@article{LueckRuehlmannKirchmann2011, author = {L{\"u}ck, Erika and R{\"u}hlmann, J{\"o}rg and Kirchmann, Holger}, title = {Properties of soils from the Swedish long-term fertility experiments VI. Mapping soil electrical conductivity with different geophysical methods}, series = {Acta agriculturae Scandinavica : Section B, Soil and plant science}, volume = {61}, journal = {Acta agriculturae Scandinavica : Section B, Soil and plant science}, number = {5}, publisher = {Taylor \& Francis Group}, address = {Oslo}, issn = {0906-4710}, doi = {10.1080/09064710.2010.502124}, pages = {438 -- 447}, year = {2011}, abstract = {Swedish long-term soil fertility experiments were used to investigate the effect of texture and fertilization regime on soil electrical conductivity. In one geophysical approach, fields were mapped to characterize the horizontal variability in apparent electrical conductivity down to 1.5 m soil depth using an electromagnetic induction meter (EM38 device). The data obtained were geo-referenced by dGPS. The other approach consisted of measuring the vertical variability in electrical conductivity along transects using a multi-electrode apparatus for electrical resistivity tomography (GeoTom RES/IP device) down to 2 m depth. Geophysical field work was complemented by soil analyses. The results showed that despite 40 years of different fertilization regimes, treatments had no significant effects on the apparent electrical conductivity. Instead, the comparison of sites revealed high and low conductivity soils, with gradual differences explained by soil texture. A significant, linear relationship found between apparent electrical conductivity and soil clay content explained 80\% of the variability measured. In terms of soil depth, both low and high electrical conductivity values were measured. Abrupt changes in electrical conductivity within a field revealed the presence of 'deviating areas'. Higher values corresponded well with layers with a high clay content, while local inclusions of coarse-textured materials caused a high variability in conductivity in some fields. The geophysical methods tested provided useful information on the variability in soil texture at the experimental sites. The use of spatial EC variability as a co-variable in statistical analysis could be a complementary tool in the evaluation of experimental results.}, language = {en} } @article{KonradSchmolkeO'BrienZack2011, author = {Konrad-Schmolke, Matthias and O'Brien, Patrick J. and Zack, Thomas}, title = {Fluid Migration above a Subducted Slab-Constraints on Amount, Pathways and Major Element Mobility from Partially Overprinted Eclogite-facies Rocks (Sesia Zone, Western Alps)}, series = {Journal of petrology}, volume = {52}, journal = {Journal of petrology}, number = {3}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0022-3530}, doi = {10.1093/petrology/egq087}, pages = {457 -- 486}, year = {2011}, abstract = {The Western Alpine Sesia-Lanzo Zone (SLZ) is a sliver of eclogite-facies continental crust exhumed from mantle depths in the hanging wall of a subducted oceanic slab. Eclogite-facies felsic and basic rocks sampled across the internal SLZ show different degrees of retrograde metamorphic overprint associated with fluid influx. The weakly deformed samples preserve relict eclogite-facies mineral assemblages that show partial fluid-induced compositional re-equilibration along grain boundaries, brittle fractures and other fluid pathways. Multiple fluid influx stages are indicated by replacement of primary omphacite by phengite, albitic plagioclase and epidote as well as partial re-equilibration and/or overgrowths in phengite and sodic amphibole, producing characteristic step-like compositional zoning patterns. The observed textures, together with the map-scale distribution of the samples, suggest open-system, pervasive and reactive fluid flux across large rock volumes above the subducted slab. Thermodynamic modelling indicates a minimum amount of fluid of 0 center dot 1-0 center dot 5 wt \% interacting with the wall-rocks. Phase relations and reaction textures indicate mobility of K, Ca, Fe and Mg, whereas Al is relatively immobile in these medium-temperature-high-pressure fluids. Furthermore, the thermodynamic models show that recycling of previously fractionated material, such as in the cores of garnet porphyroblasts, largely controls the compositional re-equilibration of the exhumed rock body.}, language = {en} } @article{KonradSchmolkeZackO'Brienetal.2011, author = {Konrad-Schmolke, Matthias and Zack, Thomas and O'Brien, Patrick J. and Barth, Matthias}, title = {Fluid migration above a subducted slab - Thermodynamic and trace element modelling of fluid-rock interaction in partially overprinted eclogite-facies rocks (Sesia Zone, Western Alps)}, series = {Earth \& planetary science letters}, volume = {311}, journal = {Earth \& planetary science letters}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.09.025}, pages = {287 -- 298}, year = {2011}, abstract = {The amount and composition of subduction zone fluids and the effect of fluid-rock interaction at a slab-mantle interface have been constrained by thermodynamic and trace element modelling of partially overprinted blueschist-facies rocks from the Sesia Zone (Western Alps). Deformation-induced differences in fluid flux led to a partial preservation of pristine mineral cores in weakly deformed samples that were used to quantify Li, B, Stand Pb distribution during mineral growth, -breakdown and modification induced by fluid-rock interaction. Our results show that Li and 13 budgets are fluid-controlled, thus acting as tracers for fluid-rock interaction processes, whereas Stand Pb budgets are mainly controlled by the fluid-induced formation of epidote. Our calculations show that fluid-rock interaction caused significant Li and B depletion in the affected rocks due to leaching effects, which in turn can lead to a drastic enrichment of these elements in the percolating fluid. Depending on available fluid-mineral trace element distribution coefficients modelled fluid rock ratios were up to 0.06 in weakly deformed samples and at least 0.5 to 4 in shear zone mylonites. These amounts lead to time integrated fluid fluxes of up to 1.4-10(2) m(3) m(-2) in the weakly deformed rocks and 1-8-10(3) m(3) m(-2) in the mylonites. Combined thermodynamic and trace element models can be used to quantify metamorphic fluid fluxes and the associated element transfer in complex, reacting rock systems and help to better understand commonly observed fluid-induced trace element trends in rocks and minerals from different geodynamic environments.}, language = {en} } @article{SchmidtMezgerO'Brien2011, author = {Schmidt, Alexander and Mezger, Klaus and O'Brien, Patrick J.}, title = {The time of eclogite formation in the ultrahigh pressure rocks of the Sulu terrane Constraints from Lu-Hf garnet geochronology}, series = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, volume = {125}, journal = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0024-4937}, doi = {10.1016/j.lithos.2011.04.004}, pages = {743 -- 756}, year = {2011}, abstract = {Eclogites from the main borehole of the Chinese Continental Scientific Drilling project yield highly precise Lu-Hf garnet-clinopyroxene ages of 216.9 +/- 1.2 Ma (four samples) and 220.5 +/- 2.7 Ma (one sample). The spatial distribution of the rare earth elements in garnet is consistent with the preservation of primary growth zoning, unmodified by diffusion, which supports the interpretation that the Lu-Hf ages date the time of formation of garnet, the major rock forming mineral in the eclogites. The preservation of primary REE-zoning, despite peak metamorphic temperatures around 800-850 degrees C. indicates that the Lu-Hf chronometer is perfectly suitable to date garnet-forming reactions in high grade rocks. The range of Lu-Hf ages for eclogites in the Dabie-Sulu UHP terrane point to episodic rather than continuous growth of garnets and thus punctuated metamorphism during the collision of the North China Block and the Yangtze Block. The U-Pb ages and Hf-isotope systematics of zircon grains from one eclogite sample imply a protracted geologic history of the eclogite precursors that started around 2 Ga and culminated in the UHP metamorphism around 220 Ma.}, language = {en} } @article{KotkovaO'BrienZiemann2011, author = {Kotkova, Jana and O'Brien, Patrick J. and Ziemann, Martin Andreas}, title = {Diamond and coesite discovered in Saxony-type granulite solution to the Variscan garnet peridotite enigma}, series = {Geology}, volume = {39}, journal = {Geology}, number = {7}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G31971.1}, pages = {667 -- 670}, year = {2011}, abstract = {The pressures required for diamond and coesite formation far exceed conditions reached by even the deepest present-day orogenic crustal roots. Therefore the occurrence of metamorphosed continental crust containing these minerals requires processes other than crustal thickening to have operated in the past. Here we report the first in situ finding of diamond and coesite, characterized by micro-Raman spectroscopy, in high-pressure granulites otherwise indistinguishable from granulites found associated with garnet peridotite throughout the European Variscides. Our discovery confirms the provenance of Europe's first reliable diamond, the "Bohemian diamond," found in A.D. 1870, and also represents the first robust evidence for ultrahigh-pressure conditions in a major Variscan crustal rock type. A process of deep continental subduction is required to explain the metamorphic pressures and the granulite-garnet peridotite association, and thus tectonometamorphic models for these rocks involving a deep orogenic crustal root need to be significantly modified.}, language = {en} } @phdthesis{Grochowska2011, author = {Grochowska, Marta}, title = {{\"O}konomische, soziale und r{\"a}umliche Folgen der saisonalen Arbeitsmigration im Herkunftsgebiet : am Beispiel der Region Konin (Polen)}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-137-0}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-49649}, school = {Universit{\"a}t Potsdam}, pages = {390}, year = {2011}, abstract = {Die vorliegende Arbeit basiert auf Forschungen in den Jahren 2007-2009. Sie betrachtet die saisonale Arbeitsmigration aus der polnischen Region Konin, wo die Arbeitsmigration aus {\"o}konomischen Gr{\"u}nden, wie auch in {\"a}hnlich strukturierten Gebieten Polens, eine lange Tradition hat, die bis ins 19. Jahrhundert zur{\"u}ckgeht. Sie wird die saisonale Migration ins Ausland mit den {\"o}konomischen, sozialen und r{\"a}umlichen Auswirkungen aus der Perspektive des Einzelnen und seiner unmittelbaren Umgebung, aber auch der Gesellschaft und Herkunftsgebiet der Migranten betrachtet.}, language = {de} } @phdthesis{Wulf2011, author = {Wulf, Hendrik}, title = {Seasonal precipitation, river discharge, and sediment flux in the western Himalaya}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57905}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Rainfall, snow-, and glacial melt throughout the Himalaya control river discharge, which is vital for maintaining agriculture, drinking water and hydropower generation. However, the spatiotemporal contribution of these discharge components to Himalayan rivers is not well understood, mainly because of the scarcity of ground-based observations. Consequently, there is also little known about the triggers and sources of peak sediment flux events, which account for extensive hydropower reservoir filling and turbine abrasion. We therefore lack basic information on the distribution of water resources and controls of erosion processes. In this thesis, I employ various methods to assess and quantify general characteristics of and links between precipitation, river discharge, and sediment flux in the Sutlej Valley. First, I analyze daily precipitation data (1998-2007) from 80 weather stations in the western Himalaya, to decipher the distribution of rain- and snowfall. Rainfall magnitude frequency analyses indicate that 40\% of the summer rainfall budget is attributed to monsoonal rainstorms, which show higher variability in the orogenic interior than in frontal regions. Combined analysis of rainstorms and sediment flux data of a major Sutlej River tributary indicate that monsoonal rainfall has a first order control on erosion processes in the orogenic interior, despite the dominance of snowfall in this region. Second, I examine the contribution of rainfall, snow and glacial melt to river discharge in the Sutlej Valley (s55,000 km2), based on a distributed hydrological model, which covers the period 2000-2008. To achieve high spatial and daily resolution despite limited ground-based observations the hydrological model is forced by daily remote sensing data, which I adjusted and calibrated with ground station data. The calibration shows that the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product systematically overestimates rainfall in semi-arid and arid regions, increasing with aridity. The model results indicate that snowmelt-derived discharge (74\%) is most important during the pre-monsoon season (April to June) whereas rainfall (56\%) and glacial melt (17\%) dominate the monsoon season (July-September). Therefore, climate change most likely causes a reduction in river discharge during the pre-monsoon season, which especially affects the orogenic interior. Third, I investigate the controls on suspended sediment flux in different parts of the Sutlej catchments, based on daily gauging data from the past decade. In conjunction with meteorological data, earthquake records, and rock strength measurements I find that rainstorms are the most frequent trigger of high-discharge events with peaks in suspended sediment concentrations (SSC) that account for the bulk of the suspended sediment flux. The suspended sediment flux increases downstream, mainly due to increases in runoff. Pronounced erosion along the Himalayan Front occurs throughout the monsoon season, whereas efficient erosion of the orogenic interior is confined to single extreme events. The results of this thesis highlight the importance of snow and glacially derived melt waters in the western Himalaya, where extensive regions receive only limited amounts of monsoonal rainfall. These regions are therefore particularly susceptible to global warming with major implications on the hydrological cycle. However, the sediment discharge data show that infrequent monsoonal rainstorms that pass the orographic barrier of the Higher Himalaya are still the primary trigger of the highest-impact erosion events, despite being subordinate to snow and glacially-derived discharge. These findings may help to predict peak sediment flux events and could underpin the strategic development of preventative measures for hydropower infrastructures.}, language = {en} } @phdthesis{Wichura2011, author = {Wichura, Henry}, title = {Topographic evolution of the East African Plateau : a combined study on lava-flow modeling and paleo-topography}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52363}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The East African Plateau provides a spectacular example of geodynamic plateau uplift, active continental rifting, and associated climatic forcing. It is an integral part of the East African Rift System and has an average elevation of approximately 1,000 m. Its location coincides with a negative Bouguer gravity anomaly with a semi-circular shape, closely related to a mantle plume, which influences the Cenozoic crustal development since its impingement in Eocene-Oligocene time. The uplift of the East African Plateau, preceding volcanism, and rifting formed an important orographic barrier and tectonically controlled environment, which is profoundly influenced by climate driven processes. Its location within the equatorial realm supports recently proposed hypotheses, that topographic changes in this region must be considered as the dominant forcing factor influencing atmospheric circulation patterns and rainfall distribution. The uplift of this region has therefore often been associated with fundamental climatic and environmental changes in East Africa and adjacent regions. While the far-reaching influence of the plateau uplift is widely accepted, the timing and the magnitude of the uplift are ambiguous and are still subject to ongoing discussion. This dilemma stems from the lack of datable, geomorphically meaningful reference horizons that could record surface uplift. In order to quantify the amount of plateau uplift and to find evidence for the existence of significant relief along the East African Plateau prior to rifting, I analyzed and modeled one of the longest terrestrial lava flows; the 300-km-long Yatta phonolite flow in Kenya. This lava flow is 13.5 Ma old and originated in the region that now corresponds to the eastern rift shoulders. The phonolitic flow utilized an old riverbed that once drained the eastern flank of the plateau. Due to differential erosion this lava flow now forms a positive relief above the parallel-flowing Athi River, which is mimicking the course of the paleo-river. My approach is a lava-flow modeling, based on an improved composition and temperature dependent method to parameterize the flow of an arbitrary lava in a rectangular-shaped channel. The essential growth pattern is described by a one-dimensional model, in which Newtonian rheological flow advance is governed by the development of viscosity and/or velocity in the internal parts of the lava-flow front. Comparing assessments of different magma compositions reveal that length-dominated, channelized lava flows are characterized by high effusion rates, rapid emplacement under approximately isothermal conditions, and laminar flow. By integrating the Yatta lava flow dimensions and the covered paleo-topography (slope angle) into the model, I was able to determine the pre-rift topography of the East African Plateau. The modeling results yield a pre-rift slope of at least 0.2°, suggesting that the lava flow must have originated at a minimum elevation of 1,400 m. Hence, high topography in the region of the present-day Kenya Rift must have existed by at least 13.5 Ma. This inferred mid-Miocene uplift coincides with the two-step expansion of grasslands, as well as important radiation and speciation events in tropical Africa. Accordingly, the combination of my results regarding the Yatta lava flow emplacement history, its location, and its morphologic character, validates it as a suitable "paleo-tiltmeter" and has thus to be considered as an important topographic and volcanic feature for the topographic evolution in East Africa.}, language = {en} } @phdthesis{Polanski2011, author = {Polanski, Stefan}, title = {Simulation der indischen Monsunzirkulation mit dem Regionalen Klimamodell HIRHAM}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52508}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {In dieser Arbeit wird das regionale Klimamodell HIRHAM mit einer horizontalen Aufl{\"o}sung von 50 km und 19 vertikalen Schichten erstmals auf den asiatischen Kontinent angewendet, um die indische Monsunzirkulation unter rezenten und pal{\"a}oklimatischen Bedingungen zu simulieren. Das Integrationsgebiet des Modells erstreckt sich von etwa 0ºN - 50ºN und 42ºE - 110ºE und bedeckt dabei sowohl die hohe Topographie des Himalajas und Tibet Plateaus als auch den n{\"o}rdlichen Indischen Ozean. Das Ziel besteht in der Beschreibung der regionalen Kopplung zwischen der Monsunzirkulation und den orographischen sowie diabatischen Antriebsmechanismen. Eine 44-j{\"a}hrige Modellsimulation von 1958-2001, die am seitlichen und unteren Rand von ECMWF Reanalysen (ERA40) angetrieben wird, bildet die Grundlage f{\"u}r die Validierung der Modellergebnisse mit Beobachtungen auf der Basis von Stations- und Gitterdatens{\"a}tzen. Der Fokus liegt dabei auf der atmosph{\"a}rischen Zirkulation, der Temperatur und dem Niederschlag im Sommer- und Wintermonsun, wobei die Qualit{\"a}t des Modells sowohl in Bezug zur langfristigen und dekadischen Klimatologie als auch zur interannuellen Variabilit{\"a}t evaluiert wird. Im Zusammenhang mit einer realistischen Reproduktion der Modelltopographie kann f{\"u}r die Muster der Zirkulation und Temperatur eine gute {\"U}bereinstimmung zwischen Modell und Daten nachgewiesen werden. Der simulierte Niederschlag zeigt eine bessere {\"U}bereinstimmung mit einem hoch aufgel{\"o}sten Gitterdatensatz {\"u}ber der Landoberfl{\"a}che Zentralindiens und in den Hochgebirgsregionen, der den Vorteil des Regionalmodells gegen{\"u}ber der antreibenden Reanalyse hervorhebt. In verschiedenen Fall- und Sensitivit{\"a}tsstudien werden die wesentlichen Antriebsfaktoren des indischen Monsuns (Meeresoberfl{\"a}chentemperaturen, St{\"a}rke des winterlichen Sibirischen Hochs und Anomalien der Bodenfeuchte) untersucht. Die Ergebnisse machen deutlich, dass die Simulation dieser Mechanismen auch mit einem Regionalmodell sehr schwierig ist, da die Komplexit{\"a}t des Monsunsystems hochgradig nichtlinear ist und die vor allem subgridskalig wirkenden Prozesse im Modell noch nicht ausreichend parametrisiert und verstanden sind. Ein pal{\"a}oklimatisches Experiment f{\"u}r eine 44-j{\"a}hrige Zeitscheibe im mittleren Holoz{\"a}n (etwa 6000 Jahre vor heute), die am Rand von einer globalen ECHAM5 Simulation angetrieben wird, zeigt markante Ver{\"a}nderungen in der Intensit{\"a}t des Monsuns durch die unterschiedliche solare Einstrahlung, die wiederum Einfl{\"u}sse auf die SST, die Zirkulation und damit auf die Niederschlagsmuster hat.