-6364 VL - 126 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Motuza, Gediminas A1 - Sliaupa, Saulius A1 - Timmerman, Martin Jan T1 - Geochemistry and Ar-40/Ar-39 age of Early Carboniferous dolerite sills in the southern Baltic Sea JF - Estonian journal of earth sciences N2 - The Early Carboniferous magmatic event in the southern Baltic Sea is manifested by dolerite intrusions. The presumable area in which the dolerite intrusions occur ranges from 30 to 60 km in east-west direction, and is about 100 km in north-south direction. The dolerites were sampled in well D1-1 and investigated by applying chemical analysis and Ar-40/Ar-39 step-heating dating. Dolerites are classified as alkali and sodic, characterized by high TiO2 (3.92, 3.99 wt%) and P2O5 (1.67, 1.77 wt%) and low MgO (4.89, 4.91 wt%) concentrations, enriched in light rare earth elements, originated from an enriched mantle magma source and emplaced in a continental rift tectonic setting. The 351 +/- 11 Ma Ar-40/Ar-39 plateau age for groundmass plagioclase indicates a considerable age gap with the 310-250 Ma magmatism in southern Scandinavia and northern Germany. The magmatic rocks in the Baltic Sedimentary Basin are coeval with alkaline intrusions of NE Poland. Both magmatic provinces lie in the northwestward prolongation of the Pripyat-Dnieper-Donetsk Rift (370-359 Ma) and may constitute a later phase of magmatic activity of this propagating rift system. KW - dolerite KW - rifting KW - Carboniferous KW - argon dating KW - Baltic Sea Y1 - 2015 U6 - https://doi.org/10.3176/earth.2015.30 SN - 1736-4728 SN - 1736-7557 VL - 64 IS - 3 SP - 233 EP - 248 PB - Estonian Academy Publ. CY - Tallinn ER - TY - JOUR A1 - Kreibich, Heidi A1 - Bubeck, Philip A1 - Van Vliet, Mathijs A1 - De Moel, Hans T1 - A review of damage-reducing measures to manage fluvial flood risks in a changing climate JF - Mitigation and adaptation strategies for global change : an international journal devoted to scientific, engineering, socio-economic and policy responses to environmental change N2 - Damage due to floods has increased during the last few decades, and further increases are expected in several regions due to climate change and growing vulnerability. To address the projected increase in flood risk, a combination of structural and non-structural flood risk mitigation measures is considered as a promising adaptation strategy. Such a combination takes into account that flood defence systems may fail, and prepares for unexpected crisis situations via land-use planning and private damage reduction, e.g. via building precautionary measures, and disaster response. However, knowledge about damage-reducing measures is scarce and often fragmented since based on case studies. For instance, it is believed that private precautionary measures, like shielding with water shutters or building fortification, are especially effective in areas with frequent flood events and low flood water levels. However, some of these measures showed a significant damage-reducing effect also during the extreme flood event in 2002 in Germany. This review analyses potentials of land-use planning and private flood precautionary measures as components of adaptation strategies for global change. Focus is on their implementation, their damage-reducing effects and their potential contribution to address projected changes in flood risk, particularly in developed countries. KW - Climate adaptation KW - Land-use planning KW - Damage reduction KW - Precaution KW - Risk zoning KW - Flood Y1 - 2015 U6 - https://doi.org/10.1007/s11027-014-9629-5 SN - 1381-2386 SN - 1573-1596 VL - 20 IS - 6 SP - 967 EP - 989 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Krieger, Lars A1 - Grigoli, Francesco T1 - Optimal reorientation of geophysical sensors: A quaternion- based analytical solution JF - Geophysics N2 - One of the most critical problems affecting geophysical data acquisition procedures is related to the misorientation of multicomponent sensors with respect to a common reference system (e.g., geographic north). In many applications, misoriented sensors affect data analysis procedures, leading to errors in results and interpretations. These problems generally occur in applications where the orientation of the sensor cannot be actively controlled and is not known a priori, e.g., geophysical sensors deployed in borehole installations or on the seafloor. We have developed a quaternion-based method for the optimal reorientation of multicomponent geophysical sensors. In contrast to other approaches, we took into account the full time-series record from all sensor components. Therefore, our method could be applied to all time-series data and was not restricted to a certain type of geophysical sensor. Our method allows the robust calculation of relative reorientations between two-component or three-component sensors. By using a reference sensor in an iterative process, this result can be extended to the estimation of absolute sensor orientations. In addition to finding an optimal solution for a full 3D sensor rotation, we have established a rigorous scheme for the estimation of uncertainties of the resulting orientation parameters. We tested the feasibility and applicability of our method using synthetic data examples for a vertical seismic profile and an ocean bottom seismometer array. We noted that the quaternion-based reorientation method is superior to the standard approach of a single-parameter estimation of rotation angles. Y1 - 2015 U6 - https://doi.org/10.1190/GEO2014-0095.1 SN - 0016-8033 SN - 1942-2156 VL - 80 IS - 2 SP - F19 EP - F30 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - JOUR A1 - Panitz, Sina A1 - Cortese, Giuseppe A1 - Neil, Helen L. A1 - Diekmann, Bernhard T1 - A radiolarian-based palaeoclimate history of Core Y9 (Northeast of Campbell Plateau, New Zealand) for the last 160 kyr JF - Marine micropaleontology N2 - Sea-surface temperatures (SSTs) based on radiolarian assemblage changes are estimated for the last 160 kyr, from a sediment core (Y9) recovered from Pukaki Saddle, northeast of Campbell Plateau. Site Y9 lies beneath Subantarctic Surface Water (SAW) immediately to the north of the Subantarctic Front (SAF), which in this region is bathymetrically constrained by the edges of Campbell Plateau and defines the northern boundary of the Antarctic Circumpolar Current (ACC). Radiolarian assemblages are characterised by an exceptionally high abundance of the Antarctic to subantarctic species Antarctissa spp. (up to 68%), especially during glacial intervals. SST estimates are derived using Factor Analysis and the Modern Analog Technique. Both methods capture the glacial-interglacial (G-I) pattern. The SST reconstructions show the changing relative influence of distinct water masses during the past G-I cycle, with major temperature variations of the order of 7-9 degrees C at glacial Terminations. Glacials (marine isotope stages (MIS) 6 and 2) are associated with particularly cool SSTs that are indicative of a more vigorous SAF/ACC and an enhancement of the inflow through Pukaki Saddle and/or frequent development of cold-core eddies at the SAF. By contrast, the influence of warmer waters and relaxation of the ACC during interglacials can be inferred from temperatures slightly warmer (e.g., mid-Holocene) and/or comparable to present day (e.g., MIS 5e). During these intervals, relatively warmer temperatures most likely indicate a higher warmcore eddy activity due to a strengthened Subtropical Front and/or a weakened inflow of cool water through Pukaki Saddle and/or an increased stratification in the Campbell Plateau region. Furthermore, the SST record is characterised by an abrupt warming at ca. 10 kyr (i.e., Termination l), the occurrence of a reversal at Termination I, and a warming event at the end of MIS 4, coinciding with the A4 event in the Byrd ice core. These characteristics, together with the pronounced G-I cycle shown by the SST estimates, suggest that Site Y9 is influenced by major oceanographic changes in the SW Pacific and responds to thermal changes at high southern latitudes. (C) 2014 Elsevier B.V. All rights reserved. KW - Radiolaria KW - Palaeotemperature KW - Subantarctic Front KW - Antarctic Circumpolar Current KW - Pacific Ocean Y1 - 2015 U6 - https://doi.org/10.1016/j.marmicro.2014.12.003 SN - 0377-8398 SN - 1872-6186 VL - 116 SP - 1 EP - 14 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mishra, Praveen Kumar A1 - Prasad, Sushma A1 - Anoop, A. A1 - Plessen, Birgit A1 - Jehangir, Arshid A1 - Gaye, Birgit A1 - Menzel, Philip A1 - Weise, Stephan M. A1 - Yousuf, Abdul R. T1 - Carbonate isotopes from high altitude Tso Moriri Lake (NW Himalayas) provide clues to late glacial and Holocene moisture source and atmospheric circulation changes JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - High resolution isotopic (delta O-18 and delta C-13) investigations on endogenic carbonates (calcite/aragonite) from Tso Moriri Lake, NW Himalaya show dramatic fluctuations during the late glacial and the early Holocene, and a persistent enrichment trend during the late Holocene. Changes in this lake are largely governed by the [input (meltwater + monsoon precipitation)/evaporationj (WE) ratio, also reflected in changes in the carbonate mineralogy with aragonite being formed during periods of lowest I/E. Using new isotopic data on endogenic carbonates in combination with the available data on geochemistry, mineralogy, and reconstructed mean annual precipitation, we demonstrate that the late glacial and early Holocene carbonate delta O-18 variability resulted from fluctuating Indian summer monsoon (ISM) precipitation in NW Himalaya. This region experienced increasing ISM precipitation between ca. 13.1 and 11.7 cal ka and highest ISM precipitation during the early Holocene (11.2-8.5 cal ka). However, during the late Holocene, evaporation was the dominant control on the carbonate delta O-18. Regional comparison of reconstructed hydrological changes from Tso Moriri Lake with other archives from the Asian summer monsoon and westerlies domain shows that the intensified westerly influence that resulted in higher lake levels (after 8 cal ka) in central Asia was not strongly felt in NW Himalaya. (C) 2015 Elsevier B.V. All rights reserved. KW - Carbonates KW - Holocene KW - Indian summer monsoon KW - Isotopes KW - Tso Moriri Lake Y1 - 2015 U6 - https://doi.org/10.1016/j.palaeo.2015.02.031 SN - 0031-0182 SN - 1872-616X VL - 425 SP - 76 EP - 83 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Barthold, Frauke Katrin A1 - Woods, Ross A. T1 - Stormflow generation: A meta-analysis of field evidence from small, forested catchments JF - Water resources research N2 - Combinations of runoff characteristics are commonly used to represent distinct conceptual models of stormflow generation. In this study, three runoff characteristics: hydrograph response, time source of runoff water, and flow path are used to classify catchments. Published data from the scientific literature are used to provide evidence from small, forested catchments. Each catchment was assigned to one of the eight conceptual models, depending on the combination of quick/slow response, old/new water, and overland/subsurface flow. A standard procedure was developed to objectively diagnose the predominant conceptual model of stormflow generation for each catchment and assess its temporal and spatial support. The literature survey yielded 42 catchments, of which 30 catchments provide a complete set of qualitative runoff characteristics resulting in one of the eight conceptual models. The majority of these catchments classify as subsurface flow path dominated. No catchments were found for conceptual models representing combinations of quick response-new water-subsurface flow (SSF), slow-new-SSF, slow-old-overland flow (OF) nor new-slow-OF. Of the 30 qualitatively classified catchments, 24 provide a complete set of quantitative measures. In summary, the field support is strong for 19 subsurface-dominated catchments and is weak for 5 surface flow path dominated catchments (six catchments had insufficient quantitative data). Two alternative explanations exist for the imbalance of field support between the two flow path classes: (1) the selection of research catchments in past field studies was mainly to explain quick hydrograph response in subsurface dominated catchments; (2) catchments with prevailing subsurface flow paths are more common in nature. We conclude that the selection of research catchments needs to cover a wider variety of environmental conditions which should lead to a broader, and more widely applicable, spectrum of resulting conceptual models and process mechanisms. This is a prerequisite in studies where catchment organization and similarity approaches are used to develop catchment classification systems in order to regionalize stormflow. Y1 - 2015 U6 - https://doi.org/10.1002/2014WR016221 SN - 0043-1397 SN - 1944-7973 VL - 51 IS - 5 SP - 3730 EP - 3753 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ferrero, Silvio A1 - Wunder, Bernd A1 - Walczak, Katarzyna A1 - Ziemann, Martin Andreas T1 - Preserved near ultrahigh-pressure melt from continental crust subducted to mantle depths JF - Geology N2 - Remnants of hydrous melt formed at mantle depths have been identified and characterized within high-pressure leucogranulites of the Orlica-Snieznik Dome (Bohemian Massif, central Europe). They occur as nanogranites in garnet formed via partial melting of granitoids during the Variscan orogeny. Melt composition and H2O content have been investigated in situ after experimental re-homogenization of the nanogranites, and are consistent with melts produced experimentally from crustal lithologies at mantle depths. This is the first geochemical study of melt inclusions from natural crustal rocks equilibrated close to the stability field of coesite, shedding light on how continental crust melts during deep subduction. Whereas decompressional melting is commonly invoked for deeply subducted crustal lithologies, melting occurred near or at the metamorphic peak pressure in the Orlica-Snieznik granulites. Melting of deeply subducted crustal rocks significantly modifies the rheology and thus promotes fast exhumation: this process has a critical influence on the geodynamic evolution of subduction-collision orogens as well as crustal differentiation at depth. Y1 - 2015 U6 - https://doi.org/10.1130/G36534.1 SN - 0091-7613 SN - 1943-2682 VL - 43 IS - 5 SP - 447 EP - 450 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Bösche, Nina Kristine A1 - Rogass, Christian A1 - Lubitz, Christin A1 - Brell, Maximilian A1 - Herrmann, Sabrina A1 - Mielke, Christian A1 - Tonn, Sabine A1 - Appelt, Oona A1 - Altenberger, Uwe A1 - Kaufmann, Hermann T1 - Hyperspectral REE (Rare Earth Element) Mapping of Outcrops-Applications for Neodymium Detection JF - Remote sensing N2 - In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces. Y1 - 2015 U6 - https://doi.org/10.3390/rs70505160 SN - 2072-4292 VL - 7 IS - 5 SP - 5160 EP - 5186 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mulyukova, Elvira A1 - Steinberger, Bernhard A1 - Dabrowski, Marcin A1 - Sobolev, Stephan Vladimir T1 - Survival of LLSVPs for billions of years in a vigorously convecting mantle: Replenishment and destruction of chemical anomaly JF - Journal of geophysical research : Solid earth N2 - We study segregation of the subducted oceanic crust (OC) at the core-mantle boundary and its ability to accumulate and form large thermochemical piles (such as the seismically observed Large Low Shear Velocity Provinces (LLSVPs)). Our high-resolution numerical simulations of thermochemical mantle convection suggest that the longevity of LLSVPs for up to three billion years, and possibly longer, can be ensured by a balance in the rate of segregation of high-density OC material to the core-mantle boundary (CMB) and the rate of its entrainment away from the CMB by mantle upwellings. For a range of parameters tested in this study, a large-scale compositional anomaly forms at the CMB, similar in shape and size to the LLSVPs. Neutrally buoyant thermochemical piles formed by mechanical stirringwhere thermally induced negative density anomaly is balanced by the presence of a fraction of dense anomalous materialbest resemble the geometry of LLSVPs. Such neutrally buoyant piles tend to emerge and survive for at least 3Gyr in simulations with quite different parameters. We conclude that for a plausible range of values of density anomaly of OC material in the lower mantleit is likely that it segregates to the CMB, gets mechanically mixed with the ambient material, and forms neutrally buoyant large-scale compositional anomalies similar in shape to the LLSVPs. KW - LLSVPs KW - thermochemical modeling KW - segregating oceanic crust KW - mantle convection Y1 - 2015 U6 - https://doi.org/10.1002/2014JB011688 SN - 2169-9313 SN - 2169-9356 VL - 120 IS - 5 SP - 3824 EP - 3847 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Bommer, Julian J. A1 - Coppersmith, Kevin J. A1 - Coppersmith, Ryan T. A1 - Hanson, Kathryn L. A1 - Mangongolo, Azangi A1 - Neveling, Johann A1 - Rathje, Ellen M. A1 - Rodriguez-Marek, Adrian A1 - Scherbaum, Frank A1 - Shelembe, Refilwe A1 - Stafford, Peter J. A1 - Strasser, Fleur O. T1 - A SSHAC Level 3 Probabilistic Seismic Hazard Analysis for a New-Build Nuclear Site in South Africa JF - Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute N2 - A probabilistic seismic hazard analysis has been conducted for a potential nuclear power plant site on the coast of South Africa, a country of low-to-moderate seismicity. The hazard study was conducted as a SSHAC Level 3 process, the first application of this approach outside North America. Extensive geological investigations identified five fault sources with a non-zero probability of being seismogenic. Five area sources were defined for distributed seismicity, the least active being the host zone for which the low recurrence rates for earthquakes were substantiated through investigations of historical seismicity. Empirical ground-motion prediction equations were adjusted to a horizon within the bedrock at the site using kappa values inferred from weak-motion analyses. These adjusted models were then scaled to create new equations capturing the range of epistemic uncertainty in this region with no strong motion recordings. Surface motions were obtained by convolving the bedrock motions with site amplification functions calculated using measured shear-wave velocity profiles. Y1 - 2015 U6 - https://doi.org/10.1193/060913EQS145M SN - 8755-2930 SN - 1944-8201 VL - 31 