}, language = {de} } @article{PilzParolaiStupazzinietal.2011, author = {Pilz, Marco and Parolai, Stefano and Stupazzini, Marco and Paolucci, Roberto and Zschau, Jochen}, title = {Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code}, series = {Geophysical journal international}, volume = {187}, journal = {Geophysical journal international}, number = {2}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2011.05183.x}, pages = {929 -- 945}, year = {2011}, abstract = {Simulations of strong ground motion within the Santiago de Chile Metropolitan area were carried out by means of 3-D deterministic wave propagation tool based on the spectral element method. The simulated events take into account the pronounced interface between the low-velocity sedimentary basin and the bedrock as well as topography of the area. To verify our model we simulated a regional earthquake recorded by a dense network installed in the city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical M(w) = 6.0 event occurring along the active San Ramon Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed shaking pattern.}, language = {en} } @article{PilzParolaiPicozzietal.2011, author = {Pilz, Marco and Parolai, Stefano and Picozzi, Matteo and Zschau, Jochen}, title = {Evaluation of proxies for seismic site conditions in large urban areas the example of Santiago de Chile}, series = {Physics and chemistry of the earth}, volume = {36}, journal = {Physics and chemistry of the earth}, number = {16}, publisher = {Elsevier}, address = {Oxford}, issn = {1474-7065}, doi = {10.1016/j.pce.2011.01.007}, pages = {1259 -- 1266}, year = {2011}, abstract = {Characterizing the local site response in large cities is an important step towards seismic hazard assessment. To this regard, single station seismic noise measurements were carried out at 146 sites in the northern part of Santiago de Chile. This extensive survey allowed the fundamental resonance frequency of the sedimentary cover, derived from horizontal-to-vertical (H/V) spectral ratios, to be mapped. By inverting the spectral ratios under the constraint of the thickness of the sedimentary cover, known from previous gravimetric measurements, local S-wave velocity profiles have been retrieved. After interpolation between the individual profiles, the resulting high resolution 3D S-wave velocity model allows the entire area, as well as deeper parts of the basin, to be represented in great detail. Since one lithology shows a great scatter in the velocity values only a very general correlation between S-wave velocity in the uppermost 30 m (v(s)(30)) and local geology is found. Local S-wave velocity profiles can serve as a key factor in seismic hazard assessment, since they allow an estimate of the amplification potential of the sedimentary cover. Mapping the intensity distribution of the 27 February 2010 Maule, Chile, event (Mw = 8.8) the results indicate that local amplification of the ground motion might partially explain the damage distribution and encourage the use of the low cost seismic noise techniques for the study of seismic site effects.}, language = {en} } @phdthesis{Hainzl2011, author = {Hainzl, Sebastian}, title = {Earthquake triggering and interaction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-50095}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Earthquake faults interact with each other in many different ways and hence earthquakes cannot be treated as individual independent events. Although earthquake interactions generally lead to a complex evolution of the crustal stress field, it does not necessarily mean that the earthquake occurrence becomes random and completely unpredictable. In particular, the interplay between earthquakes can rather explain the occurrence of pronounced characteristics such as periods of accelerated and depressed seismicity (seismic quiescence) as well as spatiotemporal earthquake clustering (swarms and aftershock sequences). Ignoring the time-dependence of the process by looking at time-averaged values - as largely done in standard procedures of seismic hazard assessment - can thus lead to erroneous estimations not only of the activity level of future earthquakes but also of their spatial distribution. Therefore, it exists an urgent need for applicable time-dependent models. In my work, I aimed at better understanding and characterization of the earthquake interactions in order to improve seismic hazard estimations. For this purpose, I studied seismicity patterns on spatial scales ranging from hydraulic fracture experiments (meter to kilometer) to fault system size (hundreds of kilometers), while the temporal scale of interest varied from the immediate aftershock activity (minutes to months) to seismic cycles (tens to thousands of years). My studies revealed a number of new characteristics of fluid-induced and stress-triggered earthquake clustering as well as precursory phenomena in earthquake cycles. Data analysis of earthquake and deformation data were accompanied by statistical and physics-based model simulations which allow a better understanding of the role of structural heterogeneities, stress changes, afterslip and fluid flow. Finally, new strategies and methods have been developed and tested which help to improve seismic hazard estimations by taking the time-dependence of the earthquake process appropriately into account.}, language = {en} } @phdthesis{Graeff2011, author = {Gr{\"a}ff, Thomas}, title = {Soil moisture dynamics and soil moisture controlled runoff processes at different spatial scales : from observation to modelling}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-54470}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Soil moisture is a key state variable that controls runoff formation, infiltration and partitioning of radiation into latent and sensible heat. However, the experimental characterisation of near surface soil moisture patterns and their controls on runoff formation remains a challenge. This subject was one aspect of the BMBF-funded OPAQUE project (operational discharge and flooding predictions in head catchments). As part of that project the focus of this dissertation is on: (1) testing the methodology and feasibility of the Spatial TDR technology in producing soil moisture profiles along TDR probes, including an inversion technique of the recorded signal in heterogeneous field soils, (2) the analysis of spatial variability and temporal dynamics of soil moisture at the field scale including field experiments and hydrological modelling, (3) the application of models of different complexity for understanding soil moisture dynamics and its importance for runoff generation as well as for improving the prediction of runoff volumes. To fulfil objective 1, several laboratory experiments were conducted to understand the influence of probe rod geometry and heterogeneities in the sampling volume under different wetness conditions. This includes a detailed analysis on how these error sources affect retrieval of soil moisture profiles in soils. Concerning objective 2 a sampling strategy of two TDR clusters installed in the head water of the Wilde Weißeritz catchment (Eastern Ore Mountains, Germany) was used to investigate how well "the catchment state" can be characterised by means of distributed soil moisture data observed at the field scale. A grassland site and a forested site both located on gentle slopes were instrumented with two Spatial TDR clusters that consist of up to 39 TDR probes. Process understanding was gained by modelling the interaction of evapotranspiration and soil moisture with the hydrological process model CATFLOW. A field scale irrigation experiment was carried out to investigate near subsurface processes at the hillslope scale. The interactions of soil moisture and runoff formation were analysed using discharge data from three nested catchments: the Becherbach with a size of 2 km², the Rehefeld catchment (17 km²) and the superordinate Ammelsdorf catchment (49 km²). Statistical analyses including observations of pre-event runoff, soil moisture and different rainfall characteristics were employed to predict stream flow volume. On the different scales a strong correlation between the average soil moisture and the runoff coefficients of rainfall-runoff events could be found, which almost explains equivalent variability as the pre-event runoff. Furthermore, there was a strong correlation between surface soil moisture and subsurface wetness with a hysteretic behaviour between runoff soil moisture. To fulfil objective 3 these findings were used in a generalised linear model (GLM) analysis which combines state variables describing the catchments antecedent wetness and variables describing the meteorological forcing in order to predict event runoff coefficients. GLM results were compared to simulations with the catchment model WaSiM ETH. Hereby were the model results of the GLMs always better than the simulations with WaSiM ETH. The GLM analysis indicated that the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore soil moisture controls on runoff generation and can be an important link between the scales. Long term monitoring of such sites could yield valuable information for flood warning and forecasting by identifying critical soil moisture conditions for the former and providing a better representation of the initial moisture conditions for the latter.}, language = {en} } @article{Lederer2011, author = {Lederer, Markus}, title = {From CDM to REDD+ - what do we know for setting up effective and legitimate carbon governance?}, series = {Ecological economics}, volume = {70}, journal = {Ecological economics}, number = {11}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0921-8009}, doi = {10.1016/j.ecolecon.2011.02.003}, pages = {1900 -- 1907}, year = {2011}, abstract = {This article compares two carbon governance instruments - the Clean Development Mechanism (CDM) and Reducing Emissions from Deforestation and Degradation (REDD+) - to assess lessons from the former for the latter regarding effectiveness and legitimacy of such instruments. The article argues that the CDM has a relatively high degree of output-oriented legitimacy resulting in effectiveness and some input-oriented legitimacy, with few discernible tradeoffs between them. In contrasting this to REDD+, the hypotheses are advanced that (i) output-oriented legitimacy/effectiveness can again be achieved but that (ii) a higher degree of input-oriented legitimacy is necessary for REDD+ and thus also a certain trade-off between the two forms of legitimacy can be expected. This is shown through comparing the technologies and methodologies, economic rationales, political support, regulatory structures, and environmental impacts of both instruments.}, language = {en} } @article{ShebalinNarteauHolschneideretal.2011, author = {Shebalin, Peter and Narteau, Clement and Holschneider, Matthias and Schorlemmer, Danijel}, title = {Short-Term earthquake forecasting using early aftershock statistics}, series = {Bulletin of the Seismological Society of America}, volume = {101}, journal = {Bulletin of the Seismological Society of America}, number = {1}, publisher = {Seismological Society of America}, address = {El Cerrito}, issn = {0037-1106}, doi = {10.1785/0120100119}, pages = {297 -- 312}, year = {2011}, abstract = {We present an alarm-based earthquake forecast model that uses the early aftershock statistics (EAST). This model is based on the hypothesis that the time delay before the onset of the power-law aftershock decay rate decreases as the level of stress and the seismogenic potential increase. Here, we estimate this time delay from < t(g)>, the time constant of the Omori-Utsu law. To isolate space-time regions with a relative high level of stress, the single local variable of our forecast model is the E-a value, the ratio between the long-term and short-term estimations of < t(g)>. When and where the E-a value exceeds a given threshold (i.e., the c value is abnormally small), an alarm is issued, and an earthquake is expected to occur during the next time step. Retrospective tests show that the EAST model has better predictive power than a stationary reference model based on smoothed extrapolation of past seismicity. The official prospective test for California started on 1 July 2009 in the testing center of the Collaboratory for the Study of Earthquake Predictability (CSEP). During the first nine months, 44 M >= 4 earthquakes occurred in the testing area. For this time period, the EAST model has better predictive power than the reference model at a 1\% level of significance. Because the EAST model has also a better predictive power than several time-varying clustering models tested in CSEP at a 1\% level of significance, we suggest that our successful prospective results are not due only to the space-time clustering of aftershocks.}, language = {en} } @phdthesis{Ulrich2011, author = {Ulrich, Mathias}, title = {Permafrost landform studies on Earth : Implications for periglacial landscape evolution and habitability on Mars}, address = {Potsdam}, pages = {VIII, 160 S.}, year = {2011}, language = {en} } @phdthesis{Fernandoy2011, author = {Fernandoy, Francisco}, title = {Recent climate variability at the Antartica Peninsula and coastal Dronning Maud Land, based on stable water isotope data}, address = {Potsdam}, pages = {113 S.}, year = {2011}, language = {en} } @phdthesis{Fader2011, author = {Fader, Marianela}, title = {Flows of virtual land and water throught global trade of agricultural products}, address = {Potsdam}, pages = {117 S.}, year = {2011}, language = {en} } @phdthesis{vonNicolai2011, author = {von Nicolai, Christina}, title = {The interplay of salt movements and regional tectonics at the passive continental margin of the South Atlantic, Kwanza Basin}, address = {Potsdam}, pages = {134 S.}, year = {2011}, language = {en} } @phdthesis{Blaser2011, author = {Blaser, Lilian}, title = {Bayesian networks for tsunami early warning}, address = {Potsdam}, pages = {127 S.}, year = {2011}, language = {en} } @phdthesis{MenesesRioseco2011, author = {Meneses Rioseco, Ernesto}, title = {Lithopheric rheology at the Dead Sea Transform Fault constrained by thermo-mechanical modeling}, address = {Potsdam}, pages = {154 S.}, year = {2011}, language = {en} } @phdthesis{Chapligin2011, author = {Chapligin, Bernhard}, title = {From method develoment to climate reconstruction - oxygen isotope analysis of biogenic silica from Lake El'gygytgyn, NE Siberia}, address = {Potsdam}, pages = {195 S.}, year = {2011}, language = {en} } @phdthesis{Meyer2011, author = {Meyer, Sven Walter Heinrich}, title = {Entwicklung und Erprobung von methodischen Grundlagen zur Konzipierung eines Entscheidungshilfesystems f{\"u}r die Begr{\"u}ndung von Extremstandorten}, address = {Potsdam}, pages = {279 S.}, year = {2011}, language = {de} } @phdthesis{Zhang2011, author = {Zhang, Zhuodong}, title = {A regional scale study of wind erosion in the Xilingele grassland based on computational fluid dynamics}, address = {Potsdam}, pages = {143 S.}, year = {2011}, language = {en} } @phdthesis{Fritz2011, author = {Fritz, Michael}, title = {Late quaternary environmental dynamics of the western canadian artic : permafrost and lake sediment archives at the easter beringian edge}, address = {Potsdam}, pages = {119 S.}, year = {2011}, language = {en} } @article{MorenoMelnickRosenauetal.2011, author = {Moreno, Marcelo Spegiorin and Melnick, Daniel and Rosenau, M. and Bolte, John and Klotz, Jan and Echtler, Helmut Peter and B{\´a}ez, Juan Carlos and Bataille, Klaus and Chen, J. and Bevis, M. and Hase, H. and Oncken, Onno}, title = {Heterogeneous plate locking in the South-Central Chile subduction zone building up the next great earthquake}, series = {Earth \& planetary science letters}, volume = {305}, journal = {Earth \& planetary science letters}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.03.025}, pages = {413 -- 424}, year = {2011}, abstract = {We use Global Positioning System (GPS) velocities and kinematic Finite Element models (FE-models) to infer the state of locking between the converging Nazca and South America plates in South-Central Chile (36 degrees S -46 degrees S) and to evaluate its spatial and temporal variability. GPS velocities provide information on earthquake-cycle deformation over the last decade in areas affected by the megathrust events of 1960 (M-w = 9.5) and 2010 (M-w = 8.8). Our data confirm that a change in surface velocity patterns of these two seismotectonic segments can be related to their different stages in the seismic cycle: Accordingly, the northern (2010) segment was in a final stage of interseismic loading whereas the southern (1960) segment is still in a postseismic stage and undergoes a prolonged viscoelastic mantle relaxation. After correcting the signals for mantle relaxation, the residual GPS velocity pattern suggests that the plate interface accumulates slip deficit in a spatially and presumably temporally variable way towards the next great event. Though some similarity exist between locking and 1960 coseismic slip, extrapolating the current, decadal scale slip deficit accumulation towards the similar to 300-yr recurrence times of giant events here does neither yield the slip distribution nor the moment magnitude of the 1960 earthquake. This suggests that either the locking pattern is evolving in time (to reconcile a slip deficit distribution similar to the 1960 earthquake) or that some asperities are not persistent over multiple events. The accumulated moment deficit since 1960 suggests that highly locked patches in the 1960 segment are already capable of producing a M similar to 8 event if triggered to fail by stress transfer from the 2010 event.}, language = {en} } @article{NeumannCoselZimmermannHalletal.2011, author = {Neumann-Cosel, Luisa and Zimmermann, Beate and Hall, Jefferson S. and van Breugel, Michiel and Elsenbeer, Helmut}, title = {Soil carbon dynamics under young tropical secondary forests on former pastures-A case study from Panama}, series = {Forest ecology and management}, volume = {261}, journal = {Forest ecology and management}, number = {10}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-1127}, doi = {10.1016/j.foreco.2010.07.023}, pages = {1625 -- 1633}, year = {2011}, abstract = {Secondary forests are gaining increased importance in tropical landscapes and have recently been reported to act as potential belowground carbon sinks. While economic interest in the management of secondary forests to mitigate carbon emissions is rising, the dynamics of soil carbon stocks under these ecosystems remain poorly understood. Recent studies report conflicting results concerning soil carbon trends as well as multiple confounding factors (e.g. soil type, topography and land-use history) affecting these trends. In this study, organic carbon stocks were measured in the mineral soil up to 20 cm depth of at 24 active pastures, 5-8-year-old, and 12-15-year-old secondary forest sites on former pastures. Additionally, we estimated carbon stocks under a 100-year-old secondary forest and compared them to those of nearby mature forests. Abiotic conditions in the study area were homogenous, enabling us to isolate the effect of land-use change on soil organic carbon stocks. Contrary to our expectations, soil carbon stocks in the top 10 cm did not change with young secondary forest development. Pasture soils stored 24.8 +/- 2.9 Mg ha(-1) carbon (mean +/- standard error) in the top 10 cm, and no accumulation of soil carbon was apparent during the first 15 years of secondary succession. Soil carbon stocks under 100-year-old secondary forests, averaging 43.0 +/- 7.9 Mg ha(-1) (mean +/- standard error), were clearly higher than those recorded at younger sites and approached levels of soil carbon stocks under mature forests. These data indicate that soil carbon stocks in this region of Panama are not affected by the land-use transition from pasture to young secondary regrowth. However, an increase of soil carbon storage might be possible over a longer period of time. Our results support trends observed in other tropical areas and highlight the importance of environmental conditions such as soil properties rather than land-use transitions on soil carbon dynamics. While our understanding of organic carbon dynamics in tropical soils remains limited, these results underscore the challenges of undertaking short-term reforestation projects with the expectation of increasing soil carbon sequestration.}, language = {en} } @article{EhlertFrankHaleyetal.2011, author = {Ehlert, C. and Frank, M. and Haley, B. A. and Boeniger, Urs and De Deckker, P. and Gingele, F. X.}, title = {Current transport versus continental inputs in the eastern Indian Ocean Radiogenic isotope signatures of clay size sediments}, series = {Geochemistry, geophysics, geosystems}, volume = {12}, journal = {Geochemistry, geophysics, geosystems}, number = {12}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1029/2011GC003544}, pages = {17}, year = {2011}, abstract = {Analyses of radiogenic neodymium (Nd), strontium (Sr), and lead (Pb) isotope compositions of clay-sized detrital sediments allow detailed tracing of source areas of sediment supply and present and past transport of particles by water masses in the eastern Indian Ocean. Isotope signatures in surface sediments range from -21.5 (epsilon Nd), 0.8299 ((87)Sr/(86S)r), and 19.89 ((206)Pb/(204)Pb) off northwest Australia to + 0.7 (epsilon Nd), 0.7069 ((87)Sr/(86)Sr), and 17.44 ((206)Pb/(204)Pb) southwest of Java. The radiogenic isotope signatures primarily reflect petrographic characteristics of the surrounding continental bedrocks but are also influenced by weathering-induced grain size effects of Pb and Sr isotope systems with superimposed features that are caused by current transport of clay-sized particles, as evidenced off Australia where a peculiar isotopic signature characterizes sediments underlying the southward flowing Leeuwin Current and the northward flowing West Australian Current (WAC). Gravity core FR10/95-GC17 off west Australia recorded a major isotopic change from Last Glacial Maximum values of -10 (epsilon Nd), 0.745 ((87S)r/(86)Sr), and 18.8 ((206)Pb/(204)Pb) to Holocene values of -22 (epsilon Nd), 0.8 ((87)Sr/(86)Sr), and 19.3 ((206)Pb/(204)Pb), which documents major climatically driven changes of the WAC and in local riverine particle supply from Australia during the past 20 kyr. In contrast, gravity core FR10/95-GC5 located below the present-day pathway of the Indonesian throughflow (ITF) shows a much smaller isotopic variability, indicating a relatively stable ITF hydrography over most of the past 92 kyr. Only the surface sediments differ significantly in their isotopic composition, indicating substantial changes in erosional sources attributed to a change of the current regime during the past 5 kyr.}, language = {en} } @article{HeistermannKneis2011, author = {Heistermann, Maik and Kneis, David}, title = {Benchmarking quantitative precipitation estimation by conceptual rainfall-runoff modeling}, series = {Water resources research}, volume = {47}, journal = {Water resources research}, number = {23}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0043-1397}, doi = {10.1029/2010WR009153}, pages = {23}, year = {2011}, abstract = {Hydrologic modelers often need to know which method of quantitative precipitation estimation (QPE) is best suited for a particular catchment. Traditionally, QPE methods are verified and benchmarked against independent rain gauge observations. However, the lack of spatial representativeness limits the value of such a procedure. Alternatively, one could drive a hydrological model with different QPE products and choose the one which best reproduces observed runoff. Unfortunately, the calibration of conceptual model parameters might conceal actual differences between the QPEs. To avoid such effects, we abandoned the idea of determining optimum parameter sets for all QPE being compared. Instead, we carry out a large number of runoff simulations, confronting each QPE with a common set of random parameters. By evaluating the goodness-of-fit of all simulations, we obtain information on whether the quality of competing QPE methods is significantly different. This knowledge is inferred exactly at the scale of interest-the catchment scale. We use synthetic data to investigate the ability of this procedure to distinguish a truly superior QPE from an inferior one. We find that the procedure is prone to failure in the case of linear systems. However, we show evidence that in realistic (nonlinear) settings, the method can provide useful results even in the presence of moderate errors in model structure and streamflow observations. In a real-world case study on a small mountainous catchment, we demonstrate the ability of the verification procedure to reveal additional insights as compared to a conventional cross validation approach.}, language = {en} } @article{WienhoeferLindenmaierZehe2011, author = {Wienh{\"o}fer, Jan and Lindenmaier, Falk and Zehe, Erwin}, title = {Challenges in understanding the hydrologic controls on the mobility of slow-moving landslides}, series = {Vadose zone journal}, volume = {10}, journal = {Vadose zone journal}, number = {2}, publisher = {Soil Science Society of America}, address = {Madison}, issn = {1539-1663}, doi = {10.2136/vzj2009.0182}, pages = {496 -- 511}, year = {2011}, abstract = {Slow-moving landslides are a wide-spread type of active mass movement, can cause severe damages to infrastructure, and may be a precursor of sudden catastrophic slope failures. Pore-water pressure is commonly regarded as the most important among a number of possible factors controlling landslide velocity. We used high-resolution monitoring data to explore the relations of landslide mobility and hydrologic processes at the Heumoser landslide in Austria, which is characterized by continuous slow movement along a shear zone. Movement rates showed a seasonality that was associated with elevated pore-water pressures. Pore pressure monitoring revealed a system of confined and separated aquifers with differing dynamics. Analysis of a simple infinite slope mobility model showed that small variations in parameters, along with measured pore pressure dynamics, provided a perfect match to our observations. Modeling showed a stabilizing effect of snow cover due to the additional load. This finding was supported by a multiple regression model, which further suggested that effective pore pressures at the slip surface were partially differing from the borehole observations and were related to preferential infiltration and subsurface flow in adjacent areas. It appears that in a setting like the Heumoser landslide, hydrologic processes delicately influence slope mobility through their control on pore pressure dynamics and the weight of the landslide body, which challenges observation and modeling. Moreover, it appears that their simplicity, and especially their high sensitivity to parameter variations, limits the conclusions that can be drawn from infinite slope models.}, language = {en} } @article{HasslerZimmermannvanBreugeletal.2011, author = {Haßler, Sibylle Kathrin and Zimmermann, Beate and van Breugel, Michiel and Hall, Jefferson S. and Elsenbeer, Helmut}, title = {Recovery of saturated hydraulic conductivity under secondary succession on former pasture in the humid tropics}, series = {Forest ecology and management}, volume = {261}, journal = {Forest ecology and management}, number = {10}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-1127}, doi = {10.1016/j.foreco.2010.06.031}, pages = {1634 -- 1642}, year = {2011}, abstract = {Landscapes in the humid tropics are undergoing a continuous change in land use. Deforestation is still taking its toll on forested areas, but at the same time more and more secondary forests emerge where formerly agricultural lands and pastures are being abandoned. Regarding soil hydrology, the extent to which secondary succession can recover soil hydrological properties disturbed by antecedent deforestation and pasture use is yet poorly understood. We investigated the effect of secondary succession on saturated hydraulic conductivity (Ks) at two soil depths (0-6 and 6-12 cm) using a space-for-time approach in a landscape mosaic in central Panama. The following four land-use classes were studied: pasture (P), secondary forest of 5-8 years of age (SF5), secondary forest of 12-15 years of age (SF12) and secondary forest of more than 100 years of age (SF100), each replicated altogether four times in different micro-catchments across the study region. The hydrological implications of differences in Ks in response to land-use change with land use, especially regarding overland flow generation, were assessed via comparisons with rainfall intensities. Recovery of Ks could be detected in the 0-6 cm depth after 12 years of secondary succession: P and SF5 held similar Ks values, but differed significantly (alpha = 0.05) from SF12 and SF100 which in turn were indistinguishable. Variability within the land cover classes was large but, due to sufficient replication in the study, Ks recovery could be detected nonetheless. Ks in the 6-12 cm depth did not show any differences between the land cover classes; only Ks of the uppermost soil layer was affected by land-use changes. Overland flow - as inferred from comparisons of Ks with rainfall intensities - is more likely on P and SF5 sites compared to SF12 and 5E100 for the upper sample depth; however, generally low values at the 6-12 cm depth are likely to impede vertical percolation during high rainfall intensities regardless of land use. We conclude that Ks can recover from pasture use under secondary succession up to pre-pasture levels, but the process may take more than 8 years. In order to gain comprehensive understanding of Ks change with land use and its hydrological implications, more studies with detailed land-use histories and combined measurements of Ks, overland flow, precipitation and throughfall are essential.}, language = {en} } @article{HothornMuellerSchroederetal.2011, author = {Hothorn, Torsten and M{\"u}ller, J{\"o}rg and Schroeder, Boris and Kneib, Thomas and Brandl, Roland}, title = {Decomposing environmental, spatial, and spatiotemporal components of species distributions}, series = {Ecological monographs : a publication of the Ecological Society of America.}, volume = {81}, journal = {Ecological monographs : a publication of the Ecological Society of America.}, number = {2}, publisher = {Wiley}, address = {Washington}, issn = {0012-9615}, doi = {10.1890/10-0602.1}, pages = {329 -- 347}, year = {2011}, abstract = {Species distribution models are an important tool to predict the impact of global change on species distributional ranges and community assemblages. Although considerable progress has been made in the statistical modeling during the last decade, many approaches still ignore important features of species distributions, such as nonlinearity and interactions between predictors, spatial autocorrelation, and nonstationarity, or at most incorporate only some of these features. Ecologists, however, require a modeling framework that simultaneously addresses all these features flexibly and consistently. Here we describe such an approach that allows the estimation of the global effects of environmental variables in addition to local components dealing with spatiotemporal autocorrelation as well as nonstationary effects. The local components can be used to infer unknown spatiotemporal processes; the global component describes how the species is influenced by the environment and can be used for predictions, allowing the fitting of many well-known regression relationships, ranging from simple linear models to complex decision trees or from additive models to models inspired by machine learning procedures. The reliability of spatiotemporal predictions can be qualitatively predicted by separately evaluating the importance of local and global effects. We demonstrate the potential of the new approach by modeling the breeding distribution of the Red Kite (Milvus milvus), a bird of prey occurring predominantly in Western Europe, based on presence/absence data from two mapping campaigns using grids of 40 km 2 in Bavaria. The global component of the model selected seven environmental variables extracted from the CORINE and WorldClim databases to predict Red Kite breeding. The effect of altitude was found to be nonstationary in space, and in addition, the data were spatially autocorrelated, which suggests that a species distribution model that does not allow for spatially varying effects and spatial autocorrelation would have ignored important processes determining the distribution of Red Kite breeding across Bavaria. Thus, predictions from standard species distribution models that do not allow for real-world complexities may be considerably erroneous. Our analysis of Red Kite breeding exemplifies the potential of the innovative approach for species distribution models. The method is also applicable to modeling count data.}, language = {en} } @article{LoprienoBousquetBucheretal.2011, author = {Loprieno, Andrea and Bousquet, Romain and Bucher, Stefan and Ceriani, Stefano and Dalla Torre, Florian H. and F{\"u}genschuh, Bernhard and Schmid, Stefan M.}, title = {The valais units in Savoy (France) a key area for understanding the palaeogeography and the tectonic evolution of the Western Alps}, series = {International journal of earth sciences}, volume = {100}, journal = {International journal of earth sciences}, number = {5}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-010-0595-1}, pages = {963 -- 992}, year = {2011}, abstract = {The Valais units in Savoy (Zone des BrSches de Tarentaise) have been re-mapped in great detail and are subject of combined stratigraphic, structural and petrological investigations summarized in this contribution. The sediments and rare relics of basement, together with Cretaceous age mafic and ultramafic rocks of the Valais palaeogeographical domain, represent the heavily deformed relics of the former distal European margin (External Valais units) and an ocean-continent transition (Internal Valais unit or Versoyen unit) that formed during rifting. This rifting led to the opening of the Valais ocean, a northern branch of the Alpine Tethys. Post-rift sediments referred to as "Valais trilogy" stratigraphically overlie both External and Internal Valais successions above an angular unconformity formed in Barremian to Aptian times, providing robust evidence for the timing of the opening of the Valais ocean. The Valais units in Savoy are part of a second and more external mid-Eocene high-pressure belt in the Alps that sutured the Brian double dagger onnais microcontinent to Europe. Top-N D1-deformation led to the formation of a nappe stack that emplaced the largely eclogite-facies Internal Valais unit (Versoyen) onto blueschist-facies External Valais units. The latter originally consisted of, from internal to external, the Petit St. Bernard unit, the Roc de l'Enfer unit, the MoA >> tiers unit and the Quermoz unit. Ongoing top-N D2-thrusting and folding substantially modified this nappe stack. Post 35 Ma D3 folding led to relatively minor modifications of the nappe stack within the Valais units but was associated with substantial top-WNW thrusting of the Valais units over the Dauphinois units along the Roselend thrust during W-directed indentation of the Adria block contributing to the formation of the arc of the Western Alps.}, language = {en} } @article{WiederkehrBousquetZiemannetal.2011, author = {Wiederkehr, Michael and Bousquet, Romain and Ziemann, Martin Andreas and Berger, Alfons and Schmid, Stefan M.}, title = {3-D assessment of peak-metamorphic conditions by Raman spectroscopy of carbonaceous material an example from the margin of the Lepontine dome (Swiss Central Alps)}, series = {International journal of earth sciences}, volume = {100}, journal = {International journal of earth sciences}, number = {5}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-010-0622-2}, pages = {1029 -- 1063}, year = {2011}, abstract = {This study monitors regional changes in the crystallinity of carbonaceous matter (CM) by applying Micro-Raman spectroscopy to a total of 214 metasediment samples (largely so-called Bundnerschiefer) dominantly metamorphosed under blueschist- to amphibolite-facies conditions. They were collected within the northeastern margin of the Lepontine dome and easterly adjacent areas of the Swiss Central Alps. Three-dimensional mapping of isotemperature contours in map and profile views shows that the isotemperature contours associated with the Miocene Barrow-type Lepontine metamorphic event cut across refolded nappe contacts, both along and across strike within the northeastern margin of the Lepontine dome and adjacent areas. Further to the northeast, the isotemperature contours reflect temperatures reached during the Late Eocene subduction-related blueschist-facies event and/or during subsequent near-isothermal decompression; these contours appear folded by younger, large-scale post-nappe-stacking folds. A substantial jump in the recorded maximum temperatures across the tectonic contact between the frontal Adula nappe complex and surrounding metasediments indicates that this contact accommodated differential tectonic movement of the Adula nappe with respect to the enveloping Bundnerschiefer after maximum temperatures were reached within the northern Adula nappe, i.e. after Late Eocene time.}, language = {en} } @article{SteinhoefelBreuervonBlanckenburgetal.2011, author = {Steinhoefel, Grit and Breuer, J{\"o}rn and von Blanckenburg, Friedhelm and Horn, Ingo and Kaczorek, Danuta and Sommer, Michael}, title = {Micrometer silicon isotope diagnostics of soils by UV femtosecond laser ablation}, series = {Chemical geology : official journal of the European Association for Geochemistry}, volume = {286}, journal = {Chemical geology : official journal of the European Association for Geochemistry}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0009-2541}, doi = {10.1016/j.chemgeo.2011.05.013}, pages = {280 -- 289}, year = {2011}, abstract = {This study presents the first Si isotope data of the principle Si pools in soils determined by a UV femtosecond laser ablation system coupled to a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). This method reveals accurate and precise Si isotope data on bulk materials, and at high spatial resolution, on the mineral scale. The following Si pools have been investigated: a) the Si source to soils on all major silicate minerals on thin sections from bedrock fragments in the soil profiles; b) bulk soils (particle size <2 mm) after fusion to glass beads with an iridium-strip heater or pressed into powder pellets: c) separated clay fractions as pressed powder pellets and e) separated phytoliths as pressed powder pellets. Multiple analyses of three rock standards, BHVO-2, AGV-1 and RGM-1 as fused glass beads and as pressed powder pellets, reveal delta(30)Si values within the expected range of igneous rocks. The MPI-DING reference glass KL2-G exhibits the same Si isotope composition after remelting by an iridium-strip heater showing that this technique does not alter the isotope composition of the glass. We used this approach to investigated two immature Cambisols developed on sandstone and paragneiss in the Black Forest (Germany), respectively. Bulk soils show a largely uniform Si isotope signature for different horizons and locations, which is close to those of primary quartz and feldspar with delta(30)Si values around -0.4 parts per thousand. Soil clay formation is associated with limited Si mobility, which preserves initial Si isotope signatures of parental minerals. An exception is the organic horizon of the paragneiss catchment where intense weathering leads to a high mobility of Si and significant negative isotope signatures as low as to -1.00 parts per thousand in bulk soils. Biogenic opal in the form of phytoliths, exhibits negative Si isotope signatures of about -0.4 parts per thousand. These results demonstrate that UV femtosecond laser ablation MC-ICP-MS provides a tool to characterize the Si isotope signature of the principle Si pools left behind after weathering and Si transport have altered soils. These results can now serve as a fingerprint of the residual solids that can be used to explain the isotope composition of dissolved Si in soil solutions and river water, which is mostly enriched in the heavy isotopes.}, language = {en} } @article{RomeroVianaJuliaSchimmeletal.2011, author = {Romero-Viana, Lidia and Julia, Ramon and Schimmel, Martin and Camacho, Antonio and Vicente, Eduardo and Rosa Miracle, M.}, title = {Reconstruction of annual winter rainfall since AD1579 in central-eastern Spain based on calcite laminated sediment from Lake La Cruz}, series = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change}, volume = {107}, journal = {Climatic change : an interdisciplinary, intern. journal devoted to the description, causes and implications of climatic change}, number = {3-4}, publisher = {Springer}, address = {Dordrecht}, issn = {0165-0009}, doi = {10.1007/s10584-010-9966-7}, pages = {343 -- 361}, year = {2011}, abstract = {We present the first winter (December to March) rainfall reconstruction based in a novel proxy, the thickness of annual calcite laminations preserved in Lake La Cruz (central-eastern Spain). A previous calibration analysis between laminae thickness and the instrumental data series (1950 to present) indicated a highly significant correlation with winter rainfall. Therefore this study attempts the winter rainfall reconstruction since the onset of laminations (1579 a.d.) by means of the calibration function previously developed. The verification analysis between inferred annual values and earlier instrumental data (1859-1949) confirms the suitability of this novel proxy and the reliability of the series reconstructed. The reconstructed series show the fluctuating character of winter rainfall in the western Mediterranean area; interdecadal dry periods alternated with wetter periods following, in a board sense, the pattern recorded by documentary sources in other regions of the Iberian Peninsula. At present times regional winter rainfall anomalies are highly correlated with the phase of the North Atlantic Oscillation (NAO). However the time series analysis showed the dominance of nonstationary components at high frequencies of the climate signal over the last four centuries suggesting that the connection between winter rainfall and the NAO has not been stable over time and also other modes of variability, not only NAO, may have conditioned winter rainfall variability.