IS - 2 SP - 661 EP - 698 PB - Earthquake Engineering Research Institute CY - Oakland ER - TY - JOUR A1 - Reimold, Wolf Uwe A1 - Fischer, Luise A1 - Müller, Jan A1 - Kenkmann, Thomas A1 - Schmitt, Ralf-Thomas A1 - Altenberger, Uwe A1 - Kowitz, Astrid T1 - Impact-generated pseudotachylitic breccia in drill core BH-5 Hattberg, Siljan impact structure, Sweden JF - GFF N2 - Pseudotachylitic breccia (PTB) in the form of cm-wide melt breccia veinlets locally occurs on the exposed central uplift of the 380Ma Siljan impact structure. The host rock to the PTBs is the so-called Jarna granite of quartz monzonitic to syenodioritic composition. The nearly 603m long BH-5 drill core from Hattberg, near the centre of the Siljan central uplift, contains numerous veins and pods of PTB. In particular, two major zones of 60m combined width contain extensive PTB network breccias (30% actual melt breccia component), with individual melt breccia occurrences up to >1m in length. Core logging and petrographic and geochemical analysis of the core have been performed, and the data are interpreted to suggest the following. (1) The impact event caused low to moderate (at essentially <20GPa) shock deformation in the host rock and in clasts of this lithology within the PTB. (2) Macroscopic deformation of the basement mainly comprises fracturing, with only localised cataclasis. (3) No evidence for shock melting (i.e. compression/decompression melting early in the cratering process) could be observed. (4) Optical and scanning electron microscopy showed that dark PTB contains a definite melt component. (5) Shearing has significantly affected this part of the central uplift, but its effects are limited to very short displacements and likely did not result in extensive melting. (6) A frictional heating component upon melt generation can, however, not be excluded, as many PTB samples contain clasts of a mafic (gabbroic) component, although only in one place along the entire core, a 1.2cm-wide section through such material in direct contact to host rock was observed. Consequently, we suggest that, upon uplift in the central part of the impact structure, considerable melt volumes were generated locally, especially in areas that had been affected by extensive cataclasis and where grain size comminution favoured melt formation. Rapid decompression related to central uplift formation is the preferred process for the generation of the PTB melt breccias. Y1 - 2015 U6 - https://doi.org/10.1080/11035897.2015.1015264 SN - 1103-5897 SN - 2000-0863 VL - 137 IS - 2 SP - 141 EP - 162 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Dannberg, Juliane A1 - Sobolev, Stephan Vladimir T1 - Low-buoyancy thermochemical plumes resolve controversy of classical mantle plume concept JF - Nature Communications N2 - The Earth's biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models predict large plume heads that cause kilometre-scale surface uplift, and narrow (100 km radius) plume tails that remain in the mantle after the plume head spreads below the lithosphere. However, in many cases, such uplifts and narrow plume tails are not observed. Here using numerical models, we show that the issue can be resolved if major mantle plumes contain up to 15-20% of recycled oceanic crust in a form of dense eclogite, which drastically decreases their buoyancy and makes it depth dependent. We demonstrate that, despite their low buoyancy, large enough thermochemical plumes can rise through the whole mantle causing only negligible surface uplift. Their tails are bulky (4200 km radius) and remain in the upper mantle for 100 millions of years. Y1 - 2015 U6 - https://doi.org/10.1038/ncomms7960 SN - 2041-1723 VL - 6 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Huang, Wentao A1 - van Hinsbergen, Douwe J. J. A1 - Lippert, Peter C. A1 - Guo, Zhaojie A1 - Dupont-Nivet, Guillaume T1 - Paleomagnetic tests of tectonic reconstructions of the India-Asia collision zone JF - Geophysical research letters N2 - Several solutions have been proposed to explain the long-standing kinematic observation that postcollisional upper crustal shortening within the Himalaya and Asia is much less than the magnitude of India-Asia convergence. Here we implement these hypotheses in global plate reconstructions and test paleolatitudes predicted by the global apparent polar wander path against independent, and the most robust paleomagnetic data. Our tests demonstrate that (1) reconstructed 600-750km postcollisional intra-Asian shortening is a minimum value; (2) a 52Ma collision age is only consistent with paleomagnetic data if intra-Asian shortening was 900km; a 56-58Ma collision age requires greater intra-Asian shortening; (3) collision ages of 34 or 65Ma incorrectly predict Late Cretaceous and Paleogene paleolatitudes of the Tibetan Himalaya (TH); and (4) Cretaceous counterclockwise rotation of India cannot explain the paleolatitudinal divergence between the TH and India. All hypotheses, regardless of collision age, require major Cretaceous extension within Greater India. KW - India-Asia collision KW - tectonic reconstruction KW - paleomagnetism Y1 - 2015 U6 - https://doi.org/10.1002/2015GL063749 SN - 0094-8276 SN - 1944-8007 VL - 42 IS - 8 SP - 2642 EP - 2649 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Passarelli, Luigi A1 - Rivalta, Eleonora A1 - Cesca, Simone A1 - Aoki, Yosuke T1 - Stress changes, focal mechanisms, and earthquake scaling laws for the 2000 dike at Miyakejima (Japan) JF - Journal of geophysical research : Solid earth N2 - Faulting processes in volcanic areas result from a complex interaction of pressurized fluid-filled cracks and conduits with the host rock and local and regional tectonic setting. Often, volcanic seismicity is difficult to decipher in terms of the physical processes involved, and there is a need for models relating the mechanics of volcanic sources to observations. Here we use focal mechanism data of the energetic swarm induced by the 2000 dike intrusion at Miyakejima (Izu Archipelago, Japan), to study the relation between the 3-D dike-induced stresses and the characteristics of the seismicity. We perform a clustering analysis on the focal mechanism (FM) solutions and relate them to the dike stress field and to the scaling relationships of the earthquakes. We find that the strike and rake angles of the FMs are strongly correlated and cluster on bands in a strike-rake plot. We suggest that this is consistent with optimally oriented faults according to the expected pattern of Coulomb stress changes. We calculate the frequency-size distribution of the clustered sets finding that focal mechanisms with a large strike-slip component are consistent with the Gutenberg-Richter relation with a b value of about 1. Conversely, events with large normal faulting components deviate from the Gutenberg-Richter distribution with a marked roll-off on its right-hand tail, suggesting a lack of large-magnitude events (M-w>5.5). This may result from the interplay of the limited thickness and lower rock strength of the layer of rock above the dike, where normal faulting is expected, and lower stress levels linked to the faulting style and low confining pressure. KW - dike intrusion KW - dike-induced stresses KW - dike-induced seismicity KW - Miyakejima intrusion KW - Gutenberg-Richter relationship Y1 - 2015 U6 - https://doi.org/10.1002/2014JB011504 SN - 2169-9313 SN - 2169-9356 VL - 120 IS - 6 SP - 4130 EP - 4145 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Serno, Sascha A1 - Winckler, Gisela A1 - Anderson, Robert F. A1 - Maier, Edith A1 - Ren, Haojia A1 - Gersonde, Rainer A1 - Haug, Gerald H. T1 - Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool JF - Paleoceanography N2 - We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the Th-230-normalized He-4 flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745140years at 11,653year B.P., 680228years at 14,630year B.P., and 790498years at 23,290year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions. KW - Subarctic North Pacific KW - eolian dust KW - helium-4 KW - atmospheric circulation KW - chronostratigrapy KW - paleoreservoir age Y1 - 2015 U6 - https://doi.org/10.1002/2014PA002748 SN - 0883-8305 SN - 1944-9186 VL - 30 IS - 6 SP - 583 EP - 600 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Guillemoteau, Julien A1 - Tronicke, Jens T1 - Non-standard electromagnetic induction sensor configurations: Evaluating sensitivities and applicability JF - Journal of applied geophysics N2 - For near surface geophysical surveys, small-fixed offset loop-loop electromagnetic induction (EMI) sensors are usually placed parallel to the ground surface (i.e., both loops are at the same height above ground). In this study, we evaluate the potential of making measurements with a system that is not parallel to the ground; i.e., by positioning the system at different inclinations with respect to ground surface. First, we present the Maxwell theory for inclined magnetic dipoles over a homogeneous half space. By analyzing the sensitivities of such configurations, we,show that varying the angle of the system would result in improved imaging capabilities. For example, we show that acquiring data with a vertical system allows detection of a conductive body with a better lateral resolution compared to data acquired using standard horizontal configurations. The synthetic responses are presented for a heterogeneous medium and compared to field data acquired in the historical Park Sanssouci in Potsdam, Germany. After presenting a detailed sensitivity analysis and synthetic examples of such ground conductivity measurements, we suggest a new strategy of acquisition that allows to better estimate the true distribution of electrical conductivity using instruments with a fixed, small offset between the loops. This strategy is evaluated using field data collected at a well-constrained test-site in Horstwalde (Germany). Here, the target buried utility pipes are best imaged using vertical system configurations demonstrating the potential of our approach for typical applications. (C) 2015 Elsevier B.V. Pill rights reserved. KW - Electromagnetics KW - EMI sensors KW - Loop-loop systems KW - Near surface geophysics KW - Civil engineering KW - Sensitivity analysis Y1 - 2015 U6 - https://doi.org/10.1016/j.jappgeo.2015.04.008 SN - 0926-9851 SN - 1879-1859 VL - 118 SP - 15 EP - 23 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mishra, Praveen Kumar A1 - Anoop, Ambili A1 - Schettler, Georg A1 - Prasad, Sushma A1 - Jehangir, Arshid A1 - Menzel, Peter A1 - Naumann, Rudolf A1 - Yousuf, A. R. A1 - Basavaiah, Nathani A1 - Deenadayalan, Kannan A1 - Wiesner, Martin G. A1 - Gaye, Birgit T1 - Reconstructed late Quaternary hydrological changes from Lake Tso Moriri, NW Himalaya JF - Quaternary international : the journal of the International Union for Quaternary Research N2 - We present the results of our investigations on the radiocarbon dated core sediments from the Lake Tso Moriri, NW Himalaya aimed at reconstructing palaeohydrological changes in this climatically sensitive region. Based on the detailed geochemical, mineralogical and sedimentological analysis, we recognise several short-term fluctuations superimposed upon seven major palaeohydrological stages identified in this lake since similar to 26 cal ka. Stage I (>20.2 cal ka): shallow lake characterised by input of coarse-grained detrital sediments; Stage II (20.2-16.4 cal ka): lake deepening and intensification of this trend ca. 18 cal ka; Stage III (16.4-11.2 cal ka): rising lake levels with a short term wet phase (13.1-11.7 cal ka); Stage IV (11.2-8.5 cal ka): early Holocene hydrological maxima and highest lake levels inferred to have resulted from early Holocene Indian monsoon intensification, as records from central Asia indicate weaker westerlies during this interval; Stage V (8.5-5.5 cal ka): mid-Holocene climate deterioration; Stage VI (5.5-2.7 cal ka): progressive lowering of lake level; Stage VII (2.7-0 cal ka): onset of modern conditions. The reconstructed hydrological variability in Lake Tso Moriri is governed by temperature changes (meltwater inflow) and monsoon precipitation (increased runoff). A regional comparison shows considerable differences with other palaeorecords from peninsular India during late Holocene. (C) 2014 Elsevier Ltd and INQUA. All rights reserved. KW - Authigenic carbonates KW - Holocene KW - Indian summer monsoon KW - Lake sediments KW - Tso Moriri Lake KW - Westerlies Y1 - 2015 U6 - https://doi.org/10.1016/j.quaint.2014.11.040 SN - 1040-6182 SN - 1873-4553 VL - 371 SP - 76 EP - 86 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Riedel, Nils A1 - Stebich, Martina A1 - Anoop, Ambili A1 - Basavaiah, Nathani A1 - Menzel, Philip A1 - Prasad, Sushma A1 - Sachse, Dirk A1 - Sarkar, Saswati A1 - Wiesner, Martin T1 - Modern pollen vegetation relationships in a dry deciduous monsoon forest: A case study from Lonar Crater Lake, central India JF - Quaternary international : the journal of the International Union for Quaternary Research N2 - As part of ongoing research on Holocene lacustrine sediments of Lonar Crater Lake (central India), pollen assemblages in lake surface sediment and soil samples were studied to unravel pollenevegetation relationships, including pollen transport processes in tropical dry deciduous forest vegetation. Furthermore, palynological results were compared with geochemical proxies and spatial features of the lake sediments and the vegetation. The obtained data reveal strong differences in pollen assemblages and pollen concentrations between and within the studied trapping media. Local arboreal vegetation is adequately represented in the soil samples, but is less represented in the lake surface sediment samples. The composition of the lacustrine pollen assemblages is mainly influenced by patterns of transport through surface and channel runoff. Besides the relevance of our new data for reliable interpretation of fossil pollen spectra extracted from Lonar sediment cores, the results of this study are of general importance for the understanding of Quaternary pollen assemblages from tropical lacustrine archives, as well as for the implementation and selection of suitable approaches for quantitative pollen based environmental reconstructions in south Asia and beyond. (C) 2015 Elsevier Ltd and INQUA. All rights reserved. KW - Tropical dry deciduous forests KW - Modern pollen/vegetation relationships KW - Lonar Lake KW - Central India Y1 - 2015 U6 - https://doi.org/10.1016/j.quaint.2015.01.046 SN - 1040-6182 SN - 1873-4553 VL - 371 SP - 268 EP - 279 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Walter, Judith A1 - Lueck, Erika A1 - Bauriegel, Albrecht A1 - Richter, C. A1 - Zeitz, Jutta T1 - Multi-scale analysis of electrical conductivity of peatlands for the assessment of peat properties JF - European journal of soil science N2 - Peatlands store large amounts of carbon. This storage function has been reduced through intensive drainage, which leads to the decomposition of peat, resulting in a loss of carbon. Measurements of the real (sigma) and imaginary part (sigma) of electrical conductivity can deliver information on peat properties, such as the pore fluid conductivity (sigma(w)), cation exchange capacity (CEC), bulk density ((b)), water content (WC) and soil organic matter (SOM) content. These properties change with the peat's degree of decomposition (DD). To explore the relationships between the peat properties, sigma, sigma and DD, we focused on three different types of survey and scales. First, point measurements were made with a conductivity probe at various locations over a large area of northeast Germany to determine the degree of correlation between sigma and DD. Second, nine of these locations were selected for sampling to determine which of the properties sigma(w), CEC, (b), WC and SOM predominantly influence sigma and sigma. This multisite dataset includes the entire range of DD and was analysed in the laboratory. Third, one site was selected for a survey of sigma including sampling, to identify which properties mainly control sigma in a single-site approach. Statistical analysis revealed that for the multisite laboratory dataset, sigma(w) has the strongest effect on sigma, followed by CEC, whereas sigma is mainly determined by CEC. In a single-site approach, WC followed by CEC had a dominant effect on sigma. No clear correlation could be observed between (i) DD and peat properties and (ii) DD and sigma or sigma. This is because of the complex changes in properties with increasing DD. Y1 - 2015 U6 - https://doi.org/10.1111/ejss.12251 SN - 1351-0754 SN - 1365-2389 VL - 66 IS - 4 SP - 639 EP - 650 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Wesson, Robert L. A1 - Melnick, Daniel A1 - Cisternas, Marco A1 - Moreno, Marcos A1 - Ely, Lisa L. T1 - Vertical deformation through a complete seismic cycle at Isla Santa Maria, Chile JF - Nature geoscience N2 - Individual great earthquakes are posited to release the elastic strain energy that has accumulated over centuries by the gradual movement of tectonic plates(1,2). However, knowledge of plate deformation during a complete seismic cycle-two successive great earthquakes and the intervening interseismic period-remains incomplete(3). A complete seismic cycle began in south-central Chile in 1835 with an earthquake of about magnitude 8.5 (refs 4,5) and ended in 2010 with a magnitude 8.8 earthquake(6). During the first earthquake, an uplift of Isla Santa Maria by 2.4 to 3m was documented(4,5). In the second earthquake, the island was uplifted(7) by 1.8 m. Here we use nautical surveys made in 1804, after the earthquake in 1835 and in 1886, together with modern echo sounder surveys and GPS measurements made immediately before and after the 2010 earthquake, to quantify vertical deformation through the complete seismic cycle. We find that in the period between the two earthquakes, Isla Santa Maria subsided by about 1.4 m. We simulate the patterns of vertical deformation with a finite-element model and find that they agree broadly with predictions from elastic rebound theory(2). However, comparison with geomorphic and geologic records of millennial coastline emergence(8,9) reveal that 10-20% of the vertical uplift could be permanent. Y1 - 2015 U6 - https://doi.org/10.1038/NGEO2468 SN - 1752-0894 SN - 1752-0908 VL - 8 IS - 7 SP - 547 EP - U157 PB - Nature Publ. Group CY - New York ER - TY - JOUR A1 - Allroggen, Niklas A1 - van Schaik, N. Loes M. B. A1 - Tronicke, Jens T1 - 4D ground-penetrating radar during a plot scale dye tracer experiment JF - Journal of applied geophysics N2 - Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved. KW - Ground penetrating radar KW - Time-lapse imaging KW - Brilliant blue Y1 - 2015 U6 - https://doi.org/10.1016/j.jappgeo.2015.04.016 SN - 0926-9851 SN - 1879-1859 VL - 118 SP - 139 EP - 144 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Menzel, Philip A1 - Anupama, Krishnamurthy A1 - Basavaiah, Nathani A1 - Das, Brijraj Krishna A1 - Gaye, Birgit A1 - Herrmann, Nicole A1 - Prasad, Sushma T1 - The use of amino acid analyses in (palaeo-) limnological investigations: A comparative study of four Indian lakes in different climate regimes JF - Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society N2 - In the present study, we report the results of comprehensive amino acid (AA) analyses of four Indian lakes from different climate regimes. We focus on the investigation of sediment cores retrieved from the lakes but data of modern sediment as well as vascular plant, soil, and suspended particulate matter samples from individual lakes are also presented. Commonly used degradation and organic matter source indices are tested for their applicability to the lake sediments, and we discuss potential reasons for possible limitations. A principal component analysis including the monomeric AA composition of organic matter of all analysed samples indicates that differences in organic matter sources and the environmental properties of the individual lakes are responsible for the major variability in monomeric AA distribution of the different samples. However, the PCA also gives a factor that most probably separates the samples according to their state of organic matter degradation. Using the factor loadings of the individual AA monomers, we calculate a lake sediment degradation index (LI) that might be applicable to other palaeo-lake investigations. (C) 2015 Elsevier Ltd. All rights reserved. Y1 - 2015 U6 - https://doi.org/10.1016/j.gca.2015.03.028 SN - 0016-7037 SN - 1872-9533 VL - 160 SP - 25 EP - 37 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Allroggen, Niklas A1 - Tronicke, Jens A1 - Delock, Marcel A1 - Böniger, Urs T1 - Topographic migration of 2D and 3D ground-penetrating radar data considering variable velocities JF - Near surface geophysics N2 - We present a 2D/3D topographic migration scheme for ground-penetrating radar (GPR) data which is able to account for variable velocities by using the root mean square (rms) velocity approximation. We test our migration scheme using a synthetic 2D example and compare our migrated image to the results obtained using common GPR migration approaches. Furthermore, we apply it to 2D and 3D field data. These examples are recorded across common subsurface settings including surface topography and variations in the GPR subsurface velocity field caused by a shallow ground water table. In such field settings, our migration strategy provides well focused images of commonoffset GPR data without the need for a detailed interval velocity model. The synthetic and field examples demonstrate that our topographic migration scheme allows for accurate GPR imaging in the presence of variations in surface topography and subsurface velocity. Y1 - 2015 U6 - https://doi.org/10.3997/1873-0604.2014037 SN - 1569-4445 SN - 1873-0604 VL - 13 IS - 3 PB - European Association of Geoscientists & Engineers CY - Houten ER - TY - JOUR A1 - Tronicke, Jens A1 - Allroggen, Niklas T1 - Toward automated delineation of ground-penetrating radar facies in clastic sediments: An example from stratified glaciofluvial deposits JF - Geophysics N2 - Ground-penetrating radar (GPR) is an established geophysical method to explore near-surface sedimentary environments. Interpreting GPR images is largely based on manual procedures following concepts known as GPR facies analysis. We have developed a novel strategy to distinguish GPR facies in a largely automated and more objective manner. First, we calculate 13 textural attributes to quantify GPR reflection characteristics. Then, this database is reduced using principal component analysis. Finally, we image the dominating principal components using composite imaging and classify them using standard clustering methods. The potential of this work-flow is evaluated using a 2D GPR field example collected across stratified glaciofluvial deposits. Our results demonstrate that the derived facies images are well correlated with the composition and the porosity of the sediments as known from independent borehole logs. Our analysis strategy eases and improves the interpretability of GPR data and will help in a variety of geologic and hydrological problems. Y1 - 2015 U6 - https://doi.org/10.1190/GEO2015-0188.1 SN - 0016-8033 SN - 1942-2156 VL - 80 IS - 4 SP - A89 EP - A94 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - JOUR A1 - Teshebaeva, Kanayim A1 - Roessner, Sigrid A1 - Echtler, Helmut Peter A1 - Motagh, Mahdi A1 - Wetzel, Hans-Ulrich A1 - Molodbekov, Bolot T1 - ALOS/PALSAR InSAR Time-Series Analysis for Detecting Very Slow-Moving Landslides in Southern Kyrgyzstan JF - Remote sensing N2 - This study focuses on evaluating the potential of ALOS/PALSAR time-series data to analyze the activation of deep-seated landslides in the foothill zone of the high mountain Alai range in the southern Tien Shan (Kyrgyzstan). Most previous field-based landslide investigations have revealed that many landslides have indicators for ongoing slow movements in the form of migrating and newly developing cracks. L-band ALOS/PALSAR data for the period between 2007 and 2010 are available for the 484 km(2) area in this study. We analyzed these data using the Small Baseline Subset (SBAS) time-series technique to assess the surface deformation related to the activation of landslides. We observed up to +/- 17 mm/year of LOS velocity deformation rates, which were projected along the local steepest slope and resulted in velocity rates of up to -63 mm/year. The obtained rates indicate very slow movement of the deep-seated landslides during the observation time. We also compared these movements with precipitation and earthquake records. The results suggest that the deformation peaks correlate with rainfall in the 3 preceding months and with an earthquake event. Overall, the results of this study indicated the great potential of L-band InSAR time series analysis for efficient spatiotemporal identification and monitoring of slope activations in this region of high landslide activity in Southern Kyrgyzstan. Y1 - 2015 U6 - https://doi.org/10.3390/rs70708973 SN - 2072-4292 VL - 7 IS - 7 SP - 8973 EP - 8994 PB - MDPI CY - Basel ER - TY - JOUR A1 - Rodil, Iván F. A1 - Jaramillo, Eduardo A1 - Hubbard, David M. A1 - Dugan, Jenifer E. A1 - Melnick, Daniel A1 - Velasquez, Carlos T1 - Responses of Dune Plant Communities to Continental Uplift from a Major Earthquake: Sudden Releases from Coastal Squeeze JF - PLoS one N2 - Vegetated dunes are recognized as important natural barriers that shelter inland ecosystems and coastlines suffering daily erosive impacts of the sea and extreme events, such as tsunamis. However, societal responses to erosion and shoreline retreat often result in man-made coastal defence structures that cover part of the intertidal and upper shore zones causing coastal squeeze and habitat loss, especially for upper shore biota, such as dune plants. Coseismic uplift of up to 2.0 m on the Peninsula de Arauco (South central Chile, ca. 37.5 degrees S) caused by the 2010 Maule earthquake drastically modified the coastal landscape, including major increases in the width of uplifted beaches and the immediate conversion of mid to low sandy intertidal habitat to supralittoral sandy habitat above the reach of average tides and waves. To investigate the early stage responses in species richness, cover and across-shore distribution of the hitherto absent dune plants, we surveyed two formerly intertidal armoured sites and a nearby intertidal unarmoured site on a sandy beach located on the uplifted coast of Llico (Peninsula de Arauco) over two years. Almost 2 years after the 2010 earthquake, dune plants began to recruit, then rapidly grew and produced dune hummocks in the new upper beach habitats created by uplift at the three sites. Initial vegetation responses were very similar among sites. However, over the course of the study, the emerging vegetated dunes of the armoured sites suffered a slowdown in the development of the spatial distribution process, and remained impoverished in species richness and cover compared to the unarmoured site. Our results suggest that when released from the effects of coastal squeeze, vegetated dunes can recover without restoration actions. However, subsequent human activities and management of newly created beach and dune habitats can significantly alter the trajectory of vegetated dune development. Management that integrates the effects of natural and human induced disturbances, and promotes the development of dune vegetation as natural barriers can provide societal and conservation benefits in coastal ecosystems. Y1 - 2015 U6 - https://doi.org/10.1371/journal.pone.0124334 SN - 1932-6203 VL - 10 IS - 5 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Seifert, Linda I. A1 - Weithoff, Guntram A1 - Gaedke, Ursula A1 - Vos, Matthijs T1 - Warming-induced changes in predation, extinction and invasion in an ectotherm food web JF - Oecologia N2 - Climate change will alter the forces of predation and competition in temperate ectotherm food webs. This may increase local extinction rates, change the fate of invasions and impede species reintroductions into communities. Invasion success could be modulated by traits (e.g., defenses) and adaptations to climate. We studied how different temperatures affect the time until extinction of species, using bitrophic and tritrophic planktonic food webs to evaluate the relative importance of predatory overexploitation and competitive exclusion, at 15 and 25 A degrees C. In addition, we tested how inclusion of a subtropical as opposed to a temperate strain in this model food web affects times until extinction. Further, we studied the invasion success of the temperate rotifer Brachionus calyciflorus into the planktonic food web at 15 and 25 A degrees C on five consecutive introduction dates, during which the relative forces of predation and competition differed. A higher temperature dramatically shortened times until extinction of all herbivore species due to carnivorous overexploitation in tritrophic systems. Surprisingly, warming did not increase rates of competitive exclusion among the tested herbivore species in bitrophic communities. Including a subtropical herbivore strain reduced top-down control by the carnivore at high temperature. Invasion attempts of temperate B. calyciflorus into the food web always succeeded at 15 A degrees C, but consistently failed at 25 A degrees C due to voracious overexploitation by the carnivore. Pre-induction of defenses (spines) in B. calyciflorus before the invasion attempt did not change its invasion success at the high temperature. We conclude that high temperatures may promote local extinctions in temperate ectotherms and reduce their chances of successful recovery. KW - Community dynamics KW - Freshwater ecosystem KW - Global warming KW - Species range shift KW - Trophic interactions Y1 - 2015 U6 - https://doi.org/10.1007/s00442-014-3211-4 SN - 0029-8549 SN - 1432-1939 VL - 178 IS - 2 SP - 485 EP - 496 PB - Springer CY - New York ER - TY - JOUR A1 - Sauer, Daniela A1 - Stein, Christine A1 - Glatzel, Stephan A1 - Kühn, Jürgen A1 - Zarei, Mehdi A1 - Stahr, Karl T1 - Duricrusts in soils of the Alentejo (southern Portugal)-types, distribution, genesis and time of their formation JF - Journal of soils and sediments : protection, risk assessment and remediation N2 - This paper reports on extremely thick and massive duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of duricrust formation. After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. The duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. The thick duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of duricrust formation. KW - Duricrusts KW - Opal-A KW - Opal-CT KW - Palygorskite KW - Portugal KW - Silica Y1 - 2015 U6 - https://doi.org/10.1007/s11368-015-1066-x SN - 1439-0108 SN - 1614-7480 VL - 15 IS - 6 SP - 1437 EP - 1453 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Plunder, Alexis A1 - Agard, Philippe A1 - Chopin, Christian A1 - Pourteau, Amaury A1 - Okay, Aral I. T1 - Accretion, underplating and exhumation along a subduction interface: From subduction initiation to continental subduction (Tavsanli zone, W. Turkey) JF - Lithos : an international journal of mineralogy, petrology, and geochemistry N2 - We herein reappraise the pressure-temperature (PT) evolution of the high-pressure and low-temperature (HP-LT) Tavsanli zone (western Turkey) in order to (i) better characterize rock units exhumed along a cooling subduction interface, from birth to steady state and (ii) constrain exhumation and detachment dynamics, as well as mechanical coupling between plates. Based on PT estimates and field observations three oceanic complexes are recognized between the HP-LT continental margin and the obducted ophiolite, with PT estimates ranging from incipient metamorphism to blueschist-fades conditions. PT conditions for the continental unit are reappraised to 24 kbar and similar to 500 degrees C on the basis of pseudosection modelling and Raman spectroscopy on carbonaceous material. A tentative reconstruction of the subduction zone evolution is proposed using available radiometric and palaeogeographic data and recent thermomechanical modelling. Both PT conditions and field observations point out to the slicing of km-sized units at different preferred depths along the subduction interface, thus providing constraints on the dynamics of accretion and underplating. In particular, the comparison of PT estimates for the Tavsanli zone and for other broadly similar fossil subduction settings (i.e., Oman, Corsica, New Caledonia, Franciscan, Schistes Lustres) suggests that units are detached preferentially from the slab at specific depths of 30-40 km (i.e., downdip of the seismogenic zone) and similar to 80 km. We propose that these depths are controlled by major changes in mechanical coupling along the plate interface, whereas exhumation through time would rather be controlled by large-scale geodynamic boundary conditions. (C) 2015 Elsevier B.V. All rights reserved. KW - Subduction interface KW - PT estimates KW - HP-LT rocks KW - Accretion, underplating and exhumation processes Y1 - 2015 U6 - https://doi.org/10.1016/j.lithos.2015.01.007 SN - 0024-4937 SN - 1872-6143 VL - 226 SP - 233 EP - 254 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Brown, Maxwell C. A1 - Donadini, Fabio A1 - Nilsson, Andreas A1 - Panovska, Sanja A1 - Frank, Ute A1 - Korhonen, Kimmo A1 - Schuberth, Maximilian A1 - Korte, Monika A1 - Constable, Catherine G. T1 - GEOMAGIA50.v3: 2. A new paleomagnetic database for lake and marine sediments JF - Earth, planets and space N2 - Background: GEOMAGIA50.v3 for sediments is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data obtained from lake and marine sediments deposited over the past 50 ka. Its objective is to catalogue data that will improve our understanding of changes in the geomagnetic field, physical environments, and climate. Findings: GEOMAGIA50.v3 for sediments builds upon the structure of the pre-existing GEOMAGIA50 database for magnetic data from archeological and volcanic materials. A strong emphasis has been placed on the storage of geochronological data, and it is the first magnetic archive that includes comprehensive radiocarbon age data from sediments. The database will be updated as new sediment data become available. Conclusions: The web-based interface for the sediment database is located at http://geomagia.gfz-potsdam.de/geomagiav3/SDquery.php. This paper is a companion to Brown et al. (Earth Planets Space doi:10.1186/s40623-015-0232-0,2015) and describes the data types, structure, and functionality of the sediment database. KW - Geomagnetism KW - Paleomagnetism KW - Sediment magnetism KW - Rock magnetism KW - Environmental magnetism KW - Database KW - GEOMAGIA50 Y1 - 2015 U6 - https://doi.org/10.1186/s40623-015-0233-z SN - 1880-5981 VL - 67 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Reza, M. Toufiq A1 - Rottler, Erwin A1 - Tölle, Rainer A1 - Werner, Maja A1 - Ramm, Patrice A1 - Mumme, Jan T1 - Production, characterization, and biogas application of magnetic hydrochar from cellulose JF - Bioresource technology : biomass, bioenergy, biowastes, conversion technologies, biotransformation, production technologies N2 - Hydrothermal carbonization (HTC) produces carbon-rich nano-micro size particles. In this study, magnetic hydrochar (MHC) was prepared from model compound cellulose by simply adding ferrites during HTC. The effects of ferrites on HTC were evaluated by characterizing solid MHC and corresponding process liquid. Additionally, magnetic stability of MHC was tested by magnetic susceptibility method. Finally, MHC was used as support media for anaerobic films in anaerobic digestion (AD). Ash-free mass yield was around 50% less in MHC than hydrochar produced without ferrites at any certain HTC reaction condition, where organic part of MHC is mainly carbon. In fact, amorphous hydrochar was growing on the surface of inorganic ferrites. MHC maintained magnetic susceptibility regardless of reaction time at reaction temperature 250 degrees C. Pronounced inhibitory effects of magnetic hydrochar occurred during start-up of AD but diminished with prolong AD times. Visible biofilms were observed on the MHC by laser scanning microscope after AD. (C) 2015 Elsevier Ltd. All rights reserved. KW - Cellulose KW - Hydrothermal carbonization KW - Magnetic hydrochar KW - Magnetic susceptibility KW - Anaerobic digestion Y1 - 2015 U6 - https://doi.org/10.1016/j.biortech.2015.03.044 SN - 0960-8524 SN - 1873-2976 VL - 186 SP - 34 EP - 43 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kneis, David T1 - A lightweight framework for rapid development of object-based hydrological model engines JF - Environmental modelling & software with environment data news N2 - Computer-based simulation models are frequently used in hydrological research and engineering but also in other fields of environmental sciences. New case studies often require existing model concepts to be adapted. Extensions may be necessary due to the peculiarities of the studied natural system or subtleties of anthropogenic control. In other cases, simplifications must be made in response to scarce