}, language = {en} } @article{Endrun2011, author = {Endrun, Brigitte}, title = {Love wave contribution to the ambient vibration H/V amplitude peak observed with array measurements}, series = {Journal of seismology}, volume = {15}, journal = {Journal of seismology}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {1383-4649}, doi = {10.1007/s10950-010-9191-x}, pages = {443 -- 472}, year = {2011}, abstract = {This study applies array methods to measure the relative proportions of Love and Rayleigh waves in the ambient vibration wavefield. Information on these properties is of special relevance for frequencies around the horizontal-to-vertical (H/V) spectral amplitude ratio peak. The analysis of H/V curves, a popular technique in site characterisation, commonly assumes that the curves represent the frequency-dependent Rayleigh wave ellipticity. For the detailed interpretation of amplitudes or the inversion of the curves, it is therefore necessary to estimate and correct for the contribution of other wave types to the ambient vibration wavefield. I use available ambient vibration array measurements to determine the relative amount of Love and Rayleigh waves on the horizontal components by frequency-dependent analysis of the main propagation and polarisation directions, with a special emphasis on the H/V peak frequency as determined from the same recordings. Tests with synthetic data demonstrate the feasibility of this approach, at least in the presence of dominant source regions. Analysis of the data from 12 measurements at nine European sites, which include shallow as well as deep locations that span a wide range of impedance contrasts at the sediment-bedrock interface, indicates that the relative contribution of Rayleigh waves varies widely with frequency, from close to 0\% to more than 70\%. While most data sets show relative Rayleigh wave contributions between 40\% and 50\% around the H/V peak, there are also examples where Love waves clearly dominate the wavefield at the H/V peak, even for a site with a low impedance contrast. Longer-term measurements at one site indicate temporal variations in the relative Rayleigh wave content between day- and nighttime. Results calculated with the method introduced herein generally compare well with results of modified spatial autocorrelation analysis. These two methods might be used in a complimentary fashion, as both rely on different properties of the ambient vibration wavefield. This study illustrates that it is possible to measure the relative Rayleigh wave content of the noise wavefield from array data. Furthermore, the examples presented herein indicate it is important to estimate this property, as the assumption that there are an equal proportion of Love and Rayleigh waves is not always correct.}, language = {en} } @article{GeversHoyeToppingetal.2011, author = {Gevers, Jana and Hoye, Toke Thomas and Topping, Chris John and Glemnitz, Michael and Schroeder, Boris}, title = {Biodiversity and the mitigation of climate change through bioenergy impacts of increased maize cultivation on farmland wildlife}, series = {Global change biology : Bioenergy}, volume = {3}, journal = {Global change biology : Bioenergy}, number = {6}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1757-1693}, doi = {10.1111/j.1757-1707.2011.01104.x}, pages = {472 -- 482}, year = {2011}, abstract = {The public promotion of renewable energies is expected to increase the number of biogas plants and stimulate energy crops cultivation (e. g. maize) in Germany. In order to assess the indirect effects of the resulting land-use changes on biodiversity, we developed six land-use scenarios and simulated the responses of six farmland wildlife species with the spatially explicit agent-based model system ALMaSS. The scenarios differed in composition and spatial configuration of arable crops. We implemented scenarios where maize for energy production replaced 15\% and 30\% of the area covered by other cash crops. Biogas maize farms were either randomly distributed or located within small or large aggregation clusters. The animal species investigated were skylark (Alauda arvensis), grey partridge (Perdix perdix), European brown hare (Lepus europaeus), field vole (Microtus agrestis), a linyphiid spider (Erigone atra) and a carabid beetle (Bembidion lampros). The changes in crop composition had a negative effect on the population sizes of skylark, partridge and hare and a positive effect on the population sizes of spider and beetle and no effect on the population size of vole. An aggregated cultivation of maize amplified these effects for skylark. Species responses to changes in the crop composition were consistent across three differently structured landscapes. Our work suggests that with the compliance to some recommendations, negative effects of biogas-related land-use change on the populations of the six representative farmland species can largely be avoided.}, language = {en} } @article{BoixFrijiaVicedoetal.2011, author = {Boix, Carme and Frijia, Gianluca and Vicedo, Vicent and Bernaus, Josep M. and Di Lucia, Matteo and Parente, Mariano and Caus, Esmeralda}, title = {Larger foraminifera distribution and strontium isotope stratigraphy of the La Cova limestones (Coniacian-Santonian, "Serra del Montsec", Pyrenees, NE Spain)}, series = {Cretaceous research}, volume = {32}, journal = {Cretaceous research}, number = {6}, publisher = {Elsevier}, address = {London}, issn = {0195-6671}, doi = {10.1016/j.cretres.2011.05.009}, pages = {806 -- 822}, year = {2011}, abstract = {The Upper Cretaceous La Cova limestones (southern Pyrenees, Spain) host a rich and diverse larger foraminiferal fauna, which represents the first diversification of K-strategists after the mass extinction at the Cenomanian-Turonian boundary. The stratigraphic distribution of the main taxa of larger foraminifera defines two assemblages. The first assemblage is characterised by the first appearance of lacazinids (Pseudolacazina loeblichi) and mean-dropsinids (Eofallotia simplex), by the large agglutinated Montsechiana montsechiensis, and by several species of complex rotalids (Rotorbinella campaniola, Iberorotalia reicheli, Orbitokhatina wondersmitti and Calcarinella schaubi). The second assemblage is defined by the appearance of Lacazina pyrenaica, Palandrosina taxyae and Martiguesia cyclamminiformis. A late Coniacian-early Santonian age was so far accepted for the La Cova limestones, based on indirect correlation with deep-water fades bearing planktic foraminifers of the Dicarinella concavata zone. Strontium isotope stratigraphy, based on many samples of pristine biotic calcite of rudists and ostreids, indicates that the La Cova limestones span from the early Coniacian to the early-middle Santonian boundary. The first assemblage of larger foraminifera appears very close to the early-middle Coniacian boundary and reaches its full diversity by the middle Coniacian. The originations defining the second assemblage are dated as earliest Santonian: they represent important bioevents to define the Coniacian-Santonian boundary in the shallow-water facies of the South Pyrenean province. By means of the calibration of strontium isotope stratigraphy to the Geological Time Scale, the larger foraminiferal assemblages of the La Cova limestones can be correlated to the standard biozonal scheme of ammonites, planktonic foraminifers and calcareous nannoplankton. This correlation is a first step toward a larger foraminifera standard biozonation for Upper Cretaceous carbonate platform facies.}, language = {en} } @article{MunzKrauseTecklenburgetal.2011, author = {Munz, Matthias and Krause, Stefan and Tecklenburg, Christina and Binley, Andrew}, title = {Reducing monitoring gaps at the aquifer-river interface by modelling groundwater-surface water exchange flow patterns}, series = {Hydrological processes}, volume = {25}, journal = {Hydrological processes}, number = {23}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0885-6087}, doi = {10.1002/hyp.8080}, pages = {3547 -- 3562}, year = {2011}, abstract = {This study investigates spatial patterns and temporal dynamics of aquifer-river exchange flow at a reach of the River Leith, UK. Observations of sub-channel vertical hydraulic gradients at the field site indicate the dominance of groundwater up-welling into the river and the absence of groundwater recharge from surface water. However, observed hydraulic heads do not provide information on potential surface water infiltration into the top 0-15 cm of the streambed as these depths are not covered by the existing experimental infrastructure. In order to evaluate whether surface water infiltration is likely to occur outside the 'window of detection', i.e. the shallow streambed, a numerical groundwater model is used to simulate hydrological exchanges between the aquifer and the river. Transient simulations of the successfully validated model (Nash and Sutcliff efficiency of 0.91) suggest that surface water infiltration is marginal and that the possibility of significant volumes of surface water infiltrating into non-monitored shallow streambed sediments can be excluded for the simulation period. Furthermore, the simulation results show that with increasing head differences between river and aquifer towards the end of the simulation period, the impact of streambed topography and hydraulic conductivity on spatial patterns of exchange flow rates decreases. A set of peak flow scenarios with altered groundwater-surface water head gradients is simulated in order to quantify the potential for surface water infiltration during characteristic winter flow conditions following the observation period. The results indicate that, particularly at the beginning of peak flow conditions, head gradients are likely to cause substantial increase in surface water infiltration into the streambed. The study highlights the potential for the improvement of process understanding of hyporheic exchange flow patterns at the stream reach scale by simulating aquifer-river exchange fluxes with a standard numerical groundwater model and a simple but robust model structure and parameterization. Copyright}, language = {en} } @article{HaneyKummerowLangenbruchetal.2011, author = {Haney, Frank and Kummerow, J. and Langenbruch, C. and Dinske, C. and Shapiro, Serge A. and Scherbaum, Frank}, title = {Magnitude estimation for microseismicity induced during the KTB 2004/2005 injection experiment}, series = {Geophysics}, volume = {76}, journal = {Geophysics}, number = {6}, publisher = {Society of Exploration Geophysicists}, address = {Tulsa}, issn = {0016-8033}, doi = {10.1190/GEO2011-0020.1}, pages = {WC47 -- WC53}, year = {2011}, abstract = {We determined the magnitudes of 2540 microseismic events measured at one single 3C borehole geophone at the German Deep Drilling Site (known by the German acronym, KTB) during the injection phase 2004/2005. For this task we developed a three-step approach. First, we estimated local magnitudes of 104 larger events with a standard method based on amplitude measurements at near-surface stations. Second, we investigated a series of parameters to characterize the size of these events using the seismograms of the borehole sensor, and we compared them statistically with the local magnitudes. Third, we extrapolated the regression curve to obtain the magnitudes of 2436 events that were only measured at the borehole geophone. This method improved the magnitude of completeness for the KTB data set by more than one order down to M = -2.75. The resulting b-value for all events was 0.78, which is similar to the b-value obtained from taking only the greater events with standard local magnitude estimation from near-surface stations, b = 0.86. The more complete magnitude catalog was required to study the magnitude distribution with time and to characterize the seismotectonic state of the KTB injection site. The event distribution with time was consistent with prediction from theory assuming pore pressure diffusion as the underlying mechanism to trigger the events. The value we obtained for the seismogenic index of -4 suggested that the seismic hazard potential at the KTB site is comparatively low.}, language = {en} } @article{SchmelzbachScherbaumTronickeetal.2011, author = {Schmelzbach, C. and Scherbaum, Frank and Tronicke, Jens and Dietrich, P.}, title = {Bayesian frequency-domain blind deconvolution of ground-penetrating radar data}, series = {Journal of applied geophysics}, volume = {75}, journal = {Journal of applied geophysics}, number = {4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0926-9851}, doi = {10.1016/j.jappgeo.2011.08.010}, pages = {615 -- 630}, year = {2011}, abstract = {Enhancing the resolution and accuracy of surface ground-penetrating radar (GPR) reflection data by inverse filtering to recover a zero-phased band-limited reflectivity image requires a deconvolution technique that takes the mixed-phase character of the embedded wavelet into account. In contrast, standard stochastic deconvolution techniques assume that the wavelet is minimum phase and, hence, often meet with limited success when applied to GPR data. We present a new general-purpose blind deconvolution algorithm for mixed-phase wavelet estimation and deconvolution that (1) uses the parametrization of a mixed-phase wavelet as the convolution of the wavelet's minimum-phase equivalent with a dispersive all-pass filter, (2) includes prior information about the wavelet to be estimated in a Bayesian framework, and (3) relies on the assumption of a sparse reflectivity. Solving the normal equations using the data autocorrelation function provides an inverse filter that optimally removes the minimum-phase equivalent of the wavelet from the data, which leaves traces with a balanced amplitude spectrum but distorted phase. To compensate for the remaining phase errors, we invert in the frequency domain for an all-pass filter thereby taking advantage of the fact that the action of the all-pass filter is exclusively contained in its phase spectrum. A key element of our algorithm and a novelty in blind deconvolution is the inclusion of prior information that allows resolving ambiguities in polarity and timing that cannot be resolved using the sparseness measure alone. We employ a global inversion approach for non-linear optimization to find the all-pass filter phase values for each signal frequency. We tested the robustness and reliability of our algorithm on synthetic data with different wavelets, 1-D reflectivity models of different complexity, varying levels of added noise, and different types of prior information. When applied to realistic synthetic 2-D data and 2-D field data, we obtain images with increased temporal resolution compared to the results of standard processing.}, language = {en} } @article{SotoBaeuerleArriagadaGonzalezCastroCorreaetal.2011, author = {Soto Baeuerle, Maria Victoria and Arriagada Gonzalez, Joselyn and Castro Correa, Carmen Paz and Maerker, Michael and Rodolfi, Giuliano}, title = {Relationship between the change in land use in the Aconcagua basin and its correlative sandy coastal. Central Chile}, series = {Revista de geograf{\´i}a Norte Grande}, journal = {Revista de geograf{\´i}a Norte Grande}, number = {50}, publisher = {Instituto de Geograf{\´i}a, Pontificia Universidad Cat{\´o}lica de Chile}, address = {Santiago}, issn = {0718-3402}, pages = {187 -- 202}, year = {2011}, abstract = {In the Aconcagua basin the modernization and intensification of land use have resulted both in an agricultural conversion, and the increase in area cultivated. This process has been very intense as far that have entered new areas beyond the limits of the valley and towards sloping ground. This signals changes in land use over the vegetation coverage models. The analysis of the geomorphology of the coastline in detail, accounts for the occurrence of transformations on the beach and dunes that are spatially less significant, but evolutionarily important, since they show a sediment feeding, which could be correlated with changes in vegetation cover in the basin}, language = {es} } @unpublished{WellsteinSchroederEsselbachReinekingetal.2011, author = {Wellstein, Camilla and Schr{\"o}der-Esselbach, Boris and Reineking, Bjoern and Zimmermann, Niklaus E.}, title = {Understanding species and community response to environmental change - A functional trait perspective}, series = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, volume = {145}, journal = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8809}, doi = {10.1016/j.agee.2011.06.024}, pages = {1 -- 4}, year = {2011}, language = {en} } @article{LoefflerAnschlagBakeretal.2011, author = {Loeffler, J{\"o}rg and Anschlag, Kerstin and Baker, Barry and Finch, Oliver-D. and Diekkrueger, Bernd and Wundram, Dirk and Schroeder, Boris and Pape, Roland and Lundberg, Anders}, title = {Mountain ecosystem response to global change}, series = {Erdkunde : archive for scientific geography}, volume = {65}, journal = {Erdkunde : archive for scientific geography}, number = {2}, publisher = {Geographisches Inst., Univ. Bonn}, address = {Goch}, issn = {0014-0015}, doi = {10.3112/erdkunde.2011.02.06}, pages = {189 -- 213}, year = {2011}, abstract = {Mountain ecosystems are commonly regarded as being highly sensitive to global change. Due to the system complexity and multifaceted interacting drivers, however, understanding current responses and predicting future changes in these ecosystems is extremely difficult. We aim to discuss potential effects of global change on mountain ecosystems and give examples of the underlying response mechanisms as they are understood at present. Based on the development of scientific global change research in mountains and its recent structures, we identify future research needs, highlighting the major lack and the importance of integrated studies that implement multi-factor, multi-method, multi-scale, and interdisciplinary research.}, language = {en} } @article{HiemerScherbaumRoessleretal.2011, author = {Hiemer, Stefan and Scherbaum, Frank and R{\"o}ßler, Dirk and K{\"u}hn, Nicolas}, title = {Determination of tau(0) and Rock Site kappa from Records of the 2008/2009 Earthquake Swarm in Western Bohemia}, series = {Seismological research letters}, volume = {82}, journal = {Seismological research letters}, number = {3}, publisher = {Seismological Society of America}, address = {El Cerrito}, issn = {0895-0695}, doi = {10.1785/gssrl.82.3.387}, pages = {387 -- 393}, year = {2011}, language = {en} } @article{MuellerKoszinskiBrenningetal.2011, author = {Mueller, Marina Elsa Herta and Koszinski, Sylvia and Brenning, Alexander and Verch, Gernot and Korn, Ulrike and Sommer, Michael}, title = {Within-field variation of mycotoxin contamination of winter wheat is related to indicators of soil moisture}, series = {Plant and soil}, volume = {342}, journal = {Plant and soil}, number = {1-2}, publisher = {Springer}, address = {Dordrecht}, issn = {0032-079X}, doi = {10.1007/s11104-010-0695-5}, pages = {289 -- 300}, year = {2011}, abstract = {Humidity is an important determinant of the mycotoxin production (DON, ZEA) by Fusarium species in the grain ears. From a landscape perspective humidity is not evenly distributed across fields. The topographically-controlled redistribution of water within a single field rather leads to spatially heterogeneous soil water content and air humidity. Therefore we hypothesized that the spatial distribution of mycotoxins is related to these topographically-controlled factors. To test this hypothesis we studied the mycotoxin concentrations at contrasting topographic relief positions, i.e. hilltops and depressions characterized by soils of different soil moisture regimes, on ten winter wheat fields in 2006 and 2007. Maize was the preceding crop and minimum tillage was practiced in the fields. The different topographic positions were associated with moderate differences in DON and ZEA concentrations in 2006, but with significant differences in 2007, with six times higher median ZEA and two times higher median DON detected at depression sites compared to the hilltops. The depression sites correspond to a higher topographic wetness index as well as redoximorphic properties in soil profiles, which empirically supports our hypothesis at least for years showing wetter conditions in sensitive time windows for Fusarium infections.}, language = {en} } @article{HayhoeNeillPorderetal.2011, author = {Hayhoe, Shelby J. and Neill, Christopher and Porder, Stephen and McHorney, Richard and Lefebvre, Paul and Coe, Michael T. and Elsenbeer, Helmut and Krusche, Alex V.}, title = {Conversion to soy on the Amazonian agricultural frontier increases streamflow without affecting stormflow dynamics}, series = {Global change biology}, volume = {17}, journal = {Global change biology}, number = {5}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1354-1013}, doi = {10.1111/j.1365-2486.2011.02392.x}, pages = {1821 -- 1833}, year = {2011}, abstract = {Large-scale soy agriculture in the southern Brazilian Amazon now rivals deforestation for pasture as the region's predominant form of land use change. Such landscape-level change can have substantial consequences for local and regional hydrology, but these effects remain relatively unstudied in this ecologically and economically important region. We examined how the conversion to soy agriculture influences water balances and stormflows using stream discharge (water yields) and the timing of discharge (stream hydrographs) in small (2.5-13.5 km2) forested and soy headwater watersheds in the Upper Xingu Watershed in the state of Mato Grosso, Brazil. We monitored water yield for 1 year in three forested and four soy watersheds. Mean daily water yields were approximately four times higher in soy than forested watersheds, and soy watersheds showed greater seasonal variability in discharge. The contribution of stormflows to annual streamflow in all streams was low (< 13\% of annual streamflow), and the contribution of stormflow to streamflow did not differ between land uses. If the increases in water yield observed in this study are typical, landscape-scale conversion to soy substantially alters water-balance, potentially altering the regional hydrology over large areas of the southern Amazon.}, language = {en} } @article{VicedoFrijiaParenteetal.2011, author = {Vicedo, Vicent and Frijia, Gianluca and Parente, Mariano and Caus, Esmeralda}, title = {The late creataceous genera cuvillierinella, cyclopseudedomia, andrhapydionina (Rhapydioninidae, Foraminiferida) in shallow-watercarbonates of pylos (Peloponnese, Greece)}, series = {Journal of foraminiferal research}, volume = {41}, journal = {Journal of foraminiferal research}, number = {2}, publisher = {GeoScienceWorld}, address = {Cambridge}, issn = {0096-1191}, pages = {167 -- 181}, year = {2011}, abstract = {Shell architectures of the larger foraminiferal genera cyclopseudedomia, and Rhapydionina were studied by comparing topotypes of previously described species with new specimens retrieved from Late Cretaceous shallow-water carbonates of Pylos (Peloponnese, Greece), where the three genera are found in association. The megalospheric generation of each genus exhibits a distinctive shell shape in adult specimens (i.e., fan-shaped in Cyclopseudedomia, conical in Rhapydionina, and cylindrical in Cuvillierinella). Although their microspheric adults are similarly thin, flat, and discoidal, they can be identified at the genus level by means of a detailed structural analysis. Cavillierinella shows the septula to be interrupted by a large preseptal space, while Cyclopseudedomia and Rhapydionina exhibit continuous, non-interrupted septula. In addition, Cyclopseudedomia presents only one row of medullar chamberlets, whereas Rhapydionina shows numerous medullar chamberlets distributed in a thick basal layer. Two new species, Cuvillierinella pylosensis and Rhapydionina fleuryi, are described. The former is a more complex taxon than the type species, C salentina, while the latter corresponds to a more primitive species, R. liburnica. Strontium-isotope stratigraphy indicates an uppermost Campanian-lowermost Maastrichtian age for these new species.}, language = {en} } @article{RouxMoorkampJonesetal.2011, author = {Roux, E. and Moorkamp, Max and Jones, Alan G. and Bischoff, Monika and Endrun, Brigitte and Lebedev, Sergei and Meier, Thomas}, title = {Joint inversion of long-period magnetotelluric data and surface-wave dispersion curves for anisotropic structure application to data from Central Germany}, series = {Geophysical research letters}, volume = {38}, journal = {Geophysical research letters}, number = {3}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2010GL046358}, pages = {5}, year = {2011}, abstract = {Geophysical datasets sensitive to different physical parameters can be used to improve resolution of Earth's internal structure. Herein, we jointly invert long-period magnetotelluric (MT) data and surface-wave dispersion curves. Our approach is based on a joint inversion using a genetic algorithm for a one-dimensional (1-D) isotropic structure, which we extend to 1-D anisotropic media. We apply our new anisotropic joint inversion to datasets from Central Germany demonstrating the capacity of our joint inversion algorithm to establish a 1-D anisotropic model that fits MT and seismic datasets simultaneously and providing new information regarding the deep structure in Central Germany. The lithosphere/asthenosphere boundary is found at approx. 84 km depth and two main anisotropic layers with coincident most conductive/seismic fast-axis direction are resolved at lower crustal and asthenospheric depths. We also quantify the amount of seismic and electrical anisotropy in the asthenosphere showing an emerging agreement between the two anisotropic coefficients.}, language = {en} } @article{BartholdTyrallaSchneideretal.2011, author = {Barthold, Frauke Katrin and Tyralla, Christoph and Schneider, Katrin and Vache, Kellie B. and Frede, Hans-Georg and Breuer, Lutz}, title = {How many tracers do we need for end member mixing analysis (EMMA)? - a sensitivity analysis}, series = {Water resources research}, volume = {47}, journal = {Water resources research}, number = {7360}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0043-1397}, doi = {10.1029/2011WR010604}, pages = {14}, year = {2011}, abstract = {End member mixing analysis (EMMA) is a commonly applied method to identify and quantify the dominant runoff producing sources of water. It employs tracers to determine the dimensionality of the hydrologic system. Many EMMA studies have been conducted using two to six tracers, with some of the main tracers being Ca, Na, Cl(-), water isotopes, and alkalinity. Few studies use larger tracer sets including minor trace elements such as Li, Rb, Sr, and Ba. None of the studies has addressed the question of the tracer set size and composition, despite the fact that these determine which and how many end members (EM) will be identified. We examine how tracer set size and composition affects the conceptual model that results from an EMMA. We developed an automatic procedure that conducts EMMA while iteratively changing tracer set size and composition. We used a set of 14 tracers and 9 EMs. The validity of the resulting conceptual models was investigated under the aspects of dimensionality, EM combinations, and contributions to stream water. From the 16,369 possibilities, 23 delivered plausible results. The resulting conceptual models are highly sensitive to the tracer set size and composition. The moderate reproducibility of EM contributions indicates a still missing EM. It also emphasizes that the major elements are not always the most useful tracers and that larger tracer sets have an enhanced capacity to avoid false conclusions about catchment functioning. The presented approach produces results that may not be apparent from the traditional approach and it is a first step to add the idea of statistical significance to the EMMA approach.}, language = {en} } @article{MartinezGarciaRosellMeleJaccardetal.2011, author = {Martinez-Garcia, Alfredo and Rosell-Mele, Antoni and Jaccard, Samuel L. and Geibert, Walter and Sigman, Daniel M. and Haug, Gerald H.}, title = {Southern Ocean dust-climate coupling over the past four million years}, series = {Nature : the international weekly journal of science}, volume = {476}, journal = {Nature : the international weekly journal of science}, number = {7360}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/nature10310}, pages = {312 -- U141}, year = {2011}, abstract = {Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean(1,2). Indeed, dust supply to the Southern Ocean increases during ice ages, and 'iron fertilization' of the subantarctic zone may have contributed up to 40 parts per million by volume (p. p. m. v.) of the decrease (80-100 p. p. m. v.) in atmospheric carbon dioxide observed during late Pleistocene glacial cycles(3-7). So far, however, the magnitude of Southern Ocean dust deposition in earlier times and its role in the development and evolution of Pleistocene glacial cycles have remained unclear. Here we report a high-resolution record of dust and iron supply to the Southern Ocean over the past four million years, derived from the analysis of marine sediments from ODP Site 1090, located in the Atlantic sector of the subantarctic zone. The close correspondence of our dust and iron deposition records with Antarctic ice core reconstructions of dust flux covering the past 800,000 years (refs 8, 9) indicates that both of these archives record large-scale deposition changes that should apply to most of the Southern Ocean, validating previous interpretations of the ice core data. The extension of the record beyond the interval covered by the Antarctic ice cores reveals that, in contrast to the relatively gradual intensification of glacial cycles over the past three million years, Southern Ocean dust and iron flux rose sharply at the Mid-Pleistocene climatic transition around 1.25 million years ago. This finding complements previous observations over late Pleistocene glacial cycles(5,8,9), providing new evidence of a tight connection between high dust input to the Southern Ocean and the emergence of the deep glaciations that characterize the past one million years of Earth history.}, language = {en} } @article{NassvanGasseltJaumannetal.2011, author = {Nass, Andrea and van Gasselt, S. and Jaumann, Ralf and Asche, Hartmut}, title = {Implementation of cartographic symbols for planetary mapping in geographic information systems}, series = {Planetary and space science}, volume = {59}, journal = {Planetary and space science}, number = {11-12}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2010.08.022}, pages = {1255 -- 1264}, year = {2011}, abstract = {The steadily growing international interest in the exploration of planets in our Solar System and many advances in the development of space-sensor technology have led to the launch of a multitude of planetary missions to Mercury, Venus, the Earth's moon, Mars and various Outer-Solar System objects, such as the Jovian and Saturnian satellites. Camera instruments carried along on these missions image surfaces in different wavelength ranges and under different viewing angles, permitting additional data to be derived, such as spectral data or digital terrain models. Such data enable researchers to explore and investigate the development of planetary surfaces by analyzing and interpreting the inventory of surface units and structures. Results of such work are commonly abstracted and represented in thematic, mostly geological and geomorphological, maps. In order to facilitate efficient collaboration among different planetary research disciplines, mapping results need to be prepared, described, managed, archived, and visualized in a uniform way. These tasks have been increasingly carried out by means of computer-based geographic information systems (GIS or Cl systems) which have come to be widely employed in the field of planetary research since the last two decades. In this paper we focus on the simplification of mapping processes, putting specific emphasis on a cartographically correct visualization of planetary mapping data using GIS-based environments. We present and discuss the implementation of a set of standardized cartographic symbols for planetary mapping based on the Digital Cartographic Standard for Geologic Map Symbolization as prepared by the United States Geological Survey (USGS) for the Federal Geographic Data Committee (FGDC). Furthermore, we discuss various options to integrate this symbol catalog into generic GI systems, and more specifically into the Environmental Systems Research Institute's (ESRI) ArcGIS environment, and focus on requirements for symbol definitions in the field of planetary mapping. A symbology of this type can be embedded into any modular GIS environment capable in dealing with external stand-alone as well as database-driven management of symbol sets. Using such a uniform GIS-based symbol catalog will give the research community access to map results already cartographically elaborated, enabling them to create digital maps as a secondary data source in subsequent studies.}, language = {en} } @article{WeberCardonaValenciaetal.2011, author = {Weber, Marion and Cardona, A. and Valencia, V. and Altenberger, Uwe and Lopez-Martinez, M. and Tobon, M. and Zapata, Sebastian Henao and Zapata, G. and Concha, A. E.}, title = {Geochemistry and geochronology of the Guajira Eclogites, northern Colombia evidence of a metamorphosed primitive Cretaceous Caribbean Island-arc}, series = {Geologica acta}, volume = {9}, journal = {Geologica acta}, number = {3-4}, publisher = {Facultat de Geologia, Divisio III, Ci{\`e}ncies Experimentals i Matem{\`a}tiques, Universitat de Barcelona}, address = {Barcelona}, issn = {1695-6133}, doi = {10.1344/105.000001740}, pages = {425 -- 443}, year = {2011}, abstract = {The chemical composition of eclogites, found as boulders in a Tertiary conglomerate from the Guajira Peninsula, Colombia suggests that these rocks are mainly metamorphosed basaltic andesites. They are depleted in LILE elements compared to MORB, have a negative Nb-anomaly and flat to enriched REE patterns, suggesting that their protoliths evolved in a subduction related tectonic setting. They show island-arc affinities and are similar to primitive island-arc rocks described in the Caribbean. The geochemical characteristics are comparable to low-grade greenschists from the nearby Etpana Terrane, which are interpreted as part of a Cretaceous intra-oceanic arc. These data support evidence that the eclogites and the Etpana terrane rocks formed from the same volcano-sedimentary sequence. Part of this sequence was accreted onto the margin and another was incorporated into the subduction channel and metamorphosed at eclogite facies conditions. Ar-40-Ar-39 ages of 79.2 +/- 1.1Ma and 82.2 +/- 2.5Ma determined on white micas, separated from two eclogite samples, are interpreted to be related to the cooling of the main metamorphic event. The formation of a common volcano-sedimentary protolith and subsequent metamorphism of these units record the ongoing Late Cretaceous continental subduction of the South American margin within the Caribbean intra-oceanic arc subduction zone. This gave way to an arc-continent collision between the Caribbean and the South American plates, where this sequence was exhumed after the Campanian.}, language = {en} } @article{WolffHaugTimmermannetal.2011, author = {Wolff, Christian Michael and Haug, Gerald H. and Timmermann, Axel and Damste, Jaap S. Sinninghe and Brauer, Achim and Sigman, Daniel M. and Cane, Mark A. and Verschuren, Dirk}, title = {Reduced interannual rainfall variability in East Africa during the last Ice Age}, series = {Science}, volume = {333}, journal = {Science}, number = {6043}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.1203724}, pages = {743 -- 747}, year = {2011}, abstract = {Interannual rainfall variations in equatorial East Africa are tightly linked to the El Nino Southern Oscillation (ENSO), with more rain and flooding during El Nino and droughts in La Nina years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall.}, language = {en} } @article{StreichBecken2011, author = {Streich, Rita and Becken, Michael}, title = {Electromagnetic fields generated by finite-length wire sources: comparison with point dipole solutions}, series = {Geophysical prospecting}, volume = {59}, journal = {Geophysical prospecting}, number = {2}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0016-8025}, doi = {10.1111/j.1365-2478.2010.00926.x}, pages = {361 -- 374}, year = {2011}, abstract = {In present-day land and marine controlled-source electromagnetic (CSEM) surveys, electromagnetic fields are commonly generated using wires that are hundreds of metres long. Nevertheless, simulations of CSEM data often approximate these sources as point dipoles. Although this is justified for sufficiently large source-receiver distances, many real surveys include frequencies and distances at which the dipole approximation is inaccurate. For 1D layered media, electromagnetic (EM) fields for point dipole sources can be computed using well-known quasi-analytical solutions and fields for sources of finite length can be synthesized by superposing point dipole fields. However, the calculation of numerous point dipole fields is computationally expensive, requiring a large number of numerical integral evaluations. We combine a more efficient representation of finite-length sources in terms of components related to the wire and its end points with very general expressions for EM fields in 1D layered media. We thus obtain a formulation that requires fewer numerical integrations than the superposition of dipole fields, permits source and receiver placement at any depth within the layer stack and can also easily be integrated into 3D modelling algorithms. Complex source geometries, such as wires bent due to surface obstructions, can be simulated by segmenting the wire and computing the responses for each segment separately. We first describe our finite-length wire expressions and then present 1D and 3D examples of EM fields due to finite-length sources for typical land and marine survey geometries and discuss differences to point dipole fields.}, language = {en} } @article{SchmelzbachTronickeDietrich2011, author = {Schmelzbach, C. and Tronicke, Jens and Dietrich, P.}, title = {Three-dimensional hydrostratigraphic models from ground-penetrating radar and direct-push data}, series = {Journal of hydrology}, volume = {398}, journal = {Journal of hydrology}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2010.12.023}, pages = {235 -- 245}, year = {2011}, abstract = {Three-dimensional models of hydraulic conductivity and porosity are essential to understand and simulate groundwater flow in heterogeneous geological environments. However, considering the inherent limitations of traditional hydrogeological field methods in terms of resolution, alternative field approaches are needed to establish such 3-D models with sufficient accuracy. In this study, we developed a workflow combining 3-D structural information extracted from ground penetrating radar (GPR) images with 1-D in situ physical-property estimates from direct-push (DP) logging to construct a 3-D hydrostratigraphic model. To illustrate this workflow, we collected an similar to 70 m x 90 m 100 MHz 3-D GPR data set over a shallow sedimentary aquifer system resolving six different GPR facies down to similar to 15 m depth. DP logs of the relative dielectric permittivity, the relative hydraulic conductivity, the cone resistance, the sleeve friction and the pore pressure provided crucial data (1) to establish a GPR velocity model for 3-D depth migration and to check the time-to-depth conversion of the GPR data, and (2) to construct a 3-D hydrostratigraphic model. This model was built by assigning porosity values, which were computed from the DP relative dielectric permittivity logs, and DP relative hydraulic conductivity estimates to the identified GPR facies. We conclude that the integration of 3-D GPR structural images and 1-D DP logs of target physical parameters provides an efficient way for detailed 3-D subsurface characterization as needed, for example, for groundwater flow simulations.}, language = {en} } @article{KuehnRiggelsenScherbaum2011, author = {K{\"u}hn, Nicolas M. and Riggelsen, Carsten and Scherbaum, Frank}, title = {Modeling the joint probability of earthquake, site, and ground-motion parameters using bayesian networks}, series = {Bulletin of the Seismological Society of America}, volume = {101}, journal = {Bulletin of the Seismological Society of America}, number = {1}, publisher = {Seismological Society of America}, address = {El Cerrito}, issn = {0037-1106}, doi = {10.1785/0120100080}, pages = {235 -- 249}, year = {2011}, abstract = {Bayesian networks are a powerful and increasingly popular tool for reasoning under uncertainty, offering intuitive insight into (probabilistic) data-generating processes. They have been successfully applied to many different fields, including bioinformatics. In this paper, Bayesian networks are used to model the joint-probability distribution of selected earthquake, site, and ground-motion parameters. This provides a probabilistic representation of the independencies and dependencies between these variables. In particular, contrary to classical regression, Bayesian networks do not distinguish between target and predictors, treating each variable as random variable. The capability of Bayesian networks to model the ground-motion domain in probabilistic seismic hazard analysis is shown for a generic situation. A Bayesian network is learned based on a subset of the Next Generation Attenuation (NGA) dataset, using 3342 records from 154 earthquakes. Because no prior assumptions about dependencies between particular parameters are made, the learned network displays the most probable model given the data. The learned network shows that the ground-motion parameter (horizontal peak ground acceleration, PGA) is directly connected only to the moment magnitude, Joyner-Boore distance, fault mechanism, source-to-site azimuth, and depth to a shear-wave horizon of 2: 5 km/s (Z2.5). In particular, the effect of V-S30 is mediated by Z2.5. Comparisons of the PGA distributions based on the Bayesian networks with the NGA model of Boore and Atkinson (2008) show a reasonable agreement in ranges of good data coverage.}, language = {en} } @article{EndrunLebedevMeieretal.2011, author = {Endrun, Brigitte and Lebedev, Sergei and Meier, Thomas and Tirel, Celine and Friederich, Wolfgang}, title = {Complex layered deformation within the Aegean crust and mantle revealed by seismic anisotropy}, series = {Nature geoscience}, volume = {4}, journal = {Nature geoscience}, number = {3}, publisher = {Nature Publ. Group}, address = {New York}, issn = {1752-0894}, doi = {10.1038/NGEO1065}, pages = {203 -- 207}, year = {2011}, abstract = {Continental lithosphere can undergo pervasive internal deformation, often distributed over broad zones near plate boundaries. However, because of the paucity of observational constraints on three-dimensional movement at depth, patterns of flow within the lithosphere remain uncertain. Endmember models for lithospheric flow invoke deformation localized on faults or deep shear zones or, alternatively, diffuse, viscous-fluid-like flow. Here we determine seismic Rayleigh-wave anisotropy in the crust and mantle of the Aegean region, an archetypal example of continental deformation. Our data reveal a complex, depth-dependent flow pattern within the extending lithosphere. Beneath the northern Aegean Sea, fast shear wave propagation is in a North-South direction within the mantle lithosphere, parallel to the extensional component of the current strain rate field. In the south-central Aegean, where deformation is weak at present, anisotropic fabric in the lower crust runs parallel to the direction of palaeo-extension in the Miocene. The close match of orientations of regional-scale anisotropic fabric and the directions of extension during the last significant episodes of deformation implies that at least a large part of the extension in the Aegean has been taken up by distributed viscous flow in the lower crust and lithospheric mantle.