data, incomplete knowledge, or restrictions set by the spatio-temporal scale of application. This paper introduces an open-source modeling framework called ECHSE designed to cope with the above-mentioned challenges. It provides a lightweight infrastructure for the rapid development of new, reusable simulation tools and, more importantly, the safe modification of existing formulations. ECHSE-based models treat the simulated system as a collection of interacting objects. Although feedbacks are generally supported, the majority of the objects' interactions is expected to be of the feed-forward type. Therefore, the ECHSE software is particularly useful in the context of hydrological catchment modeling. Conversely, it is unsuitable, e.g., for fully hydrodynamic simulations and groundwater flow modeling. The focus of the paper is put on a comprehensible outline of the ECHSE's fundamental concepts and limitations. For the purpose of illustration, a specific, ECHSE-based solution for hydrological catchment modeling is presented which has undergone testing in a number of river basins. (C) 2015 Elsevier Ltd. All rights reserved. KW - Modeling framework KW - Genetic model KW - Hydrology KW - ECHSE Y1 - 2015 U6 - https://doi.org/10.1016/j.envsoft.2015.02.009 SN - 1364-8152 SN - 1873-6726 VL - 68 SP - 110 EP - 121 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kober, Florian A1 - Zeilinger, Gerold A1 - Hippe, Kristina A1 - Marc, Odin A1 - Lendzioch, Theodora A1 - Grischott, Reto A1 - Christl, Marcus A1 - Kubik, Peter W. A1 - Zola, Ramiro T1 - Tectonic and lithological controls on denudation rates in the central Bolivian Andes JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - The topographic signature of a mountain belt depends on the interplay of tectonic, climatic and erosional processes, whose relative importance changes over times, while quantifying these processes and their rates at specific times remains a challenge. The eastern Andes of central Bolivia offer a natural laboratory in which such interplay has been debated. Here, we investigate the Rio Grande catchment which crosses orthogonally the eastern Andes orogen from the Eastern Cordillera into the Subandean Zone, exhibiting a catchment relief of up to 5000 m. Despite an enhanced tectonic activity in the Subandes, local relief, mean and modal slopes and channel steepness indices are largely similar compared to the Eastern Cordillera and the intervening Interandean Zone. Nevertheless, a dataset of 57 new cosmogenic 10Be and 26AI catchment wide denudation rates from the Rio Grande catchment reveals up to one order of magnitude higher denudation rates in the Subandean Zone (mean 0.8 mm/yr) compared to the upstream physiographic regions. We infer that tectonic activity in the thrusting dominated Subandean belt causes higher denudation rates based on cumulative rock uplift investigations and due to the absence of a pronounced climate gradient. Furthermore, the lower rock strength of the Subandean sedimentary units correlates with mean slopes similar to the ones of the Eastern Cordillera and Interandean Zone, highlighting the fact, that lithology and rock strength can control high denudation rates at low slopes. Low denudation rates measured at the outlet of the Rio Grande catchment (Abapo) are interpreted to be a result of a biased cosmogenic nuclide mixing that is dominated by headwater signals from the Eastern Cordillera and the Interandean zone and limited catchment sediment connectivity in the lower river reaches. Therefore, comparisons of short- (i.e., sediment yield) and millennial denudation rates require caution when postulating tectonic and/or climatic forcing without detailed studies. (C) 2015 The Authors. Published by Elsevier B.V. KW - Rio Grande KW - seismicity KW - uplift KW - rock strength KW - cosmogenic nuclides KW - denudation Y1 - 2015 U6 - https://doi.org/10.1016/j.tecto.2015.06.037 SN - 0040-1951 SN - 1879-3266 VL - 657 SP - 230 EP - 244 PB - Elsevier CY - Amsterdam ER - TY - INPR A1 - Wang, Ping A1 - Scherler, Dirk A1 - Jing Liu-Zeng, A1 - Mey, Jürgen A1 - Avouac, Jean-Philippe A1 - Zhang, Yunda A1 - Shi, Dingguo T1 - GEOMORPHOLOGY Response to Comment on "Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet" T2 - Science N2 - In their Comment, Zeitler et al. do not challenge our results or interpretation. Our study does not disprove coupling between tectonic uplift and erosion but suggests that this coupling cannot be the sole explanation of rapid uplift in the Himalayan syntaxes. Y1 - 2015 SN - 0036-8075 SN - 1095-9203 VL - 349 IS - 6250 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Sarkar, Saswati A1 - Prasad, Sushma A1 - Wilkes, Heinz A1 - Riedel, Nils A1 - Stebich, Martina A1 - Basavaiah, Nathani A1 - Sachse, Dirk T1 - Monsoon source shifts during the drying mid-Holocene: Biomarker isotope based evidence from the core 'monsoon zone' (CMZ) of India JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - A better understanding of past variations of the Indian Summer Monsoon (ISM), that plays a vital role for the still largely agro-based economy in India, can lead to a better assessment of its potential impact under global climate change scenarios. However, our knowledge of spatiotemporal patterns of ISM strength is limited due to the lack of high-resolution, continental paleohydrological records. Here, we reconstruct centennial-scale hydrological variability during the Holocene associated to changes in the intensity of the ISM based on a record of lipid biomarker abundances and compound-specific stable isotopic composition of a 10 m long sediment core from saline alkaline Lonar Lake, situated in the core 'monsoon zone' of central India. We identified three main periods of distinct hydrology during the Holocene in central India. The period between 10.1 and 6 cal ka BP was likely the wettest during the Holocene. Lower average chain length (ACL) index values (29.4-28.6) and negative delta C-13(wax) values (-34.8 parts per thousand to -27.8 parts per thousand) of leaf wax n-alkanes indicate the dominance of woody C-3 vegetation in the catchment, and negative delta D-wax values (concentration weighted average) (-171 parts per thousand to -147 parts per thousand) suggest a wet period due to an intensified monsoon. After 6 cal ka BP, a gradual shift to less negative delta C-13(wax) values (particularly for the grass derived n-C-31) and appearance of the triterpene lipid tetrahymanol, generally considered as a marker for salinity and water column stratification, mark the onset of drier conditions. At 5.1 cal ka BP an increasing flux of leaf wax n-alkanes along with the highest flux of tetrahymanol indicate a major lowering of the lake level. Between 4.8 and 4 cal ka BP, we find evidence for a transition to arid conditions, indicated by high and strongly variable tetrahymanol flux. In addition, a pronounced shift to less negative delta C-13(wax) values, in particular for n-C-31 (-25.2 parts per thousand to -22.8 parts per thousand), during this period indicates a change of dominant vegetation to C-4 grasses. In agreement with other proxy data, such as deposition of evaporite minerals, we interpret this period to reflect the driest conditions in the region during the last 10.1 ka. This transition led to protracted late Holocene arid conditions after 4 ka with the presence of a permanent saline lake, supported by the sustained presence of tetrahymanol and more positive average delta D-wax values (-122 parts per thousand to -141 parts per thousand). A late Holocene peak of cyanobacterial biomarker input at 1.3 cal ka BP might represent an event of lake eutrophication, possibly due to human impact and the onset of cattle/livestock farming in the catchment. A unique feature of our record is the presence of a distinct transitional period between 4.8 and 4 cal ka BP, which was characterized by some of the most negative delta D-wax values during the Holocene (up to -180 parts per thousand), when all other proxy data indicate the driest conditions during the Holocene. These negative delta D-wax values can as such most reasonably be explained by a shift in moisture source area and/or pathways or rainfall seasonality during this transitional period. We hypothesize that orbital induced weakening of the summer solar insolation and associated reorganization of the general atmospheric circulation, as a possible southward displacement of the tropical rainbelt, led to an unstable hydroclimate in central India between 4.8 and 4 ka. KW - Indian Summer Monsoon KW - Holocene KW - Lonar Lake KW - Lipid biomarkers KW - Compound-specific stable isotopic KW - composition Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.06.020 SN - 0277-3791 VL - 123 SP - 144 EP - 157 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kühn, Nico M. A1 - Scherbaum, Frank T1 - Ground-motion prediction model building: a multilevel approach JF - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering N2 - A Bayesian ground-motion model is presented that directly estimates the coefficients of the model and the correlation between different ground-motion parameters of interest. The model is developed as a multi-level model with levels for earthquake, station and record terms. This separation allows to estimate residuals for each level and thus the estimation of the associated aleatory variability. In particular, the usually estimated within-event variability is split into a between-station and between-record variability. In addition, the covariance structure between different ground-motion parameters of interest is estimated for each level, i.e. directly the between-event, between-station and between-record correlation coefficients are available. All parameters of the model are estimated via Bayesian inference, which allows to assess their epistemic uncertainty in a principled way. The model is developed using a recently compiled European strong-motion database. The target variables are peak ground velocity, peak ground acceleration and spectral acceleration at eight oscillator periods. The model performs well with respect to its residuals, and is similar to other ground-motion models using the same underlying database. The correlation coefficients are similar to those estimated for other parts of the world, with nearby periods having a high correlation. The between-station, between-event and between-record correlations follow generally a similar trend. KW - Ground-motion prediction equation KW - Probabilistic seismic hazard analysis and Bayesian inference KW - Multilevel model KW - Correlation KW - Single-station sigma Y1 - 2015 U6 - https://doi.org/10.1007/s10518-015-9732-3 SN - 1570-761X SN - 1573-1456 VL - 13 IS - 9 SP - 2481 EP - 2491 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Wawrzenitz, Nicole A1 - Krohe, Alexander A1 - Baziotis, Ioannis A1 - Mposkos, Evripidis A1 - Kylander-Clark, Andrew R. C. A1 - Romer, Rolf L. T1 - LASS U-Th-Pb monazite and rutile geochronology of felsic high-pressure granulites (Rhodope, N Greece): Effects of fluid, deformation and metamorphic reactions in local subsystems JF - Lithos : an international journal of mineralogy, petrology, and geochemistry N2 - The specific chemical composition of monazite in shear zones is controlled by the syndeformation dissolution-precipitation reactions of the rock-forming minerals. This relation can be used for dating deformation, even when microfabric characteristics like shape preferred orientation or intracrystalline deformation of monazite itself are missing. Monazite contemporaneously formed in and around the shear zones may have different compositions. These depend on the local chemical context rather than reflecting successive crystallization episodes of monazite. This is demonstrated in polymetamorphic, mylonitic high-pressure (HP) garnet-kyanite granulites of the Alpine Sidironero Complex (Rhodope UHP terrain, Northern Greece). The studied mylonitic rocks escaped from regional migmatization at 40-36 Ma and from subsequent shearing through cooling until 36 Ma. In-situ laser-ablation split-stream inductively-coupled plasma mass spectrometry (LASS) analyses have been carried out on monazite from micro-scale shear zones, from pre-mylonitic microlithons as well as of monazite inclusions in relictic minerals complimented by U-Pb data on rutile and Rb-Sr data of biotite. Two major metamorphic episodes, Mesozoic and Cenozoic, are constrained. Chemical compositions, isotopic characteristics and apparent ages systematically vary among monazite of four different microfabric domains (I-IV). Within three pre-mylonitic domains (inclusions in (I) pre-mylonitic kyanite and (II) garnet porphyroclasts, and (III) in pre-mylonitic microlithons) monazite yields ages of ca. 130-150 Ma for HP-granulite metamorphism, in line with previous geochronological results in the area. Patchy alteration of the pre-mylonitic monazite by intra-grain dissolution-precipitation processes variably increased negative Eu anomaly and reduced the HREE contents. The apparent age of this altered monazite is reduced. Monazite in the syn-mylonitic shear bands (IV) differs in chemical composition from unaltered and altered monazite of the three pre-mylonitic domains by having a significantly more pronounced negative Eu anomaly, a flatter HREE pattern, and high Th content. These compositional characteristics are linked with syn-mylonitic formation of plagioclase and resorption of garnet in the shear bands under amphibolite fades conditions. The absence of pre-mylonitic monazite in the shear zones, in contrast to the other domains, suggests complete dissolution of old and formation of new monazite. This probably results from an increased alkalinity and reactivity of the fluid that again is controlled by syn-mylonitic interaction with feldspar and apatite in the shear zones. There, the deformation was accommodated by dissolution precipitation creep at ca. 690 +/- 50 degrees C and 6-7.5 kbar. Growth of monazite at 55 +/- 1 Ma dates this deformation, which precedes the regional migmatization of the Sidironero Complex, whereas rutile and biotite ages reflect these later stages. This new pressure-temperature-time constraint for a relictic deformation structure provides insight into the still missing parts of the overall metamorphic, deformation and exhumation processes of the UHP units in the Rhodope. (C) 2015 Elsevier B.V. All rights reserved. KW - In-situ Laser Ablation Split Stream ICPMS KW - UHP exhumation KW - Dissolution precipitation replacement KW - Creep KW - HP-granulite KW - Fluid-rock interaction Y1 - 2015 U6 - https://doi.org/10.1016/j.lithos.2015.06.029 SN - 0024-4937 SN - 1872-6143 VL - 232 SP - 266 EP - 285 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mischke, Steffen A1 - Opitz, Stephan A1 - Kalbe, Johannes A1 - Ginat, Hanan A1 - Al-Saqarat, Bety T1 - Palaeoenvironmental inferences from late Quaternary sediments of the Al Jafr Basin, Jordan JF - Quaternary international : the journal of the International Union for Quaternary Research N2 - Sedimentological, palaeontological and mineralogical analyses of sediments from the endorheic Al Jafr Basin were conducted to better understand the depositional and hydrological conditions on the southern Jordan Plateau in the late Quaternary. Surficially exposed carbonate-rich sediments in the western part of the basin contain ostracod (micro-crustacean) shells of Ilyocypris cf. bradyi, Candona neglecta, Heterocypris salina, Fabaeformiscandona fabaeformis, Pseudocandona sp. and Herpetocypris brevicaudata. The shells of these and other more rare species, and charophyte and mollusc remains indicate that the sediments were formed in a wetland setting of shallow freshwater to slightly oligohaline ponds, streams and swamps. The present more northern distribution of some of the recorded taxa implies that climate conditions were probably cooler during the wetland formation. Radiocarbon age data for biogenic carbonate from two locations suggest that the wetland setting existed during the second half of Marine Isotope Stage (MIS) 3 or possibly earlier. A significantly higher water table must have existed in the basin during wetland formation; and wetter climate conditions are inferred for the catchment or at least for its highest and most humid westernmost part. Deflation and local sediment accumulation by wind and occasional sheet-wash events apparently prevailed in the region since MIS 2. Our newly presented data and inferences do not support the reconstruction of a previously reported large and relatively deep Pleistocene lake in the Al Jafr Basin. However, more extensive studies are certainly required for a detailed assessment of the Quaternary hydrological conditions in southern Jordan. (C) 2014 Elsevier Ltd and INQUA. All rights reserved. KW - Wetlands KW - Ostracoda KW - Marine Isotope Stage 3 KW - Late Pleistocene KW - Eastern Mediterranean KW - Southern Levant Y1 - 2015 U6 - https://doi.org/10.1016/j.quaint.2014.12.041 SN - 1040-6182 SN - 1873-4553 VL - 382 SP - 154 EP - 167 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Hunke, Philip A1 - Müller, Eva Nora A1 - Schröder-Esselbach, Boris A1 - Zeilhofer, Peter T1 - The Brazilian Cerrado: assessment of water and soil degradation in catchments under intensive agricultural use JF - Ecohydrology : ecosystems, land and water process interactions, ecohydrogeomorphology N2 - The Brazilian Cerrado is recognized as one of the most threatened biomes in the world, as the region has experienced a striking change from natural Cerrado vegetation to intense cash crop production. This paper reviews the history of land conversion in the Cerrado and the development of soil properties and water resources under past and ongoing land use. We compared soil and water quality parameters from different land uses considering 80 soil and 18 water studies conducted in different regions across the Cerrado to provide quantitative evidence of soil and water alterations from land use change. Following the conversion of native Cerrado, significant effects on soil pH, bulk density and available P and K for croplands and less-pronounced effects on pastures were evident. Soil total N did not differ between land uses because most of the sites classified as croplands were nitrogen-fixing soybeans, which are not artificially fertilized with N. In contrast, water quality studies showed nitrogen enrichment in agricultural catchments, indicating fertilizer impacts and potential susceptibility to eutrophication. Regardless of the land use, P is widely absent because of the high-fixing capacities of deeply weathered soils and the filtering capacity of riparian vegetation. Pesticides, however, were consistently detected throughout the entire aquatic system. In several case studies, extremely high-peak concentrations exceeded Brazilian and European Union (EU) water quality limits, which were potentially accompanied by serious health implications. Land use intensification is likely to continue, particularly in regions where less annual rainfall and severe droughts are projected in the northeastern and western Cerrado. Thus, the leaching risk and displacement of agrochemicals are expected to increase, particularly because the current legislation has caused a reduction in riparian vegetation. We conclude that land use intensification is likely to seriously limit the Cerrado's future regarding both agricultural productivity and ecosystem stability. Because only limited data are available, we recommend further field studies to understand the interaction between terrestrial and aquatic systems. This study may serve as a valuable database for integrated modelling to investigate the impact of land use and climate change on soil and water resources and to test and develop mitigation measures for the Cerrado. Copyright (C) 2014 John Wiley & Sons, Ltd. KW - Cerrado KW - land degradation KW - ecosystem change KW - water quality KW - soil parameters KW - ecohydrology KW - land use change KW - Mato Grosso KW - pesticides KW - cash crops Y1 - 2015 U6 - https://doi.org/10.1002/eco.1573 SN - 1936-0584 SN - 1936-0592 VL - 8 IS - 6 SP - 1154 EP - 1180 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Ren, Haojia A1 - Studer, Anja S. A1 - Serno, Sascha A1 - Sigman, Daniel M. A1 - Winckler, Gisela A1 - Anderson, Robert F. A1 - Oleynik, Sergey A1 - Gersonde, Rainer A1 - Haug, Gerald H. T1 - Glacial-to-interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels JF - Paleoceanography N2 - Reduced nitrate supply to the subarctic North Pacific (SNP) surface during the last ice age has been inferred from coupled changes in diatom-bound delta N-15 (DB-delta N-15), bulk sedimentary delta N-15, and biogenic fluxes. However, the reliability of bulk sedimentary and DB-delta N-15 has been questioned, and a previously reported delta N-15 minimum during Heinrich Stadial 1 (HS1) has proven difficult to explain. In a core from the western SNP, we report the foraminifera-bound delta N-15 (FB-delta N-15) in Neogloboquadrina pachyderma and Globigerina bulloides, comparing them with DB-delta N-15 in the same core over the past 25 kyr. The delta N-15 of all recorders is higher during the Last Glacial Maximum (LGM) than in the Holocene, indicating more complete nitrate consumption. N. pachyderma FB-delta N-15 is similar to DB-delta N-15 in the Holocene but 2.2% higher during the LGM. This difference suggests a greater sensitivity of FB-delta(15)NZ to changes in summertime nitrate drawdown and delta N-15 rise, consistent with a lag of the foraminifera relative to diatoms in reaching their summertime production peak in this highly seasonal environment. Unlike DB-delta N-15, FB-delta N-15 does not decrease from the LGM into HS1, which supports a previous suggestion that the HS1 DB-delta N-15 minimum is due to contamination by sponge spicules. FB-delta N-15 drops in the latter half of the Bolling/Allerod warm period and rises briefly in the Younger Dryas cold period, followed by a decline into the mid-Holocene. The FB-delta N-15 records suggest that the coupling among cold climate, reduced nitrate supply, and more complete nitrate consumption that characterized the LGM also applied to the deglacial cold events. Y1 - 2015 U6 - https://doi.org/10.1002/2014PA002765 SN - 0883-8305 SN - 1944-9186 VL - 30 IS - 9 SP - 1217 EP - 1232 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Fahle, Marcus A1 - Hohenbrink, Tobias Ludwig A1 - Dietrich, Ottfried A1 - Lischeid, Gunnar T1 - Temporal variability of the optimal monitoring setup assessed using information theory JF - Water resources research N2 - Hydrology is rich in methods that use information theory to evaluate monitoring networks. Yet in most existing studies, only the available data set as a whole is used, which neglects the intraannual variability of the hydrological system. In this paper, we demonstrate how this variability can be considered by extending monitoring evaluation to subsets of the available data. Therefore, we separately evaluated time windows of fixed length, which were shifted through the data set, and successively extended time windows. We used basic information theory measures and a greedy ranking algorithm based on the criterion of maximum information/minimum redundancy. The network investigated monitored surface and groundwater levels at quarter-hourly intervals and was located at an artificially drained lowland site in the Spreewald region in north-east Germany. The results revealed that some of the monitoring stations were of value permanently while others were needed only temporally. The prevailing meteorological conditions, particularly the amount of precipitation, affected the degree of similarity between the water levels measured. The hydrological system tended to act more individually during periods of no or little rainfall. The optimal monitoring setup, its stability, and the monitoring effort necessary were influenced by the meteorological forcing. Altogether, the methodology presented can help achieve a monitoring network design that has a more even performance or covers the conditions of interest (e.g., floods or droughts) best. KW - artificially drained lowland KW - surface water levels KW - hydrometric network design KW - Shannon entropy KW - shallow groundwater tables Y1 - 2015 U6 - https://doi.org/10.1002/2015WR017137 SN - 0043-1397 SN - 1944-7973 VL - 51 IS - 9 SP - 7723 EP - 7743 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Behrens, Ricarda A1 - Bouchez, Julien A1 - Schuessler, Jan A. A1 - Dultz, Stefan A1 - Hewawasam, Tilak A1 - von Blanckenburg, Friedhelm T1 - Mineralogical transformations set slow weathering rates in low-porosity metamorphic bedrock on mountain slopes in a tropical climate JF - Chemical geology : official journal of the European Association for Geochemistry N2 - In the Sri Lankan Highlands erosion and chemical weathering rates are among the lowest for global mountain denudation. In this tropical humid setting, highly weathered deep saprolite profiles have developed from high-grade metamorphic charnockite during spheroidal weathering of the bedrock. The spheroidal weathering produces rounded corestones and spalled rindlets at the rock-saprolite interface. We used detailed textural, mineralogical and chemical analyses to reconstruct the sequence of weathering reactions and their causes. The first mineral attacked by weathering was found to be pyroxene initiated by in situ Fe oxidation. Volumetric calculations suggest that this oxidation leads to the generation of porosity due to the formation of micro-fractures allowing for fluid transport and subsequent dissolution of biotite and plagioclase. The rapid ensuing plagioclase weathering leads to formation of high secondary porosity in the corestone over a distance of only a few cm and eventually to the final disaggregation of bedrock to saprolite. The first secondary phases are oxides or amorphous precipitates from which secondary minerals (mainly gibbsite, kaolinite and goethite) form. As oxidation is the first weathering reaction, the supply of O-2 is a rate-limiting factor for chemical weathering. Hence, the supply of O-2 and its consumption at depth connects processes at the weathering front with those at the Earth's surface in a feedback mechanism. The strength of the feedback depends on the relative weight of advective versus diffusive transport of O-2 through the weathering profile. The feedback will be stronger with dominating diffusive transport. The low weathering rate is explained by the nature of this feedback that is ultimately dependent on the transport of O-2 through the whole regolith, and on lithological factors such as low bedrock porosity and the amount of Fe-bearing primary minerals. Tectonic quiescence in this region and low pre-development erosion rate (attributed to a dense vegetation cover) minimize the rejuvenation of the thick and cohesive regolith column, finally leading to low denudation rates. (C) 2015 Elsevier B.V. All rights reserved. KW - Weathering KW - Critical zone KW - Corestone KW - Regolith KW - Sri Lanka Y1 - 2015 U6 - https://doi.org/10.1016/j.chemgeo.2015.07.008 SN - 0009-2541 SN - 1878-5999 VL - 411 SP - 283 EP - 298 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kallmeyer, Jens A1 - Grewe, Sina A1 - Glombitza, Clemens A1 - Kitte, J. Axel T1 - Microbial abundance in lacustrine sediments: a case study from Lake Van, Turkey JF - International journal of earth sciences N2 - The ICDP "PaleoVan" drilling campaign at Lake Van, Turkey, provided a long (> 100 m) record of lacustrine subsurface sedimentary microbial cell abundance. After the ICDP campaign at Potrok Aike, Argentina, this is only the second time deep lacustrine cell counts have been documented. Two sites were cored and revealed a strikingly similar cell distribution despite differences in organic matter content and microbial activity. Although shifted towards higher values, cell counts from Lake Potrok Aike, Argentina, reveal very similar distribution patterns with depth. The lacustrine cell count data are significantly different from published marine records; the most probable cause is differences in sedimentary organic matter composition with marine sediments containing a higher fraction of labile organic matter. Previous studies showed that microbial activity and abundance increase centimetres to metres around geologic interfaces. The finely laminated Lake Van sediment allowed studying this phenomenon on the microscale. We sampled at the scale of individual laminae, and in some depth intervals, we found large differences in microbial abundance between the different laminae. This small-scale heterogeneity is normally overlooked due to much larger sampling intervals that integrate over several centimetres. However, not all laminated intervals exhibit such large differences in microbial abundance, and some non-laminated horizons show large variability on the millimetre scale as well. The reasons for such contrasting observations remain elusive, but indicate that heterogeneity of microbial abundance in subsurface sediments has not been taken into account sufficiently. These findings have implications not just for microbiological studies but for geochemistry as well, as the large differences in microbial abundance clearly show that there are distinct microhabitats that deviate considerably from the surrounding layers. KW - Subsurface biosphere KW - Deep biosphere KW - Lake Van KW - Cell counts KW - Lacustrine sediment Y1 - 2015 U6 - https://doi.org/10.1007/s00531-015-1219-6 SN - 1437-3254 SN - 1437-3262 VL - 104 IS - 6 SP - 1667 EP - 1677 PB - Springer CY - New York ER - TY - JOUR A1 - Rumpf, Michael A1 - Tronicke, Jens T1 - Assessing uncertainty in refraction seismic traveltime inversion using a global inversion strategy JF - Geophysical prospecting N2 - To analyse and invert refraction seismic travel time data, different approaches and techniques have been proposed. One common approach is to invert first-break travel times employing local optimization approaches. However, these approaches result in a single velocity model, and it is difficult to assess the quality and to quantify uncertainties and non-uniqueness of the found solution. To address these problems, we propose an inversion strategy relying on a global optimization approach known as particle swarm optimization. With this approach we generate an ensemble of acceptable velocity models, i.e., models explaining our data equally well. We test and evaluate our approach using synthetic seismic travel times and field data collected across a creeping hillslope in the Austrian Alps. Our synthetic study mimics a layered near-surface environment, including a sharp velocity increase with depth and complex refractor topography. Analysing the generated ensemble of acceptable solutions using different statistical measures demonstrates that our inversion strategy is able to reconstruct the input velocity model, including reasonable, quantitative estimates of uncertainty. Our field data set is inverted, employing the same strategy, and we further compare our results with the velocity model obtained by a standard local optimization approach and the information from a nearby borehole. This comparison shows that both inversion strategies result in geologically reasonable models (in agreement with the borehole information). However, analysing the model variability of the ensemble generated using our global approach indicates that the result of the local optimization approach is part of this model ensemble. Our results show the benefit of employing a global inversion strategy to generate near-surface velocity models from refraction seismic data sets, especially in cases where no detailed a priori information regarding subsurface structures and velocity variations is available. KW - Inversion KW - Seismic refraction KW - Uncertainty Y1 - 2015 U6 - https://doi.org/10.1111/1365-2478.12240 SN - 0016-8025 SN - 1365-2478 VL - 63 IS - 5 SP - 1188 EP - 1197 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Ghods, Abdolreza A1 - Shabanian, Esmaeil A1 - Bergman, Eric A1 - Faridi, Mohammad A1 - Donner, Stefanie A1 - Mortezanejad, Gholamreza A1 - Aziz-Zanjani, Asiyeh T1 - The Varzaghan-Ahar, Iran, Earthquake Doublet (M-w 6.4, 6.2): implications for the geodynamics of northwest Iran JF - Geophysical journal international N2 - On 2012 August 11, a pair of large, damaging earthquakes struck the Varzaghan-Ahar region in northwest Iran, in a region where there was no major mapped fault or any well-documented historical seismicity. To investigate the active tectonics of the source region we applied a combination of seismological methods (local aftershock network, calibrated multiple event relocation and focal mechanism studies), field observations (structural geology and geomorphological) and inversions for the regional stress field. The epicentral region is north of the North Tabriz Fault. The first main shock is characterized by right-lateral strike-slip motion on an almost E-W fault plane of about 23 km length extending from the surface to a depth of about 14 km. The second main shock occurred on an ENE-striking fault that dips at 60-70A degrees to the NW. Independent inversions of focal mechanisms and geologically determined fault kinematic data for the active stress state yield a transpressional tectonic regime with sigma(1) oriented N132E. For the region northeast of the North Tabriz Fault, the presence of rigid lithosphere of the South Caspian Basin implies the kinematic adjustment by northward transferring of the contracted masses through both distributed deformation and structural deflections. Our results suggest that the kinematic adjustment inside a contracting wedge may occur along interacting crosswise or conjugate faults to accommodate low rates of internal deformation. At a global scale, our results indicate that despite the basic assumption of 'rigid blocks' in geodetic plate modelling, internal deformation of block-like regions could control the kinematics of deformation and the level of seismic hazard within and around such regions of low deformation rate. KW - Earthquake source observations KW - Seismicity and tectonics KW - Continental neotectonics KW - Continental tectonics: compressional KW - Dynamics: seismotectonics KW - Asia Y1 - 2015 U6 - https://doi.org/10.1093/gji/ggv306 SN - 0956-540X SN - 1365-246X VL - 203 IS - 1 SP - 522 EP - 540 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Knudsen, Mads Faurschou A1 - Egholm, David L. A1 - Jacobsen, Bo Holm A1 - Larsen, Nicolaj Krog A1 - Jansen, John D. A1 - Andersen, Jane Lund A1 - Linge, Henriette C. T1 - A multi-nuclide approach to constrain landscape evolution and past erosion rates in previously glaciated terrains JF - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques N2 - Cosmogenic nuclides are typically used to either constrain an exposure age, a burial age, or an erosion rate. Constraining the landscape history and past erosion rates in previously glaciated terrains is, however, notoriously difficult because it involves a large number of unknowns. The potential use of cosmogenic nuclides in landscapes with a complex history of exposure and erosion is therefore often quite limited. Here, we present a novel multi-nuclide approach to study the landscape evolution and past erosion rates in terrains with a complex exposure history, particularly focusing on regions that were repeatedly covered by glaciers or ice sheets during the Quaternary. The approach, based on the Markov Chain Monte Carlo (MCMC) technique, focuses on mapping the range of landscape histories that are consistent with a given set of measured cosmogenic nuclide concentrations. A fundamental assumption of the model approach is that the exposure history at the site/location can be divided into two distinct regimes: i) interglacial periods characterized by zero shielding due to overlying ice and a uniform interglacial erosion rate, and ii) glacial periods characterized by 100% shielding and a uniform glacial erosion rate. We incorporate the exposure history in the model framework by applying a threshold value to the global marine benthic delta O-18 record and include the threshold value as a free model parameter, hereby taking into account global changes in climate. However, any available information on the glacial-interglacial history at the sampling location, in particular the timing of the last deglaciation event, is readily incorporated in the model to constrain the inverse problem. Based on the MCMC technique, the model delineates the most likely exposure history, including the glacial and interglacial erosion rates, which, in turn, makes it possible to reconstruct an exhumation history at the site. We apply the model to two landscape scenarios based on synthetic data and two landscape scenarios based on paired Be-10/Al-26 data from West Greenland, which makes it possible to quantify the denudation rate at these locations. The model framework, which currently incorporates any combination of the following nuclides Be-10, Al-26, C-14, and Ne-21, is highly flexible and can be adapted to many different landscape settings. The model framework may also be used in combination with physics-based landscape evolution models to predict nuclide concentrations at different locations in the landscape. This