}, language = {en} } @article{HajialioghliMoazzenJahangirietal.2011, author = {Hajialioghli, Robab and Moazzen, Mohssen and Jahangiri, Ahmad and Oberh{\"a}nsli, Roland and Mocek, Beate and Altenberger, Uwe}, title = {Petrogenesis and tectonic evolution of metaluminous sub-alkaline granitoids from the Takab Complex, NW Iran}, series = {Geological magazine}, volume = {148}, journal = {Geological magazine}, number = {2}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0016-7568}, doi = {10.1017/S0016756810000683}, pages = {250 -- 268}, year = {2011}, abstract = {The Takab complex is composed of a variety of metamorphic rocks including amphibolites, metapelites, mafic granulites, migmatites and meta-ultramafics, which are intruded by the granitoid. The granitoid magmatic activity occurred in relation to the subduction of the Neo-Tethys oceanic crust beneath the Iranian crust during Tertiary times. The granitoids are mainly granodiorite, quartz monzodiorite, monzonite and quartz diorite. Chemically, the magmatic rocks are characterized by ASI < 1.04, AI < 0.87 and high contents of CaO (up to similar to 14.5 wt \%), which are consistent with the I-type magmatic series. Low FeO(t)/(FeO(t)+MgO) values (< 0.75) as well as low Nb, Y and K(2)O contents of the investigated rocks resemble the calc-alkaline series. Low SiO(2), K(2)O/Na(2)O and Al(2)O(3) accompanied by high CaO and FeO contents indicate melting of metabasites as an appropriate source for the intrusions. Negative Ti and Nb anomalies verify a metaluminous crustal origin for the protoliths of the investigated igneous rocks. These are comparable with compositions of the associated mafic migmatites, in the Takab metamorphic complex, which originated from the partial melting of amphibolites. Therefore, crustal melting and a collision-related origin for the Takab calc-alkaline intrusions are proposed here on the basis of mineralogy and geochemical characteristics. The P-T evolution during magmatic crystallization and subsolidus cooling stages is determined by the study of mineral chemistry of the granodiorite and the quartz diorite. Magmatic crystallization pressure and temperature for the quartz-diorite and the granodiorite are estimated to be P similar to 7.8 +/- 2.5 kbar, T similar to 760 +/- 75 degrees C and P similar to 5 +/- 1 kbar, T similar to 700 degrees C, respectively. Subsolidus conditions are consistent with temperatures of similar to 620 degrees C and similar to 600 degrees C, and pressures of similar to 5 kbar and similar to 3.5 kbar for the quartz-diorite and the granodiorite, respectively.}, language = {en} } @article{TokeArrowsmithRymeretal.2011, author = {Toke, Nathan A. and Arrowsmith, J. Ramon and Rymer, Michael J. and Landgraf, Angela and Haddad, David E. and Busch, Melanie and Coyan, Joshua and Hannah, Alexander}, title = {Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California}, series = {Geology}, volume = {39}, journal = {Geology}, number = {3}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G31498.1}, pages = {243 -- 246}, year = {2011}, abstract = {Investigation of a right-laterally offset channel at the Miller's Field paleoseismic site yields a late Holocene slip rate of 26.2 +6.4/-4.3 mm/yr (1 sigma) for the main trace of the San Andreas fault at Parkfield, California. This is the first well-documented geologic slip rate between the Carrizo and creeping sections of the San Andreas fault. This rate is lower than Holocene measurements along the Carrizo Plain and rates implied by far-field geodetic measurements (similar to 35 mm/yr). However, the rate is consistent with historical slip rates, measured to the northwest, along the creeping section of the San Andreas fault (<30 mm/yr). The paleoseismic exposures at the Miller's Field site reveal a pervasive fabric of clay shear bands, oriented clockwise oblique to the San Andreas fault strike and extending into the uppermost stratigraphy. This fabric is consistent with dextral aseismic creep and observations of surface slip from the 28 September 2004 M6 Parkfield earthquake. Together, this slip rate and deformation fabric suggest that the historically observed San Andreas fault slip behavior along the Parkfield section has persisted for at least a millennium, and that significant slip is accommodated by structures in a zone beyond the main San Andreas fault trace.}, language = {en} } @article{TranThanhTuanScherbaumMalischewsky2011, author = {Tran Thanh Tuan, and Scherbaum, Frank and Malischewsky, Peter G.}, title = {On the relationship of peaks and troughs of the ellipticity (H/V) of Rayleigh waves and the transmission response of single layer over half-space models}, series = {Geophysical journal international}, volume = {184}, journal = {Geophysical journal international}, number = {2}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2010.04863.x}, pages = {793 -- 800}, year = {2011}, abstract = {One of the key challenges in the context of local site effect studies is the determination of frequencies where the shakeability of the ground is enhanced. In this context, the H/V technique has become increasingly popular and peak frequencies of H/V spectral ratio are sometimes interpreted as resonance frequencies of the transmission response. In the present study, assuming that Rayleigh surface wave is dominant in H/V spectral ratio, we analyse theoretically under which conditions this may be justified and when not. We focus on 'layer over half-space' models which, although seemingly simple, capture many aspects of local site effects in real sedimentary structures. Our starting point is the ellipticity of Rayleigh waves. We use the exact formula of the H/V-ratio presented by Malischewsky \& Scherbaum (2004) to investigate the main characteristics of peak and trough frequencies. We present a simple formula illustrating if and where H/V-ratio curves have sharp peaks in dependence of model parameters. In addition, we have constructed a map, which demonstrates the relation between the H/V-peak frequency and the peak frequency of the transmission response in the domain of the layer's Poisson ratio and the impedance contrast. Finally, we have derived maps showing the relationship between the H/V-peak and trough frequency and key parameters of the model such as impedance contrast. These maps are seen as diagnostic tools, which can help to guide the interpretation of H/V spectral ratio diagrams in the context of site effect studies.}, language = {en} } @article{HainSigmanHaug2011, author = {Hain, Mathis P. and Sigman, Daniel M. and Haug, Gerald H.}, title = {Shortcomings of the isolated abyssal reservoir model for deglacial radiocarbon changes in the mid-depth Indo-Pacific Ocean}, series = {Geophysical research letters}, volume = {38}, journal = {Geophysical research letters}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2010GL046158}, pages = {6}, year = {2011}, abstract = {Severely negative Delta(14)C anomalies from the mid-depth Pacific and the Arabian Sea have been taken as support for the hypothesized deglacial release of a previously isolated, extremely (14)C-deplete deep ocean carbon reservoir. We report box model simulations that cast doubt on both the existence of the hypothesized deep reservoir and its ability to explain the mid-depth Delta(14)C anomalies. First, the degree of ice age isolation needed to substantially reduce the deep Delta(14)C of the deep reservoir causes anoxia and the trapping of alkalinity from CaCO(3) dissolution, the latter increasing atmospheric CO(2). Second, even with a completely (14)C-free deep reservoir, achieving the mid-depth Delta(14)C anomalies of observed duration requires ad hoc stifling of aspects of deep circulation to prevent rapid dissipation of the anomalous (14)C-free carbon to the rest of the ocean and the atmosphere. We suggest that the mid-depth anomalies do not record basin-scale Delta(14)C changes but are instead local phenomena.}, language = {en} } @article{MaerkerPelacaniSchroeder2011, author = {Maerker, Michael and Pelacani, Samanta and Schroeder, Boris}, title = {A functional entity approach to predict soil erosion processes in a small Plio-Pleistocene Mediterranean catchment in Northern Chianti, Italy}, series = {Geomorphology : an international journal on pure and applied geomorphology}, volume = {125}, journal = {Geomorphology : an international journal on pure and applied geomorphology}, number = {4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2010.10.022}, pages = {530 -- 540}, year = {2011}, abstract = {In this paper we evaluate different methods to predict soil erosion processes. We derived different layers of predictor variables for the study area in the Northern Chianti, Italy, describing the soil-lithologic complex, land use, and topographic characteristics. For a subcatchment of the Orme River, we mapped erosion processes by interpreting aerial photographs and field observations. These were classified as erosional response units (ERU), i.e. spatial areas of homogeneous erosion processes. The ERU were used as the response variable in the soil erosion modelling process. We applied two models i) bootstrap aggregation (Random Forest: RF), and ii) stochastic gradient boosting (TreeNet: TN) to predict the potential spatial distribution of erosion processes for the entire Orme River catchment. The models are statistically evaluated using training data and a set of performance parameters such as the area under the receiver operating characteristic curve (AUC), Cohen's Kappa, and pseudo R2. Variable importance and response curves provide further insight into controlling factors of erosion. Both models provided good performance in terms of classification and calibration; however, TN outperformed RF. Similar classes such as active and inactive landslides can be discriminated and well interpreted by considering response curves and relative variable importance. The spatial distribution of the predicted erosion susceptibilities generally follows topographic constraints and is similar for both models. Hence, the model-based delineation of ERU on the basis of soil and terrain information is a valuable tool in geomorphology; it provides insights into factors controlling erosion processes and may allow the extrapolation and prediction of erosion processes in unsurveyed areas.}, language = {en} } @article{BergerSchmidEngietal.2011, author = {Berger, Alfons and Schmid, Stefan M. and Engi, Martin and Bousquet, Romain and Wiederkehr, Michael}, title = {Mechanisms of mass and heat transport during Barrovian metamorphism: A discussion based on field evidence from the Central Alps (Switzerland/northern Italy)}, series = {Tectonics}, volume = {30}, journal = {Tectonics}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1029/2009TC002622}, pages = {17}, year = {2011}, abstract = {Tectonic and metamorphic data for the Central Alps (Switzerland/Italy) are used to discuss this classic example of a Barrovian metamorphic terrain, notably the evolution of its thermal structure in space and time. Available P-T-t data indicate variable contributions of advective and conductive heat transport during collision and subsequent cooling and exhumation. Some areas experienced a prolonged period of partial melting while other areas, at the same time, show but moderate heating. The Barrow-type metamorphic field gradient observed in the final orogen is the result of two distinct tectonic processes, with their related advective and conductive heat transport processes. The two tectonic processes are (1) accretion of material within a subduction channel related to decompression and emplacement of high-pressure units in the middle crust and (2) wedging and related nappe formation in the continental lower plate. The second process postdates the first one. Wedging and underthrusting of continental lower plate material produces heat input into lower crustal levels, and this process is responsible for predominantly conductive heat transport in the overlying units. The interacting processes lead to different maximum temperatures at different times, producing the final Barrovian metamorphic field gradient. The south experienced rapid cooling, whereas the north shows moderate cooling rates. This discrepancy principally reflects differences in the temperature distribution in the deeper crust prior to cooling. Differences in the local thermal gradient that prevailed before the cooling also determined the relationships between cooling rate and exhumation rate in the different areas. Citation: Berger, A., S. M. Schmid, M. Engi, R. Bousquet, and M. Wiederkehr (2011), Mechanisms of mass and heat transport during Barrovian metamorphism: A discussion based on field evidence from the Central Alps (Switzerland/northern Italy), Tectonics, 30, TC1007, doi:10.1029/2009TC002622.}, language = {en} } @article{WielandDalchowSommeretal.2011, author = {Wieland, Ralf and Dalchow, Claus and Sommer, Michael and Fukuda, Kyoko}, title = {Multi-Scale Landscape Analysis (MSLA) a method to identify correlation of relief with ecological point data}, series = {Ecological informatics : an international journal on ecoinformatics and computational ecolog}, volume = {6}, journal = {Ecological informatics : an international journal on ecoinformatics and computational ecolog}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1574-9541}, doi = {10.1016/j.ecoinf.2010.09.002}, pages = {164 -- 169}, year = {2011}, abstract = {A common problem in ecology is identifying the relationship between relief and site properties obtainable only by point measurements. The method of Multi-Scale Landscape Analysis (MSLA) identifies such correlations. MSLA combines frequency filtering of the digital elevation model (DEM) with an estimation of the optimum filter coefficients using an optimization procedure. Tested using point data of soil decarbonation from a German young moraine landscape, MSLA provided significant results. Implemented within open source software SAMT. MSLA is comfortable and flexible to use, offering applications for numerous other spatial analysis problems.}, language = {en} } @article{MischkeZhang2011, author = {Mischke, Steffen and Zhang, Chengjun}, title = {Ostracod distribution in Ulungur Lake (Xinjiang, China) and a reassessed Holocene record}, series = {Ecological research}, volume = {26}, journal = {Ecological research}, number = {1}, publisher = {Springer}, address = {Tokyo}, issn = {0912-3814}, doi = {10.1007/s11284-010-0768-1}, pages = {133 -- 145}, year = {2011}, abstract = {Ostracod shells in surface sediments from Ulungur Lake (Xinjiang, China) belong mainly to Limnocythere inopinata as the dominant species, and Candona neglecta and Darwinula stevensoni as accompanying, less abundant taxa. Shells of an additional nine species were recorded only sporadically. The three most abundant ostracods have wide tolerance ranges in terms of salinity, substrate and water depth. The similarly recorded bivalve Pisidium subtruncatum, and the gastropods Gyraulus chinensis and Radix auricularia belong to the most tolerant representatives of the genera. The bivalve and gastropods, in addition to the ostracod assemblage, reflect the fact that Ulungur Lake has experienced strong lake level and salinity variations due to water withdrawal in the catchment and the counteracting diversion of river waters to the lake in recent decades. The substrate in Ulungur Lake is typically fine-grained, apart from the delta region of the Ulungur River channel, which is marked by relatively coarse-grained detrital sediments barren of ostracod shells. This channel was created 40 years ago to divert water to Ulungur Lake and support its local fisheries and recreational facilities. A reassessed Holocene ostracod record from the lake shows that a significantly higher salinity and lower lake level existed in the early Holocene before 6.0 ka in response to the regional climate. In contrast, a higher lake level and lowest salinity is inferred for the late Holocene period between ca. 3.6 and 1.3 ka before present. Afterwards, the lake level declined and salinity increased in response to regional moisture reduction, although conditions similar to the early Holocene lake status were not re-established. Our surface-sediment-derived data provide a baseline for analysis of future environmental variations due to global climate change and regional water management.}, language = {en} } @article{LappeKallmeyer2011, author = {Lappe, Michael and Kallmeyer, Jens}, title = {A cell extraction method for oily sediments}, series = {Frontiers in microbiology}, volume = {2}, journal = {Frontiers in microbiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-302X}, doi = {10.3389/fmicb.2011.00233}, pages = {11}, year = {2011}, abstract = {Hydrocarbons can be found in many different habitats and represent an important carbon source for microbes. As fossil fuels, they are also an important economical resource and through natural seepage or accidental release they can be major pollutants. DNA-specific stains and molecular probes bind to hydrocarbons, causing massive background fluorescence, thereby hampering cell enumeration. The cell extraction procedure of Kallmeyer et al. (2008) separates the cells from the sediment matrix. In principle, this technique can also be used to separate cells from oily sediments, but it was not originally optimized for this application. Here we present a modified extraction method in which the hydrocarbons are removed prior to cell extraction. Due to the reduced background fluorescence the microscopic image becomes clearer, making cell identification, and enumeration much easier. Consequently, the resulting cell counts from oily samples treated according to our new protocol are significantly higher than those treated according to Kallmeyer et al. (2008). We tested different amounts of a variety of solvents for their ability to remove hydrocarbons and found that n-hexane and in samples containing more mature oils methanol, delivered the best results. However, as solvents also tend to lyse cells, it was important to find the optimum solvent to sample ratio, at which hydrocarbon extraction is maximized and cell lysis minimized. A volumetric ratio of 1:2-1:5 between a formalin-fixed sediment slurry and solvent delivered highest cell counts. Extraction efficiency was around 30-50\% and was checked on both oily samples spiked with known amounts of E. coli cells and oil-free samples amended with fresh and biodegraded oil. The method provided reproducible results on samples containing very different kinds of oils with regard to their degree of biodegradation. For strongly biodegraded oil MeOH turned out to be the most appropriate solvent, whereas for less biodegraded samples n-hexane delivered best results.}, language = {en} } @article{KrauseBuseMaternetal.2011, author = {Krause, Rolf Harald and Buse, Joern and Matern, Andrea and Schroeder, Boris and Haerdtle, Werner and Assmann, Thorsten}, title = {Eresus kollari (Araneae: Eresidae) calls for heathland management}, series = {The Journal of arachnology}, volume = {39}, journal = {The Journal of arachnology}, number = {3}, publisher = {American Arachnological Society}, address = {College Park}, issn = {0161-8202}, pages = {384 -- 392}, year = {2011}, abstract = {Northwest Europe's largest heather-dominated sandy habitats are located in the nature reserve Luneburger Heide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as the ladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of these species. The habitat requirements of this endangered spider species were investigated in order to obtain data that will help stabilize the last remnants of the species' population in northwest Germany. Several heathland habitats were surveyed by pitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic regression and boosted regression trees (BRT). Both methods showed that three habitat variables are of prime relevance in predicting the occurrence of E. kollari: a) thickness of the organic layer (a negative effect), b) soil temperature at a depth of 10 cm, and c) Calluna cover in the herb layer (both have positive effect). Our results show that choppering (removing above-ground biomass and most of O-layer) and burning are likely appropriate heathland management measures for the conservation of E. kollari. Such measures improve the species' habitat quality by creating a heterogenic (small-scaled) heathland structure with suitable microhabitats. As Calluna heathlands show a clear senescence of the dominant heather, it is essential that those habitat patches be conserved. Further measures, such as transfer experiments, are recommended.}, language = {en} } @article{SchluneggerNortonZeilinger2011, author = {Schlunegger, Fritz and Norton, Kevin P. and Zeilinger, Gerold}, title = {Climatic forcing on channel profiles in the eastern cordillera of the Coroico Region, Bolivia}, series = {The journal of geology}, volume = {119}, journal = {The journal of geology}, number = {1}, publisher = {Univ. of Chicago Press}, address = {Chicago}, issn = {0022-1376}, doi = {10.1086/657407}, pages = {97 -- 107}, year = {2011}, abstract = {Orographic precipitation has a large impact on channel morphology and rock uplift via a positive feedback to erosion. We show that in the Eastern Cordillera of Bolivia, channel concavities reach their highest values where annual precipitation increases in the downstream direction, exceeding 3000 mm. The steepest channels are upstream of this zone of high concavity, where precipitation rates are <1000 mm yr(-1). Channels exhibit graded forms both upstream and downstream of this transient reach. We conclude that the prolonged effect of orographic erosion and related tectonic uplift is the preservation of channels with extreme concavities in the Eastern Cordillera.