may help validate the landscape models via comparison to measured nuclide concentrations or to devise new effective sampling strategies. (C) 2015 The Authors. Published by Elsevier B.V. KW - Cosmogenic-nuclide geochronology KW - Markov Chain Monte Carlo inversion KW - Glacial landscape history KW - Erosion rate reconstructions KW - Quaternary climate Y1 - 2015 U6 - https://doi.org/10.1016/j.quageo.2015.08.004 SN - 1871-1014 SN - 1878-0350 VL - 30 SP - 100 EP - 113 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Wiesmeier, Martin A1 - Munro, Sam A1 - Barthold, Frauke Katrin A1 - Steffens, Markus A1 - Schad, Peter A1 - Kögel-Knabner, Ingrid T1 - Carbon storage capacity of semi-arid grassland soils and sequestration potentials in northern China JF - Global change biology N2 - Organic carbon (OC) sequestration in degraded semi-arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon (SOC) sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the OC storage capacity of semi-arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum OC saturation of silt and clay particles <20m, OC sequestration potentials of degraded steppe soils (grazing land, arable land, eroded areas) were estimated. The analysis of natural grassland soils revealed a strong linear regression between the proportion of the fine fraction and its OC content, confirming the importance of silt and clay particles for OC stabilization in steppe soils. This relationship was similar to derived regressions in temperate and tropical soils but on a lower level, probably due to a lower C input and different clay mineralogy. In relation to the estimated OC storage capacity, degraded steppe soils showed a high OC saturation of 78-85% despite massive SOC losses due to unsustainable land use. As a result, the potential of degraded grassland soils to sequester additional OC was generally low. This can be related to a relatively high contribution of labile SOC, which is preferentially lost in the course of soil degradation. Moreover, wind erosion leads to substantial loss of silt and clay particles and consequently results in a direct loss of the ability to stabilize additional OC. Our findings indicate that the SOC loss in semi-arid environments induced by intensive land use is largely irreversible. Observed SOC increases after improved land management mainly result in an accumulation of labile SOC prone to land use/climate changes and therefore cannot be regarded as contribution to long-term OC sequestration. KW - climate change KW - fine fraction KW - soil organic carbon KW - soil texture KW - steppe soils Y1 - 2015 U6 - https://doi.org/10.1111/gcb.12957 SN - 1354-1013 SN - 1365-2486 VL - 21 IS - 10 SP - 3836 EP - 3845 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Ebert, Thomas A1 - Trauth, Martin H. T1 - Semi-automated detection of annual laminae (varves) in lake sediments using a fuzzy logic algorithm JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Annual laminae (varves) in lake sediments are typically visually identified, measured and counted, although numerous attempts have been made to automate this process. The reason for the failure of most of these automated algorithms for varve counting is the complexity of the seasonal laminations, typically rich in lateral fades variations and internal heterogeneities. In the manual counting of varves, the investigator acquired and interpreted flexible numbers of complex decision criteria to understand whether a particular simple lamination is a varve or not. Fuzzy systems simulate the flexible decision making process in a computer by introducing a smooth transition between true varve and false varve. In our investigation, we use an adaptive neuro fuzzy inference system (ANFIS) to detect varves on the basis of a digital image of the sediment. The results of the application of the ANFIS to laminated sediments from the Meerfelder Maar (Eifel, Germany) and from a landslide-dammed lake in the Quebrada de Cafayate of Argentina are compared with manual varve counts and possible reasons for the differences are discussed. (C) 2015 Elsevier B.V. All rights reserved. KW - Varve KW - Lake sediment KW - Image processing KW - Fuzzy logic KW - MATLAB KW - Statistics Y1 - 2015 U6 - https://doi.org/10.1016/j.palaeo.2015.05.024 SN - 0031-0182 SN - 1872-616X VL - 435 SP - 272 EP - 282 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jenny, Bernhard A1 - Buddeberg, Jonas A1 - Hoarau, Charlotte A1 - Liem, Johannes T1 - Plan oblique relief for web maps JF - Cartography and geographic information science N2 - Plan oblique relief shows terrain with a side view on a two-dimensional map, resulting in visualizations where the third dimension of the terrain is more explicit than on traditional two-dimensional maps. Existing plan oblique maps are static: the angle of terrain inclination is not adjustable and the orientation of plan oblique inclination does not change with the orientation of the map. This article introduces two complementary methods that address these issues by using the 3D graphics pipeline to render plan oblique relief for tile-based web maps. The goal is to allow users to adjust the terrain inclination and map rotation angles to better visualize the third dimension of the terrain. The first method pre-renders plan oblique tiles with a server-side application. The tiles are visualized with a standard web mapping framework. The second method renders plan oblique relief on-the-fly in a web browser using WebGL and a customized version of OpenLayers 3, which enables users to select arbitrary terrain inclination and map rotation angles. The second method uses a tiled digital terrain model that is loaded by the web browser. The browser applies the plan oblique transformation, computes a shaded relief, and texturizes the terrain with tiled map layers. KW - plan oblique relief KW - 3D map KW - relief map KW - terrain map KW - WebGL KW - OpenLayers 3 Y1 - 2015 U6 - https://doi.org/10.1080/15230406.2015.1015169 SN - 1523-0406 SN - 1545-0465 VL - 42 IS - 5 SP - 410 EP - 418 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Selle, Benny A1 - Lange, Holger A1 - Lischeid, Gunnar A1 - Hauhs, Michael T1 - Transit times of water under steady stormflow conditions in the Gardsjon G1 catchment JF - Hydrological processes N2 - In this paper we report on a series of replicated tracer experiments with deuterium conducted under controlled, steady stormflow conditions at the Gardsjon G1 catchment in south-western Sweden. In five different years, these experiments were carried out in a subcatchment of G1. Deuterium was applied as a narrow pulse so that distributions of water transit times could be directly inferred from the observed tracer breakthrough curves. Significantly different transit times of water were observed under similar experimental conditions. Coefficients of variation for estimated mean transit times were greater than 60%, which can be understood as a measure of the interannual variability for this type of experiments. Implications for water transit times under more natural flow conditions as wells as for future experimentation are discussed. Copyright (c) 2015 John Wiley & Sons, Ltd. KW - travel time distribution KW - groundwater age KW - connectivity Y1 - 2015 U6 - https://doi.org/10.1002/hyp.10528 SN - 0885-6087 SN - 1099-1085 VL - 29 IS - 22 SP - 4657 EP - 4665 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Lehmann, Jascha A1 - Coumou, Dim A1 - Frieler, Katja T1 - Increased record-breaking precipitation events under global warming JF - Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change N2 - In the last decade record-breaking rainfall events have occurred in many places around the world causing severe impacts to human society and the environment including agricultural losses and floodings. There is now medium confidence that human-induced greenhouse gases have contributed to changes in heavy precipitation events at the global scale. Here, we present the first analysis of record-breaking daily rainfall events using observational data. We show that over the last three decades the number of record-breaking events has significantly increased in the global mean. Globally, this increase has led to 12 % more record-breaking rainfall events over 1981-2010 compared to those expected in stationary time series. The number of record-breaking rainfall events peaked in 2010 with an estimated 26 % chance that a new rainfall record is due to long-term climate change. This increase in record-breaking rainfall is explained by a statistical model which accounts for the warming of air and associated increasing water holding capacity only. Our results suggest that whilst the number of rainfall record-breaking events can be related to natural multi-decadal variability over the period from 1901 to 1980, observed record-breaking rainfall events significantly increased afterwards consistent with rising temperatures. Y1 - 2015 U6 - https://doi.org/10.1007/s10584-015-1434-y SN - 0165-0009 SN - 1573-1480 VL - 132 IS - 4 SP - 501 EP - 515 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Lehmann, Jascha A1 - Coumou, Dim A1 - Frieler, Katja T1 - Increased record-breaking precipitation events under global warming (vol 132, pg 501, 2015) T2 - Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change Y1 - 2015 U6 - https://doi.org/10.1007/s10584-015-1466-3 SN - 0165-0009 SN - 1573-1480 VL - 132 IS - 4 SP - 517 EP - 518 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Fromm, T. A1 - Planert, Lars A1 - Jokat, Wilfried A1 - Ryberg, Trond A1 - Behrmann, Jan H. A1 - Weber, Michael H. A1 - Haberland, Christian T1 - South Atlantic opening: A plume-induced breakup? JF - Geology N2 - Upwelling hot mantle plumes are thought to disintegrate continental lithosphere and are considered to be drivers of active continental breakup. The formation of the Walvis Ridge during the opening of the South Atlantic is related to a putative plume-induced breakup. We investigated the crustal structure of the Walvis Ridge (southeast Atlantic Ocean) at its intersection with the continental margin and searched for anomalies related to the possible plume head. The overall structure we identify suggests that no broad plume head existed during opening of the South Atlantic and anomalous mantle melting occurred only locally. We therefore question the importance of a plume head as a driver of continental breakup and further speculate that the hotspot was present before the rifting, leaving a track of kimberlites in the African craton. Y1 - 2015 U6 - https://doi.org/10.1130/G36936.1 SN - 0091-7613 SN - 1943-2682 VL - 43 IS - 10 SP - 931 EP - 934 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Trauth, Martin H. A1 - Bergner, Andreas G. N. A1 - Foerster, Verena A1 - Junginger, Annett A1 - Maslin, Mark A. A1 - Schäbitz, Frank T1 - Episodes of environmental stability versus instability in Late Cenozoic lake records of Eastern Africa JF - Journal of human evolution N2 - Episodes of environmental stability and instability may be equally important for African hominin speciation, dispersal, and cultural innovation. Three examples of a change from stable to unstable environmental conditions are presented on three different time scales: (1) the Mid Holocene (MH) wet dry transition in the Chew Bahir basin (Southern Ethiopian Rift; between 11 ka and 4 ka), (2) the MIS 5-4 transition in the Naivasha basin (Central Kenya Rift; between 160 ka and 50 ka), and (3) the Early Mid Pleistocene Transition (EMPT) in the Olorgesailie basin (Southern Kenya Rift; between 1.25 Ma and 0.4 Ma). A probabilistic age modeling technique is used to determine the timing of these transitions, taking into account possible abrupt changes in the sedimentation rate including episodes of no deposition (hiatuses). Interestingly, the stable-unstable conditions identified in the three records are always associated with an orbitally-induced decrease of insolation: the descending portion of the 800 kyr cycle during the EMPT, declining eccentricity after the 115 ka maximum at the MIS 5-4 transition, and after similar to 10 ka. This observation contributes to an evidence-based discussion of the possible mechanisms causing the switching between environmental stability and instability in Eastern Africa at three different orbital time scales (10,000 to 1,000,000 years) during the Cenozoic. This in turn may lead to great insights into the environmental changes occurring at the same time as hominin speciation, brain expansion, dispersal out of Africa, and cultural innovations and may provide key evidence to build new hypotheses regarding the causes of early human evolution. (C) 2015 Elsevier Ltd. All rights reserved. KW - Paleoclimate KW - East Africa KW - Human evolution KW - Lakes KW - Sediments Y1 - 2015 U6 - https://doi.org/10.1016/j.jhevol.2015.03.011 SN - 0047-2484 VL - 87 SP - 21 EP - 31 PB - Elsevier CY - London ER - TY - JOUR A1 - Heistermann, Maik A1 - Collis, Scott A1 - Dixon, M. J. A1 - Helmus, Jonathan J. A1 - Henja, A. A1 - Michelson, Daniel B. A1 - Pfaff, Thomas T1 - An Open Virtual Machine for Cross-Platform Weather Radar Science JF - Bulletin of the American Meteorological Society N2 - In a recent BAMS article, it is argued that community-based Open Source Software (OSS) could foster scientific progress in weather radar research, and make weather radar software more affordable, flexible, transparent, sustainable, and interoperable.Nevertheless, it can be challenging for potential developers and users to realize these benefits: tools are often cumbersome to install; different operating systems may have particular issues, or may not be supported at all; and many tools have steep learning curves.To overcome some of these barriers, we present an open, community-based virtual machine (VM). This VM can be run on any operating system, and guarantees reproducibility of results across platforms. It contains a suite of independent OSS weather radar tools (BALTRAD, Py-ART, wradlib, RSL, and Radx), and a scientific Python stack. Furthermore, it features a suite of recipes that work out of the box and provide guidance on how to use the different OSS tools alone and together. The code to build the VM from source is hosted on GitHub, which allows the VM to grow with its community.We argue that the VM presents another step toward Open (Weather Radar) Science. It can be used as a quick way to get started, for teaching, or for benchmarking and combining different tools. It can foster the idea of reproducible research in scientific publishing. Being scalable and extendable, it might even allow for real-time data processing.We expect the VM to catalyze progress toward interoperability, and to lower the barrier for new users and developers, thus extending the weather radar community and user base. Y1 - 2015 U6 - https://doi.org/10.1175/BAMS-D-14-00220.1 SN - 0003-0007 SN - 1520-0477 VL - 96 IS - 10 PB - American Meteorological Soc. CY - Boston ER - TY - JOUR A1 - Consorti, Lorenzo A1 - Caus, Esmeralda A1 - Frijia, Gianluca A1 - Yazdi-Moghadam, Mohsen T1 - Praetaberina new genus (type species: Taberina Bingistani Benson, 1948): a stratigraphic marker for the late cenomanian JF - Journal of foraminiferal research N2 - A detailed architectural analysis has been performed on the porcelaneous species Taberina bingistani Henson, 1948 from diverse localities, including its type locality in Iran. Characterized by a subcylindrical to slightly conical shape, with a cribbed apertural face, the Cenomanian Middle-East species bingistani is removed from the American early-Paleogene genus Taberina Keijzer, 1945 (type species: T. cubana) and ascribed to the new genus Praetaberina. In the early stages of growth, the chambers are planispiral-involute, becoming uncoiled in the later stages. The interior of the chambers shows numerous septula and pillars. The septula are radial and distributed in the marginal area of the chamber lumen, while the pillars occupy the central area and are regularly distributed between the intercameral foramina. Pillars are in alignment from one chamber to the next. A new species, from southeast Italy, Praetaberina apula, is also erected. It differs from P. bingistani in its smaller size and significantly reduced structural elements. Both species characterize upper Cenomanian shallow-water deposits. Y1 - 2015 SN - 0096-1191 VL - 45 IS - 4 SP - 378 EP - 389 PB - GeoScienceWorld CY - Cambridge ER - TY - JOUR A1 - Bora, Sanjay Singh A1 - Scherbaum, Frank A1 - Kühn, Nicolas A1 - Stafford, Peter A1 - Edwards, Benjamin T1 - Development of a Response Spectral Ground-Motion Prediction Equation (GMPE) for Seismic-Hazard Analysis from Empirical Fourier Spectral and Duration Models JF - Bulletin of the Seismological Society of America N2 - Empirical ground-motion prediction equations (GMPEs) require adjustment to make them appropriate for site-specific scenarios. However, the process of making such adjustments remains a challenge. This article presents a holistic framework for the development of a response spectral GMPE that is easily adjustable to different seismological conditions and does not suffer from the practical problems associated with adjustments in the response spectral domain. The approach for developing a response spectral GMPE is unique, because it combines the predictions of empirical models for the two model components that characterize the spectral and temporal behavior of the ground motion. Essentially, as described in its initial form by Bora et al. (2014), the approach consists of an empirical model for the Fourier amplitude spectrum (FAS) and a model for the ground-motion duration. These two components are combined within the random vibration theory framework to obtain predictions of response spectral ordinates. In addition, FAS corresponding to individual acceleration records are extrapolated beyond the useable frequencies using the stochastic FAS model, obtained by inversion as described in Edwards and Fah (2013a). To that end, a (oscillator) frequency-dependent duration model, consistent with the empirical FAS model, is also derived. This makes it possible to generate a response spectral model that is easily adjustable to different sets of seismological parameters, such as the stress parameter Delta sigma, quality factor Q, and kappa kappa(0). The dataset used in Bora et al. (2014), a subset of the RESORCE-2012 database, is considered for the present analysis. Based upon the range of the predictor variables in the selected dataset, the present response spectral GMPE should be considered applicable over the magnitude range of 4 <= M-w <= 7.6 at distances <= 200 km. Y1 - 2015 U6 - https://doi.org/10.1785/0120140297 SN - 0037-1106 SN - 1943-3573 VL - 105 IS - 4 SP - 2192 EP - 2218 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Föllmi, Karl B. A1 - Hofmann, Helene A1 - Chiaradia, Massimo A1 - de Kaenel, Eric A1 - Frijia, Gianluca A1 - Parente, Mariano T1 - Miocene phosphate-rich sediments in Salento (southern Italy) JF - Sedimentary geology : international journal of applied and regional sedimentology N2 - The upper Middle to lower Upper Miocene (Serravallian to Tortonian) sedimentary succession in Salento (southern Italy) includes glauconite- and phosphate-rich deposits, which are associated with pelagic micrite. In Baia del Ciolo and Marittima (southern Salento), the succession is composed of shallow-water platform carbonates of Late Oligocene age (Chattian; Porto Badisco Formation), which are overlain by a 20- to 30-cm-thick level of glauconite-rich micrite with abundant reworked particles and fossils of the underlying Porto Badisco Formation. This interval is in turn covered by an up to 15 cm thick phosphatic crust ("Livello ad Aturia"), which itself is overlain either by a hemipelagic chalk-like carbonate of Middle to Late Miocene age ("Pietra Leccese"; Marittima) or directly by a micrite of Late Miocene age (Messinian; Novaglie Formation; Baia del Ciolo), which shallows upwards into a shallow-water platform carbonate. A large hiatus is present in this succession, which likely includes the Lower and lower Middle Miocene. In the region of Lecce, two discrete levels enriched in glauconite and phosphate-each associated with a major discontinuity-occur within the Pietra Leccese. The strontium-isotope ages derived on phosphate nodules and phosphatized and non-phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13.5 and 7.5 Ma, with two clusters at 12 and 10.5 Ma. The glauconite and phosphate-rich sediments resulted from a current-dominated regime, which was characterized by low overall sedimentation rates, erosion and sediment reworking, and authigenesis. This regime was likely related to a generally westward-directed bottom current, which was forced to upwell once it arrived at the western border of the eastern Mediterranean basin. The timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the Mediterranean (Malta, Gozo, southern Sicily, Matese, Latium-Abruzzi platform). The partial diachrony in phosphogenesis may express the effect of lateral switching in and/or focusing of upwelling zones. (C) 2015 Elsevier B.V. All rights reserved. KW - Miocene KW - Salento KW - Italy KW - Phosphogenesis KW - Paleoceanography Y1 - 2015 U6 - https://doi.org/10.1016/j.sedgeo.2015.07.009 SN - 0037-0738 SN - 1879-0968 VL - 327 SP - 55 EP - 71 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wilke, Franziska Daniela Helena A1 - Schmidt, Alexander A1 - Ziemann, Martin Andreas T1 - Subduction, peak and multi-stage exhumation metamorphism: Traces from one coesite-bearing eclogite, Tso Moran, western Himalaya JF - Lithos : an international journal of mineralogy, petrology, and geochemistry N2 - Ultrahigh-pressure (UHP), coesite-bearing edogites in the Himalaya have been documented from the Kaghan Valley in Pakistan and the Tso Morani area in northwest India. These complexes are part of the northern edge of the Indian plate that has been subducted to, and metamorphosed at, mantle depths of more than 100 km before being exhumed. Both UHP complexes are located today directly adjacent to the Indus-Tsangpo suture zone and are not separated by non-metamorphosed sequences of Tethyan sediments from the Asian margin. Herein, we present new data for one fresh coesite-bearing eclogite from the Tso Moran massif. Therein, garnets are zoned reflecting their growth during prograde and peak metamorphism and showing a thin retrograde overgrowth. Inclusions can be directly correlated to the compositional zoning and are seen as either relicts of the protolith mineral paragenesis and as "snap shots" of the mineral paragenesis during subduction and under peak conditions. Rare earth element concentrations (REE) were obtained for garnet, mineral inclusions in garnet and matrix minerals. The REE pattern in garnet reflects a sequential change in matrix minerals and their proportions due to net transfer reactions during subduction and peak metamorphism. Using conventional geothermobarometry, a peak pressure of ca. 44-48 kbar at 560-760 degrees C followed by an S-shaped exhumation curve has been deduced. Gibbs free energy minimization modelling was used to supplement our analytical findings. (C) 2015 Elsevier B.V. All rights reserved. KW - Tso Morari KW - Coesite-bearing eclogite KW - Ultra-high pressure (UHP) KW - Rare earth element (REE) distribution KW - Laser ICP-MS Y1 - 2015 U6 - https://doi.org/10.1016/j.lithos2015.06.007 SN - 0024-4937 SN - 1872-6143 VL - 231 SP - 77 EP - 91 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Aichner, Bernhard A1 - Bussian, Bernd M. A1 - Lehnik-Habrink, Petra A1 - Hein, Sebastian T1 - Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils JF - Environmental pollution N2 - Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to more Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints. (C) 2015 Elsevier Ltd. All rights reserved. KW - Organic pollutants KW - PAHs KW - Soil KW - Emissions KW - Long-range transport KW - Enrichment factor KW - Humic layer KW - Mineral soil KW - O horizon Y1 - 2015 U6 - https://doi.org/10.1016/j.envpol.2015.03.026 SN - 0269-7491 SN - 1873-6424 VL - 203 SP - 31 EP - 39 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Nexer, Maelle A1 - Authemayou, Christine A1 - Schildgen, Taylor F. A1 - Hantoro, Wahyoe S. A1 - Molliex, Stephane A1 - Delcaillau, Bernard A1 - Pedoja, Kevin A1 - Husson, Laurent A1 - Regard, Vincent T1 - Evaluation of morphometric proxies for uplift on sequences of coral reef terraces: A case study from Sumba Island (Indonesia) JF - Geomorphology : an international journal on pure and applied geomorphology N2 - Sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithology make them appropriate to isolate the influence of uplift on drainage morphology. Along the northern coast of Sumba Island, Indonesia, we investigated the correlations between landscape morphology and uplift rates, which range from 0.02 to 0.6 mm.yr(-1). We studied eight morphometric indices at two scales: whole island (similar to 11,000 km(2)) and within sequences of reefal terraces (similar to 3000 km(2)). At the latter scale, we extracted morphometric indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific ranges of uplift rates draining only the reefal terraces. Indices extracted from digital elevation models include residual relief, incision, stream gradient indices (SL and k(sn)), the hypsometric integral, drainage area, mean relief, and the shape factor. We find that SL, the hypsometric integral, mean relief and the shape factor of catchments positively correlate with uplift rates, whereas incision, residual relief, and k(sn) do not. More precisely, we find that only the areas that are uplifting at a rate faster than 03 mm.yr(-1) can yield the extreme values for these indices, implying that these extreme values are indicative of fast uplifting areas. However, the relationship is not bivalent because any uplift rate can be associated with low values of the same indices. For all indices, the transient conditions of the drainage influence the correlation with Pleistocene mean uplift rates, illustrating the necessity to extract morphometric indices with an appropriate choice of catchment scale. This type of analysis helps to identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift, allowing for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates in unstudied coastal zones. (C) 2015 Elsevier B.V. All rights reserved. KW - Drainage morphometry KW - Coral reef terraces KW - Uplift KW - Pleistocene KW - Sumba Island KW - Indonesia Y1 - 2015 U6 - https://doi.org/10.1016/j.geomorph.2015.03.036 SN - 0169-555X SN - 1872-695X VL - 241 SP - 145 EP - 159 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ryberg, Trond A1 - Haberland, Christian A1 - Haberlau, Thomas A1 - Weber, Michael H. A1 - Bauer, Klaus A1 - Behrmann, Jan H. A1 - Jokat, Wilfried T1 - Crustal structure of northwest Namibia: Evidence for plume-rift-continent interaction JF - Geology N2 - The causes for the formation of large igneous provinces and hotspot trails are still a matter of considerable dispute. Seismic tomography and other studies suggest that hot mantle material rising from the core-mantle boundary (CMB) might play a significant role in the formation of such hotspot trails. An important area to verify this concept is the South Atlantic region, with hotspot trails that spatially coincide with one of the largest low-velocity regions at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to form during the separation of the South American and African continents at ca. 130 Ma as a consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to constrain processes of plume-lithosphere interaction and the formation of continental flood basalts (Parana and Etendeka continental flood basalts) and associated intrusive rocks. Our study identified a narrow region (<100 km) of high-seismic-velocity anomalies in the middle and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors connecting the high-velocity body with shallow crustal structures that we speculate to mark potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed massive but localized mafic intrusion into the lower crust results from similar-sized variations in the lithosphere (i.e., lithosphere thickness or preexisting structures). Y1 - 2015 U6 - https://doi.org/10.1130/G36768.1 SN - 0091-7613 SN - 1943-2682 VL - 43 IS - 8 SP - 739 EP - 742 PB - American Institute of Physics CY - Boulder ER - TY - CHAP A1 - Wannek, Dshamilja L. M. A1 - Reimold, Wolf Uwe A1 - Thirlwall, Matthew A1 - Hansen, Bent T. A1 - Schulz, Toni A1 - Hoffmann, Michael A1 - Zaag, Patrice T. A1 - Hauser, Natalia A1 - Siegert, Susann T1 - Are there two types of vredefort granophyre? T2 - Meteoritics & planetary science : journal of the Meteoritical Society Y1 - 2015 SN - 1086-9379 SN - 1945-5100 VL - 50 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Frank, Dorothe A. A1 - Reichstein, Markus A1 - Bahn, Michael A1 - Thonicke, Kirsten A1 - Frank, David A1 - Mahecha, Miguel D. A1 - Smith, Pete A1 - Van der Velde, Marijn A1 - Vicca, Sara A1 - Babst, Flurin A1 - Beer, Christian A1 - Buchmann, Nina A1 - Canadell, Josep G. A1 - Ciais, Philippe A1 - Cramer, Wolfgang A1 - Ibrom, Andreas A1 - Miglietta, Franco A1 - Poulter, Ben A1 - Rammig, Anja A1 - Seneviratne, Sonia I. A1 - Walz, Ariane A1 - Wattenbach, Martin A1 - Zavala, Miguel A. A1 - Zscheischler, Jakob T1 - Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts JF - Global change biology N2 - Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon-climate feedbacks. KW - carbon cycle KW - climate change KW - climate extremes KW - climate variability KW - disturbance KW - terrestrial ecosystems Y1 - 2015 U6 - https://doi.org/10.1111/gcb.12916 SN - 1354-1013 SN - 1365-2486 VL - 21 IS - 8 SP - 2861 EP - 2880 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Lehr, C. A1 - Pöschke, Franziska A1 - Lewandowski, Jörg A1 - Lischeid, Gunnar T1 - A novel method to evaluate the effect of a stream restoration on the spatial pattern of hydraulic connection of stream and groundwater JF - Journal of hydrology N2 - Stream restoration aims at an enhancement of ecological habitats, an increase of water retention within a landscape and sometimes even at an improvement of biogeochemical functions of lotic ecosystems. For the latter, good exchange between groundwater and stream water is often considered to be of major importance. In this study hydraulic connectivity between river and aquifer was investigated for a four years period, covering the restoration of an old oxbow after the second year. The oxbow became reconnected to the stream and the clogging layer in the oxbow was excavated. We expected increasing hydraulic connectivity between oxbow and aquifer after restoration of the stream, and decreasing hydraulic connectivity for the former shortcut due to increased clogging. To test that hypothesis, the spatial and temporal characteristics of the coupled groundwater-stream water system before and after the restoration were analysed by principal component analyses of time series of groundwater heads and stream water levels. The first component depicted between 53% and 70% of the total variance in the dataset for the different years. It captured the propagation of the pressure signal induced by stream water level fluctuations throughout the adjacent aquifer. Thus it could be used as a measure of hydraulic connectivity between stream and aquifer. During the first year, the impact of stream water level fluctuations decreased with distance from the regulated river (shortcut), whereas the hydraulic connection of the oxbow to the adjacent aquifer was very low. After restoration of the stream we observed a slight but not significant increase of hydraulic connectivity in the oxbow in the second year after restoration, but no change for the former shortcut. There is some evidence that the pattern of hydraulic connectivity at the study site is by far more determined by the natural heterogeneity of hydraulic conductivities of the floodplain sediments and the initial construction of the shortcut rather than by the clogging layer in the oxbow. (C) 2015 The Authors. Published by Elsevier B.V. KW - Groundwater-stream water interactions KW - Principal component analysis KW - Signal propagation KW - Hydraulic connectivity KW - Clogging KW - Riparian zone Y1 - 2015 U6 - https://doi.org/10.1016/j.jhydrol.2015.04.075 SN - 0022-1694 SN - 1879-2707 VL - 527 SP - 394 EP - 401 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Karp, Daniel S. A1 - Tallis, Heather A1 - Sachse, Rene A1 - Halpern, Ben A1 - Thonicke, Kirsten A1 - Cramer, Wolfgang A1 - Mooney, Harold A1 - Polasky, Stephen A1 - Tietjen, Britta A1 - Waha, Katharina A1 - Walt, Ariane A1 - Wolny, Stacie T1 - National indicators for observing ecosystem service change JF - Global environmental change : human and policy dimensions N2 - Earth's life-support systems are in rapid decline, yet we have few metrics or indicators with which to track these changes. The world's governments are calling for biodiversity and ecosystem-service monitoring to guide and evaluate international conservation policy as well as to incorporate natural capital into their national accounts. The Group on Earth Observations Biodiversity Observation Network (GEO BON) has been tasked with setting up this monitoring system. Here we explore the immediate feasibility of creating a global ecosystem-service monitoring platform under the GEO BON framework through combining data from national statistics, global vegetation models, and production function models. We found that nine ecosystem services could be annually reported at a national scale in the short term: carbon sequestration, water supply for hydropower, and non-fisheries marine products, crop, livestock, game meat, fisheries, mariculture, and timber production. Reported changes in service delivery over time reflected ecological shocks (e.g., droughts and disease outbreaks), highlighting the immediate utility of this monitoring system. Our work also identified three opportunities for creating a more comprehensive monitoring system. First, investing in input data for ecological process models (e.g., global land-use maps) would allow many more regulating services to be monitored. Currently, only 1 of 9 services that can be reported is a regulating service. Second, household surveys and censuses could help evaluate how nature affects people and provides non-monetary benefits. Finally, to forecast the sustainability of service delivery, research efforts could focus on calculating the total remaining biophysical stocks of provisioning services. Regardless, we demonstrated that a preliminary ecosystem-service monitoring platform is immediately feasible. With sufficient international investment, the platform could evolve further into a much-needed system to track changes in our planet's life-support systems. (C) 2015 Elsevier Ltd. All rights reserved. KW - Ecosystem services KW - GEO BON KW - Global change KW - Monitoring KW - Process models Y1 - 2015 U6 - https://doi.org/10.1016/j.gloenvcha.2015.07.014 SN - 0959-3780 SN - 1872-9495 VL - 35 SP - 12 EP - 21 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Malinowski, Radoslaw A1 - Groom, Geoff A1 - Schwanghart, Wolfgang A1 - Heckrath, Goswin T1 - Detection and Delineation of Localized Flooding from World View-2 Multispectral Data JF - Remote sensing N2 - Remote sensing technology serves as a powerful tool for analyzing geospatial characteristics of flood inundation events at various scales. However, the performance of remote sensing methods depends heavily on the flood characteristics and landscape settings. Difficulties might be encountered in mapping the extent of localized flooding with shallow water on riverine floodplain areas, where patches of herbaceous vegetation are interspersed with open water surfaces. To address the difficulties in mapping inundation on areas with complex water and vegetation compositions, a high spatial resolution dataset has to be used to reduce the problem of mixed pixels. The main objective of our study was to investigate the possibilities of using a single date WorldView-2 image of very high spatial resolution and supporting data to analyze spatial patterns of localized flooding on a riverine floodplain. We used a decision tree algorithm with various combinations of input variables including spectral bands of the WorldView-2 image, selected spectral indices dedicated to mapping water surfaces and vegetation, and topographic data. The overall accuracies of the twelve flood extent maps derived with the decision tree method and performed on both pixels and image objects ranged between 77% and 95%. The highest mapping overall accuracy was achieved with a method that utilized all available input data and the object-based image analysis. Our study demonstrates the possibility of using single date WorldView-2 data for analyzing flooding events at high spatial detail despite the absence of spectral bands from the short-waveform region that are frequently used in water related studies. Our study also highlights the importance of topographic data in inundation analyses. The greatest difficulties were met in mapping water surfaces under dense canopy herbaceous vegetation, due to limited water surface exposure and the dominance of vegetation reflectance. KW - decision tree KW - floodplain KW - inundation KW - localized flooding KW - object-based image analysis KW - wetlands KW - WorldView-2 Y1 - 2015 U6 - https://doi.org/10.3390/rs71114853 SN - 2072-4292 VL - 7 IS - 11 SP - 14853 EP - 14875 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bussian, Bernd M. A1 - Pandelova, Marchela A1 - Lehnik-Habrink, Petra A1 - Aichner, Bernhard A1 - Henkelmann, Bernhard A1 - Schramm, Karl-Werner T1 - Persistent endosulfan sulfate is found with highest abundance among endosulfan I, II, and sulfate in German forest soils JF - Environmental pollution N2 - Endosulfan - an agricultural insecticide and banned by Stockholm Convention - is produced as a 2:1 to 7:3 mixture of isomers endosulfan I (ESI) and endosulfan II (ESII). Endosulfan is transformed under aerobic conditions into endosulfan sulfate (ESS). The study shows for 76 sampling locations in German forests that endosulfan is abundant in all samples with an opposite ratio between the ESI and ESII than the technical product, where the main metabolite ESS is found with even higher abundance. The ratio between ESI/ESII and ESS show clear dependence on the type of stands (coniferous vs. deciduous) and humus type and increases from deciduous via mixed to coniferous forest stands. The study argues for a systematic monitoring of ESI, ESII, and ESS and underlines the need for further research, specifically on the fate of endosulfan including biomagnifications and bioaccumulation in soil. (C) 2015 Elsevier Ltd. All rights reserved. KW - Endosulfan KW - Stockholm-convention KW - Diffuse pollution KW - Soil monitoring KW - Forest soils Y1 - 2015 U6 - https://doi.org/10.1016/j.envpol.2015.08.023 SN - 0269-7491 SN - 1873-6424 VL - 206 SP - 661 EP - 666 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schwab, Valerie F. A1 - Garcin, Yannick A1 - Sachse, Dirk A1 - Todou, Gilbert A1 - Sene, Olivier A1 - Onana, Jean-Michel A1 - Achoundong, Gaston A1 - Gleixner, Gerd T1 - Dinosterol delta D values in stratified tropical lakes (Cameroon) are affected by eutrophication JF - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry N2 - In freshwater settings, dinosterol (4 alpha,23,24-trimethyl-5 alpha-cholest-22E-en-3 beta-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (delta D) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested delta D values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the delta D values of dinosterol correlated with lake water delta D values, confirming a first order influence of source water delta D values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54% compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic-anoxic interface (E-h OAI). The observations suggest that paleohydrologic reconstruction from delta D values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water delta D values, with more positive dinosterol delta values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C-34 botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and beta beta-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with Eh OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol delta D values to evaluate the effect of lake trophic status on sedimentary dinosterol delta D values, as a basis for accurately reconstructing tropical lake water delta D values. (C) 2015 Elsevier Ltd. All rights reserved. KW - Hydrogen KW - Isotope KW - Fractionation KW - Biomarkers KW - Dinosterol KW - Lake KW - Redox potential KW - Paleoenvironmental KW - Proxy Y1 - 2015 U6 - https://doi.org/10.1016/j.orggeochem.2015.08.003 SN - 0146-6380 VL - 88 SP - 35 EP - 49 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zimmermann, Alexander A1 - Uber, Magdalena A1 - Zimmermann, Beate A1 - Levia, Delphis F. T1 - Predictability of stemflow in a species-rich tropical forest JF - Hydrological processes N2 - Numerous studies investigated the influence of abiotic (meteorological conditions) and biotic factors (tree characteristics) on stemflow generation. Although these studies identified the variables that influence stemflow volumes in simply structured forests, the combination of tree characteristics that allows a robust prediction of stemflow volumes in species-rich forests is not well known. Many hydrological applications, however, require at least a rough estimate of stemflow volumes based on the characteristics of a forest stand. The need for robust predictions of stemflow motivated us to investigate the relationships between tree characteristics and stemflow volumes in a species-rich tropical forest located in central Panama. Based on a sampling setup consisting of ten rainfall collectors, 300 throughfall samplers and 60 stemflow collectors and cumulated data comprising 26 rain events, we derive three main findings. Firstly, stemflow represents a minor hydrological component in the studied 1-ha forest patch (1.0% of cumulated rainfall). Secondly, in the studied species-rich forest, single tree characteristics are only weakly related to stemflow volumes. The influence of multiple tree parameters (e.g. crown diameter, presence of large epiphytes and inclination of branches) and the dependencies among these parameters require a multivariate approach to understand the generation of stemflow. Thirdly, predicting stemflow in species-rich forests based on tree parameters is a difficult task. Although our best model can capture the variation in stemflow to some degree, a critical validation reveals that the model cannot provide robust predictions of stemflow. A reanalysis of data from previous studies in species-rich forests corroborates this finding. Based on these results and considering that for most hydrological applications, stemflow is only one parameter among others to estimate, we advocate using the base model, i.e. the mean of the stemflow data, to quantify stemflow volumes for a given study area. Studies in species-rich forests that wish to obtain predictions of stemflow based on tree parameters probably need to conduct a much more extensive sampling than currently implemented by most studies. Copyright (c) 2015 John Wiley & Sons, Ltd. KW - stemflow KW - rainfall partitioning KW - multivariate regression KW - tropical lowland rainforest KW - ecohydrology Y1 - 2015 U6 - https://doi.org/10.1002/hyp.10554 SN - 0885-6087 SN - 1099-1085 VL - 29 IS - 23 SP - 4947 EP - 4956 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Janssen, Annette B. G. A1 - Arhonditsis, George B. A1 - Beusen, Arthur A1 - Bolding, Karsten A1 - Bruce, Louise A1 - Bruggeman, Jorn A1 - Couture, Raoul-Marie A1 - Downing, Andrea S. A1 - Elliott, J. Alex A1 - Frassl, Marieke A. A1 - Gal, Gideon A1 - Gerla, Daan J. A1 - Hipsey, Matthew R. A1 - Hu, Fenjuan A1 - Ives, Stephen C. A1 - Janse, Jan H. A1 - Jeppesen, Erik A1 - Joehnk, Klaus D. A1 - Kneis, David A1 - Kong, Xiangzhen A1 - Kuiper, Jan J. A1 - Lehmann, Moritz K. A1 - Lemmen, Carsten A1 - Oezkundakci, Deniz A1 - Petzoldt, Thomas A1 - Rinke, Karsten A1 - Robson, Barbara J. A1 - Sachse, Rene A1 - Schep, Sebastiaan A. A1 - Schmid, Martin A1 - Scholten, Huub A1 - Teurlincx, Sven A1 - Trolle, Dennis A1 - Troost, Tineke A. A1 - Van Dam, Anne A. A1 - Van Gerven, Luuk P. A. A1 - Weijerman, Mariska A1 - Wells, Scott A. A1 - Mooij, Wolf M. T1 - Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective JF - Aquatic ecology : the international forum covering research in freshwater and marine environments N2 - Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary. KW - Water quality KW - Ecology KW - Geochemistry KW - Hydrology KW - Hydraulics KW - Hydrodynamics KW - Physical environment KW - Socio-economics KW - Model availability KW - Standardization KW - Linking Y1 - 2015 U6 - https://doi.org/10.1007/s10452-015-9544-1 SN - 1386-2588 SN - 1573-5125 VL - 49 IS - 4 SP - 513 EP - 548 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Foerster, Verena A1 - Vogelsang, Ralf A1 - Junginger, Annett A1 - Asrat, Asfawossen A1 - Lamb, Henry F. A1 - Schäbitz, Frank A1 - Trauth, Martin H. T1 - Environmental change and human occupation of southern Ethiopia and northern Kenya during the last 20,000 years JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa. (C) 2015 Elsevier Ltd. All rights reserved. KW - Archeology KW - Paleoclimate KW - African humid period KW - Push factor KW - Adaption KW - Migration KW - Hunter-gatherers KW - Foragers KW - Pastoralism KW - Chew Bahir Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.10.026 SN - 0277-3791 VL - 129 SP - 333 EP - 340 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Musolff, Andreas A1 - Schmidt, Christian A1 - Selle, Benny A1 - Fleckenstein, Jan H. T1 - Catchment controls on solute export JF - Advances in water resources N2 - Dynamics of solute export from catchments can be classified in terms of chemostatic and chemodynamic export regimes by an analysis of concentration-discharge relationships. Previous studies hypothesized that distinct export regimes emerge from the presence of solute mass stores within the catchment and their connectivity to the stream. However, so far a direct link of solute export to identifiable catchment characteristics is missing. Here we investigate long-term time series of stream water quality and quantity of nine neighboring catchments in Central Germany ranging from relatively pristine mountain catchments to agriculturally dominated lowland catchments, spanning large gradients in land use, geology, and climatic conditions. Given the strong collinearity of catchment characteristics we used partial least square regression analysis to quantify the predictive power of these characteristics for median concentrations and the metrics of export regime. We can show that median concentrations and metrics of the export regimes of major ions and nutrients can indeed be inferred from catchment characteristics. Strongest predictors for median concentrations were the share of arable land, discharge per area, runoff coefficient and available water capacity in the root zone of the catchments. The available water capacity in the root zone, the share of arable land being artificially drained and the topographic gradient were found to be the most relevant predictors for the metrics of export regime. These catchment characteristics can represent the size of solute mass store such as the fraction of arable land being a measure for the store of nitrate. On the other hand, catchment characteristics can be a measure for the connectivity of these solute stores to the stream such as the fraction of tile drained land in the catchments. This study demonstrates the potential of data-driven, top down analyses using simple metrics to classify and better understand dominant controls of solute export from catchments. (C) 2015 Elsevier Ltd. All rights reserved. KW - Water quality KW - Catchment KW - Nutrient export KW - Tile drain KW - Export regime KW - Concentration-discharge relationships Y1 - 2015 U6 - https://doi.org/10.1016/j.advwatres.2015.09.026 SN - 0309-1708 SN - 1872-9657 VL - 86 SP - 133 EP - 146 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Goswami, Bedartha A1 - Shekatkar, Snehal M. A1 - Rheinwalt, Aljoscha A1 - Ambika, G. A1 - Kurths, Jürgen T1 - A random interacting network model for complex networks JF - Scientific reports N2 - We propose a RAndom Interacting Network (RAIN) model to study the interactions between a pair of complex networks. The model involves two major steps: (i) the selection of a pair of nodes, one from each network, based on intra-network node-based characteristics, and (ii) the placement of a link between selected nodes based on the similarity of their relative importance in their respective networks. Node selection is based on a selection fitness function and node linkage is based on a linkage probability defined on the linkage scores of nodes. The model allows us to relate within-network characteristics to between-network structure. We apply the model to the interaction between the USA and Schengen airline transportation networks (ATNs). Our results indicate that two mechanisms: degree-based preferential node selection and degree-assortative link placement are necessary to replicate the observed inter-network degree distributions as well as the observed inter-network assortativity. The RAIN model offers the possibility to test multiple hypotheses regarding the mechanisms underlying network interactions. It can also incorporate complex interaction topologies. Furthermore, the framework of the RAIN model is general and can be potentially adapted to various real-world complex systems. Y1 - 2015 U6 - https://doi.org/10.1038/srep18183 SN - 2045-2322 VL - 5 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Wilke, Franziska Daniela Helena A1 - Vieth-Hillebrand, Andrea A1 - Naumann, Rudolf A1 - Erzinger, Jörg A1 - Horsfield, Brian T1 - Induced mobility of inorganic and organic solutes from black shales using water extraction: Implications for shale gas exploitation JF - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry N2 - The study reported here evaluates the degree to which metals, salt anions and organic compounds are released from shales by exposure to water, either in its pure form or mixed with additives commonly employed during shale gas exploitation. The experimental conditions used here were not intended to simulate the exploitation process itself, but nevertheless provided important insights into the effects additives have on solute partition behaviour under oxic to sub-oxic redox conditions. In order to investigate the mobility of major (e.g. Ca, Fe) and trace (e.g. As, Cd, Co, Mo, Pb, U) elements and selected organic compounds, we performed leaching tests with black shale samples from Bornholm, Denmark and Lower Saxony, Germany. Short-term experiments (24 h) were carried out at ambient pressure and temperatures of 100 degrees C using five different lab-made stimulation fluids. Two long-term experiments under elevated pressure and temperature conditions at 100 degrees C/100 bar were performed lasting 6 and 2 months, respectively, using a stimulation fluid containing commercially-available biocide, surfactant, friction reducer and clay stabilizer. Our results show that the amount of dissolved constituents at the end of the experiment is independent of the pH of the stimulation fluid but highly dependent on the composition of the black shale and the buffering capacity of specific components, namely pyrite and carbonates. Shales containing carbonates buffer the solution at pH 7-8. Sulphide minerals (e.g. pyrite) become oxidized and generate sulphuric acid leading to a pH of 2-3. This low pH is responsible for the overall much larger amount of cations dissolved from shales containing pyrite but little to no carbonate. The amount of elements released into the fluid is also dependent on the residence time, since as much as half of the measured 23 elements show highest concentrations within four days. Afterwards, the concentration of most of the elemental species decreased pointing to secondary precipitations. Generally, in our experiments less than 15% of each analysed element contained in the black shale was mobilised into the fluid. (C) 2015 Elsevier Ltd. All rights reserved. KW - Unconventional gas KW - Black shales KW - Stimulation fluids KW - Element mobility KW - Batch experiments Y1 - 2015 U6 - https://doi.org/10.1016/j.apgeochem.2015.07.008 SN - 0883-2927 VL - 63 SP - 158 EP - 168 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Rohrmann, Alexander A1 - Heermance, Richard A1 - Kapp, Paul A1 - Cai, Fulong T1 - Wind as the primary driver of erosion in the Qaidam Basin, China (vol 374, pg 1, 2013) T2 - Earth & planetary science letters Y1 - 2015 U6 - https://doi.org/10.1016/j.epsl.2015.10.011 SN - 0012-821X SN - 1385-013X VL - 432 SP - 501 EP - 501 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Cesare, Bernardo A1 - Acosta-Vigil, Antonio A1 - Bartoli, Omar A1 - Ferrero, Silvio T1 - What can we learn from melt inclusions in migmatites and granulites? JF - Lithos : an international journal of mineralogy, petrology, and geochemistry N2 - With less than two decades of activity, research on melt inclusions (MI) in crystals from rocks that have undergone crustal anatexis - migmatites and granulites - is a recent addition to crustal petrology and geochemistry. Studies on this subject started with glassy inclusions in anatectic crustal enclaves in lavas, and then progressed to regionally metamorphosed and partially melted crustal rocks, where melt inclusions are normally crystallized into a cryptocrystalline aggregate (nanogranitoid). Since the first paper on melt inclusions in the granulites of the Kerala Khondalite Belt in 2009, reported and studied occurrences are already a few tens. Melt inclusions in migmatites and granulites show many analogies with their more common and long studied counterparts in igneous rocks, but also display very important differences and peculiarities, which are the subject of this review. Microstructurally, melt inclusions in anatectic rocks are small, commonly 10 mu m in diameter, and their main mineral host is peritectic garnet, although several other hosts have been observed. Inclusion contents vary from glass in enclaves that were cooled very rapidly from supersolidus temperatures, to completely crystallized material in slowly cooled regional migmatites. The chemical composition of the inclusions can be analyzed combining several techniques (SEM, EMP, NanoSIMS, LA-ICP-MS), but in the case of crystallized inclusions the experimental remelting under confining pressure in a piston cylinder is a prerequisite. The melt is generally granitic and peraluminous, although granodioritic to trondhjemitic compositions have also been found. Being mostly primary in origin, inclusions attest for the growth of their peritectic host in the presence of melt. As a consequence, the inclusions have the unique ability of preserving information on the composition of primary anatectic crustal melts, before they undergo any of the common following changes in their way to produce crustal magmas. For these peculiar features, melt inclusions in migmatites and granulites, largely overlooked so far, have the potential to become a fundamental tool for the study of crustal melting, crustal differentiation, and even the generation of the continental crust. (C) 2015 The Authors. Published by Elsevier B.V. KW - Melt inclusions KW - Migmatites KW - Granulites KW - Granites KW - Crustal melting KW - Nanogranitoids Y1 - 2015 U6 - https://doi.org/10.1016/j.lithos.2015.09.028 SN - 0024-4937 SN - 1872-6143 VL - 239 SP - 186 EP - 216 PB - Elsevier CY - Amsterdam ER -