}, language = {en} } @article{BenmehdiMakaravaBenhamidoucheetal.2011, author = {Benmehdi, Sabah and Makarava, Natallia and Benhamidouche, N. and Holschneider, Matthias}, title = {Bayesian estimation of the self-similarity exponent of the Nile River fluctuation}, series = {Nonlinear processes in geophysics}, volume = {18}, journal = {Nonlinear processes in geophysics}, number = {3}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1023-5809}, doi = {10.5194/npg-18-441-2011}, pages = {441 -- 446}, year = {2011}, abstract = {The aim of this paper is to estimate the Hurst parameter of Fractional Gaussian Noise (FGN) using Bayesian inference. We propose an estimation technique that takes into account the full correlation structure of this process. Instead of using the integrated time series and then applying an estimator for its Hurst exponent, we propose to use the noise signal directly. As an application we analyze the time series of the Nile River, where we find a posterior distribution which is compatible with previous findings. In addition, our technique provides natural error bars for the Hurst exponent.}, language = {en} } @article{WintleBekessyKeithetal.2011, author = {Wintle, Brendan A. and Bekessy, Sarah A. and Keith, David A. and van Wilgen, Brian W. and Cabeza, Mar and Schr{\"o}der-Esselbach, Boris and Carvalho, Silvia B. and Falcucci, Alessandra and Maiorano, Luigi and Regan, Tracey J. and Rondinini, Carlo and Boitani, Luigi and Possingham, Hugh P.}, title = {Ecological-economic optimization of biodiversity conservation under climate change}, series = {Nature climate change}, volume = {1}, journal = {Nature climate change}, number = {7}, publisher = {Nature Publ. Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/NCLIMATE1227}, pages = {355 -- 359}, year = {2011}, abstract = {Substantial investment in climate change research has led to dire predictions of the impacts and risks to biodiversity. The Intergovernmental Panel on Climate Change fourth assessment report(1) cites 28,586 studies demonstrating significant biological changes in terrestrial systems(2). Already high extinction rates, driven primarily by habitat loss, are predicted to increase under climate change(3-6). Yet there is little specific advice or precedent in the literature to guide climate adaptation investment for conserving biodiversity within realistic economic constraints(7). Here we present a systematic ecological and economic analysis of a climate adaptation problem in one of the world's most species-rich and threatened ecosystems: the South African fynbos. We discover a counterintuitive optimal investment strategy that switches twice between options as the available adaptation budget increases. We demonstrate that optimal investment is nonlinearly dependent on available resources, making the choice of how much to invest as important as determining where to invest and what actions to take. Our study emphasizes the importance of a sound analytical framework for prioritizing adaptation investments(4). Integrating ecological predictions in an economic decision framework will help support complex choices between adaptation options under severe uncertainty. Our prioritization method can be applied at any scale to minimize species loss and to evaluate the robustness of decisions to uncertainty about key assumptions.}, language = {en} } @article{LoosElsenbeer2011, author = {Loos, Martin and Elsenbeer, Helmut}, title = {Topographic controls on overland flow generation in a forest - An ensemble tree approach}, series = {Journal of hydrology}, volume = {409}, journal = {Journal of hydrology}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2011.08.002}, pages = {94 -- 103}, year = {2011}, abstract = {Overland flow is an important hydrological pathway in many forests of the humid tropics. Its generation is subject to topographic controls at differing spatial scales. Our objective was to identify such controls on the occurrence of overland flow in a lowland tropical rainforest. To this end, we installed 95 overland flow detectors (OFDs) in four nested subcatchments of the Lutzito catchment on Barro Colorado Island, Panama, and monitored the frequency of overland flow occurrence during 18 rainfall events at each OFD location temporal frequency. For each such location, we derived three non-digital terrain attributes and 17 digital ones, of which 15 were based on Digital Elevation Models (DEMs) of three different resolutions. These attributes then served as input into a Random Forest ensemble tree model to elucidate the importance and partial and joint dependencies of topographic controls for overland flow occurrence. Lutzito features a high median temporal frequency in overland flow occurrence of 0.421 among OFD locations. However, spatial temporal frequencies of overland flow occurrence vary strongly among these locations and the subcatchments of Lutzito catchment. This variability is best explained by (1) microtopography, (2) coarse terrain sloping and (3) various measures of distance-to-channel, with the contribution of all other terrain attributes being small. Microtopographic features such as concentrated flowlines and wash areas produce highest temporal frequencies, whereas the occurrence of overland flow drops sharply for flow distances and terrain sloping beyond certain threshold values. Our study contributes to understanding both the spatial controls on overland flow generation and the limitations of terrain attributes for the spatially explicit prediction of overland flow frequencies.}, language = {en} } @article{ClarkeBurbank2011, author = {Clarke, Brian A. and Burbank, Douglas W.}, title = {Quantifying bedrock-fracture patterns within the shallow subsurface Implications for rock mass strength, bedrock landslides, and erodibility}, series = {Journal of geophysical research : Earth surface}, volume = {116}, journal = {Journal of geophysical research : Earth surface}, number = {20}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9003}, doi = {10.1029/2011JF001987}, pages = {22}, year = {2011}, abstract = {The role of bedrock fractures and rock mass strength is often considered a primary influence on the efficiency of surface processes and the morphology of landscapes. Quantifying bedrock characteristics at hillslope scales, however, has proven difficult. Here, we present a new field-based method for quantifying the depth and apparent density of bedrock fractures within the shallow subsurface based on seismic refraction surveys. We examine variations in subsurface fracture patterns in both Fiordland and the Southern Alps of New Zealand to better constrain the influence of bedrock properties in governing rates and patterns of landslides, as well as the morphology of threshold landscapes. We argue that intense tectonic deformation produces uniform bedrock fracturing with depth, whereas geomorphic processes produce strong fracture gradients focused within the shallow subsurface. Additionally, we argue that hillslope strength and stability are functions of both the intact rock strength and the density of bedrock fractures, such that for a given intact rock strength, a threshold fracture-density exists that delineates between stable and unstable rock masses. In the Southern Alps, tectonic forces have pervasively fractured intrinsically weak rock to the verge of instability, such that the entire rock mass is susceptible to failure and landslides can potentially extend to great depths. Conversely, in Fiordland, tectonic fracturing of the strong intact rock has produced fracture densities less than the regional stability threshold. Therefore, bedrock failure in Fiordland generally occurs only after geomorphic fracturing has further reduced the rock mass strength. This dependence on geomorphic fracturing limits the depths of bedrock landslides to within this geomorphically weakened zone.}, language = {en} } @article{PostbergGruenHoranyietal.2011, author = {Postberg, Frank and Gr{\"u}n, Eberhard and Horanyi, Mihaly and Kempf, Sascha and Krueger, Harald and Schmidt, J{\"u}rgen and Spahn, Frank and Srama, Ralf and Sternovsky, Zoltan and Trieloff, Mario}, title = {Compositional mapping of planetary moons by mass spectrometry of dust ejecta}, series = {Planetary and space science}, volume = {59}, journal = {Planetary and space science}, number = {14}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2011.05.001}, pages = {1815 -- 1825}, year = {2011}, abstract = {Classical methods to analyze the surface composition of atmosphereless planetary objects from an orbiter are IR and gamma ray spectroscopy and neutron backscatter measurements. The idea to analyze surface properties with an in-situ instrument has been proposed by Johnson et al. (1998). There, it was suggested to analyze Europa's thin atmosphere with an ion and neutral gas spectrometer. Since the atmospheric components are released by sputtering of the moon's surface, they provide a link to surface composition. Here we present an improved, complementary method to analyze rocky or icy dust particles as samples of planetary objects from which they were ejected. Such particles, generated by the ambient meteoroid bombardment that erodes the surface, are naturally present on all atmosphereless moons and planets. The planetary bodies are enshrouded in clouds of ballistic dust particles, which are characteristic samples of their surfaces. In situ mass spectroscopic analysis of these dust particles impacting onto a detector of an orbiting spacecraft reveals their composition. Recent instrumental developments and tests allow the chemical characterization of ice and dust particles encountered at speeds as low as 1 km/s and an accurate reconstruction of their trajectories. Depending on the sampling altitude, a dust trajectory sensor can trace back the origin of each analyzed grain with about 10 km accuracy at the surface. Since the detection rates are of the order of thousand per orbit, a spatially resolved mapping of the surface composition can be achieved. Certain bodies (e.g., Europa) with particularly dense dust clouds, could provide impact statistics that allow for compositional mapping even on single flybys. Dust impact velocities are in general sufficiently high at orbiters about planetary objects with a radius > 1000 km and with only a thin or no atmosphere. In this work we focus on the scientific benefit of a dust spectrometer on a spacecraft orbiting Earth's Moon as well as Jupiter's Galilean satellites. This 'dust spectrometer' approach provides key chemical and isotopic constraints for varying provinces or geological formations on the surfaces, leading to better understanding of the body's geological evolution.}, language = {en} } @article{MoenickesSchneiderMuehleetal.2011, author = {Moenickes, Sylvia and Schneider, Anne-Kathrin and Muehle, Lesley and Rohe, Lena and Richter, Otto and Suhling, Frank}, title = {From population-level effects to individual response: modelling temperature dependence in Gammarus pulex}, series = {The journal of experimental biology}, volume = {214}, journal = {The journal of experimental biology}, number = {21}, publisher = {Company of Biologists Limited}, address = {Cambridge}, issn = {0022-0949}, doi = {10.1242/jeb.061945}, pages = {3678 -- 3687}, year = {2011}, abstract = {Population-level effects of global warming result from concurrent direct and indirect processes. They are typically described by physiologically structured population models (PSPMs). Therefore, inverse modelling offers a tool to identify parameters of individual physiological processes through population-level data analysis, e. g. the temperature dependence of growth from size-frequency data of a field population. Here, we make use of experiments under laboratory conditions, in mesocosms and field monitoring to determine the temperature dependence of growth and mortality of Gammarus pulex. We found an optimum temperature for growth of approximately 17 degrees C and a related temperature coefficient, Q(10), of 1.5 degrees C(-1), irrespective of whether we classically fitted individual growth curves or applied inverse modelling based on PSPMs to laboratory data. From a comparison of underlying data sets we conclude that applying inverse modelling techniques to population-level data results in meaningful response parameters for physiological processes if additional temperature-driven effects, including within-population interaction, can be excluded or determined independently. If this is not the case, parameter estimates describe a cumulative response, e. g. comprising temperature-dependent resource dynamics. Finally, fluctuating temperatures in natural habitats increased the uncertainty in parameter values. Here, PSPM should be applied for virtual monitoring in order to determine a sampling scheme that comprises important dates to reduce parameter uncertainty.}, language = {en} } @article{KahmenDawsonViethetal.2011, author = {Kahmen, Ansgar and Dawson, Todd E. and Vieth, Andrea and Sachse, Dirk}, title = {Leaf wax n-alkane delta D values are determined early in the ontogeny of Populus trichocarpa leaves when grown under controlled environmental conditions}, series = {Plant, cell \& environment : cell physiology, whole-plant physiology, community physiology}, volume = {34}, journal = {Plant, cell \& environment : cell physiology, whole-plant physiology, community physiology}, number = {10}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0140-7791}, doi = {10.1111/j.1365-3040.2011.02360.x}, pages = {1639 -- 1651}, year = {2011}, abstract = {The stable hydrogen isotope ratios (delta D) of leaf wax n-alkanes record valuable information on plant and ecosystem water relations. It remains, however, unknown if leaf wax n-alkane delta D values record only environmental variation during the brief period of time of leaf growth or if leaf wax n-alkane delta D values are affected by environmental variability throughout the entire lifespan of a leaf. To resolve these uncertainties, we irrigated Populus trichocarpa trees with a pulse of deuterium-enriched water and used compound-specific stable hydrogen isotope analyses to test if the applied tracer could be recovered from leaf wax n-alkanes of leaves that were at different stages of their development during the tracer application. Our experiment revealed that only leaf wax n-alkanes from leaves that had developed during the time of the tracer application were affected, while leaves that were already fully matured at the time of the tracer application were not. We conclude from our study that under controlled environmental conditions, leaf wax n-alkanes are synthesized only early in the ontogeny of a leaf. Our experiment has implications for the interpretation of leaf wax n-alkane delta D values in an environmental context, as it suggests that these compounds record only a brief period of the environmental variability that a leaf experiences throughout its life.}, language = {en} } @article{SchulzCayuelaReyBenayasetal.2011, author = {Schulz, Jennifer J. and Cayuela, Luis and Rey-Benayas, Jose M. and Schr{\"o}der-Esselbach, Boris}, title = {Factors influencing vegetation cover change in Mediterranean Central Chile (1975-2008)}, series = {Applied vegetation science : official organ of the International Association for Vegetation Science}, volume = {14}, journal = {Applied vegetation science : official organ of the International Association for Vegetation Science}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1402-2001}, doi = {10.1111/j.1654-109X.2011.01135.x}, pages = {571 -- 582}, year = {2011}, abstract = {Questions: Which are the factors that influence forest and shrubland loss and regeneration and their underlying drivers? Location: Central Chile, a world biodiversity hotspot. Methods: Using land-cover data from the years 1975, 1985, 1999 and 2008, we fitted classification trees and multiple logistic regression models to account for the relationship between different trajectories of vegetation change and a range of biophysical and socio-economic factors. Results: The variables that most consistently showed significant effects on vegetation change across all time-intervals were slope and distance to primary roads. We found that forest and shrubland loss on one side and regeneration on the other often displayed opposite patterns in relation to the different explanatory variables. Deforestation was positively related to distance to primary roads and to distance within forest edges and was favoured by a low insolation and a low slope. In turn, forest regeneration was negatively related to the distance to primary roads and positively to the distance to the nearest forest patch, insolation and slope. Shrubland loss was positively influenced by slope and distance to cities and primary roads and negatively influenced by distance to rivers. Conversely, shrubland regeneration was negatively related to slope, distance to cities and distance to primary roads and positively related to distance from existing forest patches and distance to rivers. Conclusions: This article reveals how biophysical and socioeconomic factors influence vegetation cover change and the underlying social, political and economical drivers. This assessment provides a basis for management decisions, considering the crucial role of perennial vegetation cover for sustaining biodiversity and ecosystem services.}, language = {en} } @article{StreichBecken2011, author = {Streich, R. and Becken, Michael}, title = {Sensitivity of controlled-source electromagnetic fields in planarly layered media}, series = {Geophysical journal international}, volume = {187}, journal = {Geophysical journal international}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2011.05203.x}, pages = {705 -- 728}, year = {2011}, abstract = {The study of electromagnetic (EM) field sensitivities is useful for assessing the feasibility of controlled-source electromagnetic (CSEM) surveys. Sensitivity calculations are also a principal building block of EM inversion schemes. Sensitivities are formally given by the derivatives of the EM field components with respect to conductivity. For horizontally layered media, these derivatives can be evaluated analytically, offering advantages in computational efficiency and accuracy over numerical evaluation. We present a complete set of explicit analytic expressions for the EM field sensitivities in 1-D VTI-anisotropic media for horizontal and vertical electric and magnetic dipole sources, and also for finite horizontal electric sources. Since our derivations are based on a formulation for EM fields that is quite general in allowing for sources and receivers at any depth, our sensitivity expressions exhibit the same generality. We verify our expressions by comparison to numerical solutions, and finally present application examples that demonstrate the utility and versatility of these expressions for CSEM feasibility studies.}, language = {en} } @article{SchefflerNeillKruscheetal.2011, author = {Scheffler, Raphael and Neill, Christopher and Krusche, Alex V. and Elsenbeer, Helmut}, title = {Soil hydraulic response to land-use change associated with the recent soybean expansion at the Amazon agricultural frontier}, series = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, volume = {144}, journal = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8809}, doi = {10.1016/j.agee.2011.08.016}, pages = {281 -- 289}, year = {2011}, abstract = {Clearing for large-scale soy production and the displacement of cattle-breeding by soybeans are major features of land-use change in the lowland Amazon that can alter hydrologic properties of soils and the runoff generation over large areas. We measured infiltrability and saturated hydraulic conductivity (Ksat) under natural forest, pasture, and soybeans on Oxisols in a region of rapid soybean expansion in Mato Grosso, Brazil. The forest-pasture conversion reduced infiltrability from 1258 to 100 mm/h and Ksat at all depths. The pasture-soy conversion increased infiltrability from 100 to 469 mm/h (attributed to shallow disking), did not affect Ksat at 12.5 cm, but decreased Ksat at 30 cm from 122 to 80 mm/h, suggesting that soybean cultivation enhances subsoil compaction. Permeability decreased markedly with depth under forest, did not change under pasture, and averaged out at one fourth the forest value under soybeans with a similar pattern of anisotropy. Comparisons of permeability with rainfall intensities indicated that land-use change did not alter the predominantly vertical water movement within the soil. We conclude that this landscape is well buffered against land-use changes regarding near-surface hydrology, even though short-lived ponding and perched water tables may occur locally during high-intensity rainfall on pastures and under soybeans.}, language = {en} } @article{ScherbaumKuehn2011, author = {Scherbaum, Frank and K{\"u}hn, Nicolas M.}, title = {Logic tree branch weights and probabilities summing up to one is not enough}, series = {Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute}, volume = {27}, journal = {Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute}, number = {4}, publisher = {Earthquake Engineering Research Institute}, address = {Oakland}, issn = {8755-2930}, doi = {10.1193/1.3652744}, pages = {1237 -- 1251}, year = {2011}, abstract = {Logic trees have become the most popular tool for the quantification of epistemic uncertainties in probabilistic seismic hazard assessment (PSHA). In a logic-tree framework, epistemic uncertainty is expressed in a set of branch weights, by which an expert or an expert group assigns degree-of-belief values to the applicability of the corresponding branch models. Despite the popularity of logic-trees, however, one finds surprisingly few clear commitments to what logic-tree branch weights are assumed to be (even by hazard analysts designing logic trees). In the present paper we argue that it is important for hazard analysts to accept the probabilistic framework from the beginning for assigning logic-tree branch weights. In other words, to accept that logic-tree branch weights are probabilities in the axiomatic sense, independent of one's preference for the philosophical interpretation of probabilities. We demonstrate that interpreting logic-tree branch weights merely as a numerical measure of "model quality," which are then subsequently normalized to sum up to unity, will with increasing number of models inevitably lead to an apparent insensitivity of hazard curves on the logic-tree branch weights, which may even be mistaken for robustness of the results. Finally, we argue that assigning logic-tree branch weights in a sequential fashion may improve their logical consistency.}, language = {en} } @article{AkalKoralayCandanetal.2011, author = {Akal, Cuneyt and Koralay, O. Ersin and Candan, Osman and Oberh{\"a}nsli, Roland and Chen, Fukun}, title = {Geodynamic significance of the early triassic karaburun granitoid (Western Turkey) for the opening history of Neo-Tethys}, series = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, volume = {20}, journal = {Turkish journal of earth sciences = T{\"u}rk yerbilimleri dergisi}, number = {3}, publisher = {T{\"u}bitak}, address = {Ankara}, issn = {1300-0985}, doi = {10.3906/yer-1008-1}, pages = {255 -- 271}, year = {2011}, abstract = {The Karaburun Peninsula, which is considered part of the Anatolide-Tauride Block of Turkey, contains clastic and carbonate sequences deposited on the northern margin of Gondwana. The Palaeozoic clastic sequence, which is intruded by the Early Triassic granitoid and tectonically overlies a Mesozoic melange sequence, can be divided into three subunits: a lower clastic subunit consisting of a sandstone-shale alternation, an upper clastic subunit consisting of black chert-bearing shales, sandstone and conglomerate, and a Permo-Carboniferous carbonate subunit. The lower Triassic Karaburun I-type granitoid has a high initial Sr-87/Sr-86 ratio (0.709021-0.709168), and low Nd-143/Nd-144 ratio (0.512004-0.512023) and epsilon Nd (-5.34 to -5.70) isotopic values. Geochronological data indicate a crystallization (intrusion) age of 247.1 +/- 2.0 Ma (Scythian). Geochemically, the acidic magmatism reflects a subduction-related continental-arc basin tectonic setting, which can be linked to the opening of the northern branch of Neo-Tethys as a continental back-arc rifting basin on the northern margin of Gondwana. This can be related to the closure through southward subduction of the Palaeotethys Ocean beneath Gondwana.}, language = {en} } @article{MohsenAschMechieetal.2011, author = {Mohsen, Amjad and Asch, G{\"u}nter and Mechie, James and Kind, Rainer and Hofstetter, Rami and Weber, Michael H. and Stiller, M. and Abu-Ayyash, Khalil}, title = {Crustal structure of the Dead Sea Basin (DSB) from a receiver function analysis}, series = {Geophysical journal international}, volume = {184}, journal = {Geophysical journal international}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2010.04853.x}, pages = {463 -- 476}, year = {2011}, abstract = {The Dead Sea Transform (DST) is a major left-lateral strike-slip fault that accommodates the relative motion between the African and Arabian plates, connecting a region of extension in the Red Sea to the Taurus collision zone in Turkey over a length of about 1100 km. The Dead Sea Basin (DSB) is one of the largest basins along the DST. The DSB is a morphotectonic depression along the DST, divided into a northern and a southern sub-basin, separated by the Lisan salt diapir. We report on a receiver function study of the crust within the multidisciplinary geophysical project, DEad Sea Integrated REsearch (DESIRE), to study the crustal structure of the DSB. A temporary seismic network was operated on both sides of the DSB between 2006 October and 2008 April. The aperture of the network is approximately 60 km in the E-W direction crossing the DSB on the Lisan peninsula and about 100 km in the N-S direction. Analysis of receiver functions from the DESIRE temporary network indicates that Moho depths vary between 30 and 38 km beneath the area. These Moho depth estimates are consistent with results of near-vertical incidence and wide-angle controlled-source techniques. Receiver functions reveal an additional discontinuity in the lower crust, but only in the DSB and west of it. This leads to the conclusion that the internal crustal structure east and west of the DSB is different at the present-day. However, if the 107 km left-lateral movement along the DST is taken into account, then the region beneath the DESIRE array where no lower crustal discontinuity is observed would have lain about 18 Ma ago immediately adjacent to the region under the previous DESERT array west of the DST where no lower crustal discontinuity is recognized.}, language = {en} } @misc{Kallmeyer2011, author = {Kallmeyer, Jens}, title = {Detection and quantification of microbial cells in subsurface sediments}, series = {Advances in applied microbiology}, volume = {76}, journal = {Advances in applied microbiology}, editor = {Laskin, AI and Sariaslani, S and Gadd, GM}, publisher = {Elsevier}, address = {San Diego}, isbn = {978-0-12-387048-3}, issn = {0065-2164}, doi = {10.1016/B978-0-12-387048-3.00003-9}, pages = {79 -- 103}, year = {2011}, abstract = {Quantification of total cell abundance is one of the most fundamental parameters in the exploration of subsurface life. Despite all recent advances in molecular techniques, this parameter is usually determined by fluorescence microscopy. In order to obtain reliable and reproducible results, it is important not just to focus on the actual cell enumeration but also to consider the entire chain of processing. Starting with the retrieval of the sample, over subsampling and sample processing to the final step of fluorescence microscopy, there are many potential sources of contamination that have to be assessed and, if possible, avoided. Because some degree of sample contamination will always occur, it is necessary to employ some form of contamination control. Different tracers are available, each one with its specific advantages and drawbacks. In many cases, the problems arise not after the sample has arrived in a well-equipped laboratory with highly trained personnel, but much earlier at the drill site or in a field camp. In this review, I discuss the different aspects of cell enumeration in subsurface sediment, evaluating every step in the long process chain.}, language = {en} } @article{VargasFariasCarretieretal.2011, author = {Vargas, Gabriel and Farias, Marcelo and Carretier, Sebastien and Tassara, Andres and Baize, Stephane and Melnick, Daniel}, title = {Coastal uplift and tsunami effects associated to the 2010 M(w)8.8 Maule earthquake in Central Chile}, series = {Andean geology}, volume = {38}, journal = {Andean geology}, number = {1}, publisher = {Servicio Nacional de Geolog{\`i}a y Miner{\`i}a}, address = {Santiago}, issn = {0718-7106}, doi = {10.5027/andgeoV38n1-a12}, pages = {219 -- 238}, year = {2011}, abstract = {On February 27, 2010 at 03:34:08 AM an M(w)8.8 earthquake, with epicenter located off Cobquecura (73.24 degrees W; 36.29 degrees S), severely hit Central Chile. The tsunami waves that followed this event affected the coastal regions between the cities of Valparaiso and Valdivia, with minor effects as far as Coquimbo. The earthquake occurred along the subduction of the Nazca oceanic plate beneath the South American plate. Coseismic coastal uplift was estimated through observations of bleached lithothamnioids crustose coralline algae, which were exposed after the mainshock between 34.13 degrees S and 38.34 degrees S, suggesting the latitudinal distribution of the earthquake rupture. The measured coastal uplift values varied between 240 +/- 20 cm at sites closer to the trench along the western coast of the Arauco peninsula and 15 +/- 10 cm at sites located farther east. A maximum value of 260 +/- 50 cm was observed at the western coast of Santa Maria Island, which is similar to the reported uplift associated with the 1835 earthquake at Concepcion. Land subsidence values on the order of 0.5 m to 1 m evidenced a change in polarity and position of the coseismic hinge at 110-120 km from the trench. In four sites along the coast we observed a close match between coastal uplift values deduced from bleached lithothamnioids algae and GPS measurements. According to field observations tsunami heights reached ea. 14 m in the coastal area of the Maule Region immediately north of the epicenter, and diminished progressively northwards to 4-2 m near Valparaiso. Along the coast of Cobquecura, tsunami height values were inferior to 2-4 m. More variable tsunami heights of 6-8 m were measured at Dichato-Talcahuano and Tirua-Puerto Saavedra, in the Biobio and Arauco regions, respectively, to the south of the epicenter. According to eyewitnesses, the tsunami reached the coast between 12 to 20 and 30 to 45 minutes in areas located closer and faraway from the earthquake rupture zone, respectively. Destructive tsunami waves arrived also between 2.5 and 4.5 hours after the mainshock, especially along the coast of the Biobio and Arauco regions. The tsunami effects were highly variable along the coast, as a result of geomorphological and bathymetric local conditions, besides potential complexities induced by the main shock.}, language = {en} } @article{SakiMoazzenOberhaensli2011, author = {Saki, A. and Moazzen, Mohssen and Oberh{\"a}nsli, Roland}, title = {P-T evolution of the precambrian metamorphic complex, NW Iran a study of metapelitic rocks}, series = {Geological journal}, volume = {46}, journal = {Geological journal}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0072-1050}, doi = {10.1002/gj.1236}, pages = {10 -- 25}, year = {2011}, abstract = {The Mahneshan Metamorphic Complex (MMC) is one of the Precambrian terrains exposed in the northwest of Iran. The MMC underwent two main phases of deformation (D-1 and D-2) and at least two metamorphic events (M-1 and M-2). Critical metamorphic mineral assemblages in the metapelitic rocks testify to regional metamorphism under amphibolite-facies conditions. The dominant metamorphic mineral assemblage in metapelitic rocks (M-1) is muscovite, biotite I, Garnet I, staurolite, Andalusite I and sillimanite. Peak metamorphism took place at 600-620 degrees C and similar to 7 kbar, corresponding to a depth of ca. 24 km. This was followed by decompression during exhumation of the crustal rocks up to the surface. The decrease of temperature and pressure during exhumation produced retrograde metamorphic assemblages (M-2). Secondary phases such as garnet II biotite It. Andalusite II constrain the temperature and pressure of M, retrograde metamorphism to 520-560 degrees C and 2.5-3.5 kbar, respectively. The geothermal gradient obtained for the peak of metamorphism is 33 degrees C km(-1), which indicates that peak metamorphism was of Barrovian type and occurred under medium-pressure conditions. The MMC followed a 'clockwise' P T path during metamorphism, consistent with thermal relaxation following tectonic thickening. The bulk chemistry of the MMC metapelites shows that their protoliths were deposited at an active continental margin. Together with the presence of palaeo-suture zones and ophiolitic rocks around the high-grade metamorphic rocks of the MMC, these features suggest that the Iranian Precambrian basement formed by an island-arc type cratonization.}, language = {en} } @article{CandanKoralayAkaletal.2011, author = {Candan, Osman and Koralay, O. E. and Akal, Cemal B. and Kaya, O. and Oberh{\"a}nsli, Roland and Dora, O. O. and Konak, N. and Chen, F.}, title = {Supra-Pan-African unconformity between core and cover series of the Menderes Massif/Turkey and its geological implications}, series = {Precambrian research}, volume = {184}, journal = {Precambrian research}, number = {1-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-9268}, doi = {10.1016/j.precamres.2010.09.010}, pages = {1 -- 23}, year = {2011}, abstract = {Well-preserved primary contact relationships between a Late Proterozoic metasedimentary and the metagranitic core and Palaeozoic cover series of the Menderes Massif have been recognized in the eastern part of the Cine submassif on a regional-scale. Metaconglomerates occur as laterally discontinuous channel-fill bodies close the base of the metaquartzarenite directly above the basement. The pebbles in the metaconglomerates consist mainly of different types of tourmaline-rich leucocratic granitoids, tourmalinite and schist in a sandy matrix. Petrographic features, geochemical compositions and zircon radiometric ages (549.6 +/- 3.7-552.3 +/- 3.1 Ma) of the diagnostic clasts of the metaconglomerates (e.g. leucocratic granitoids and tourmalinites) show excellent agreement with their in situ equivalents (549.0 +/- 5.4 Ma) occurring in the Pan-African basement as stocks and veins. The correlation between clasts in the metaconglomerates and granitoids of the basement suggests that the primary contact between the basement and cover series is a regional unconformity (supra-Pan-African Unconformity) representing deep erosion of the Pan-African basement followed by the deposition of the cover series. Hence the usage of 'core-cover' terminology in the Menderes Massif is valid. Consequently, these new data preclude the views that the granitic precursors of the leucocratic orthogneisses are Tertiary intrusions.}, language = {en} } @article{PanetKuroishiHolschneider2011, author = {Panet, Isabelle and Kuroishi, Yuki and Holschneider, Matthias}, title = {Wavelet modelling of the gravity field by domain decomposition methods: an example over Japan}, series = {Geophysical journal international}, volume = {184}, journal = {Geophysical journal international}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2010.04840.x}, pages = {203 -- 219}, year = {2011}, abstract = {With the advent of satellite gravity, large gravity data sets of unprecedented quality at low and medium resolution become available. For local, high resolution field modelling, they need to be combined with the surface gravity data. Such models are then used for various applications, from the study of the Earth interior to the determination of oceanic currents. Here we show how to realize such a combination in a flexible way using spherical wavelets and applying a domain decomposition approach. This iterative method, based on the Schwarz algorithms, allows to split a large problem into smaller ones, and avoids the calculation of the entire normal system, which may be huge if high resolution is sought over wide areas. A subdomain is defined as the harmonic space spanned by a subset of the wavelet family. Based on the localization properties of the wavelets in space and frequency, we define hierarchical subdomains of wavelets at different scales. On each scale, blocks of subdomains are defined by using a tailored spatial splitting of the area. The data weighting and regularization are iteratively adjusted for the subdomains, which allows to handle heterogeneity in the data quality or the gravity variations. Different levels of approximations of the subdomains normals are also introduced, corresponding to building local averages of the data at different resolution levels. We first provide the theoretical background on domain decomposition methods. Then, we validate the method with synthetic data, considering two kinds of noise: white noise and coloured noise. We then apply the method to data over Japan, where we combine a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoid is obtained at about 15 km resolution and a corrector grid for the surface model is derived.}, language = {en} } @article{DanielPronoRenardetal.2011, author = {Daniel, G. and Prono, E. and Renard, F. and Thouvenot, F. and Hainzl, Sebastian and Marsan, D. and Helmstetter, A. and Traversa, P. and Got, J. L. and Jenatton, L. and Guiguet, R.}, title = {Changes in effective stress during the 2003-2004 Ubaye seismic swarm, France}, series = {Journal of geophysical research : Solid earth}, volume = {116}, journal = {Journal of geophysical research : Solid earth}, number = {4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1029/2010JB007551}, pages = {13}, year = {2011}, abstract = {We study changes in effective stress (normal stress minus pore pressure) that occurred in the French Alps during the 2003-2004 Ubaye earthquake swarm. Two complementary data sets are used. First, a set of 974 relocated events allows us to finely characterize the shape of the seismogenic area and the spatial migration of seismicity during the crisis. Relocations are performed by a double-difference algorithm. We compute differences in travel times at stations both from absolute picking times and from cross-correlation delays of multiplets. The resulting catalog reveals a swarm alignment along a single planar structure striking N130 degrees E and dipping 80 degrees W. This relocated activity displays migration properties consistent with a triggering by a diffusive fluid overpressure front. This observation argues in favor of a deep-seated fluid circulation responsible for a significant part of the seismic activity in Ubaye. Second, we analyze time series of earthquake detections at a single seismological station located just above the swarm. This time series forms a dense chronicle of +16,000 events. We use it to estimate the history of effective stress changes during this sequence. For this purpose we model the rate of events by a stochastic epidemic-type aftershock sequence model with a nonstationary background seismic rate lambda(0)(t). This background rate is estimated in discrete time windows. Window lengths are determined optimally according to a new change-point method on the basis of the interevent times distribution. We propose that background events are triggered directly by a transient fluid circulation at depth. Then, using rate-and-state constitutive friction laws, we estimate changes in effective stress for the observed rate of background events. We assume that changes in effective stress occurred under constant shear stressing rate conditions. We finally obtain a maximum change in effective stress close to -8 MPa, which corresponds to a maximum fluid overpressure of about 8 MPa under constant normal stress conditions. This estimate is in good agreement with values obtained from numerical modeling of fluid flow at depth, or with direct measurements reported from fluid injection experiments.}, language = {en} } @phdthesis{Olaka2011, author = {Olaka, Lydia Atieno}, title = {Hydrology across scales : sensitivity of East African lakes to climate changes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55029}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The lakes of the East African Rift System (EARS) have been intensively studied to better understand the influence of climate change on hydrological systems. The exceptional sensitivity of these rift lakes, however, is both a challenge and an opportunity when trying to reconstruct past climate changes from changes in the hydrological budget of lake basins on timescales 100 to 104 years. On one hand, differences in basin geometrics (shape, area, volume, depth), catchment rainfall distributions and varying erosion-deposition rates complicate regional interpretation of paleoclimate information from lacustrine sediment proxies. On the other hand, the sensitivity of rift lakes often provides paleoclimate records of excellent quality characterized by a high signal-to-noise ratio. This study aims at better understanding of the climate-proxy generating process in rift lakes by parameterizing the geomorphological and hydroclimatic conditions of a particular site providing a step towards the establishment of regional calibrations of transfer functions for climate reconstructions. The knowledge of the sensitivity of a lake basin to climate change furthermore is crucial for a better assessment of the probability of catastrophic changes in the future, which bear risks for landscapes, ecosystems, and organisms of all sorts, including humans. Part 1 of this thesis explores the effect of the morphology and the effective moisture of a lake catchment. The availability of digital elevation models (DEM) and gridded climate data sets facilitates the comparison of the morphological and hydroclimatic conditions of rift lakes. I used the hypsometric integral (HI) calculated from Shuttle Radar Topography Mission (SRTM) data to describe the morphology of ten lake basins in Kenya and Ethiopia. The aridity index (AI) describing the difference in the precipitation/evaporation balance within a catchment was used to compare the hydroclimatic of these basins. Correlating HI and AI with published Holocene lake-level variations revealed that lakes responding sensitively to relatively moderate climate change are typically graben shaped and characterized by a HI between 0.23-0.30, and relatively humid conditions with AI >1. These amplifier lakes, a term first introduced but not fully parameterized by Alayne Street-Perrott in the early 80s, are unexceptionally located in the crest of the Kenyan and Ethiopian domes. The non-amplifier lakes in the EARS either have lower HI 0.13-0.22 and higher AI (>1) or higher HI (0.31-0.37) and low AI (<1), reflecting pan-shaped morphologies with more arid hydroclimatic conditions. Part 2 of this work addresses the third important factor to be considered when using lake-level and proxy records to unravel past climate changes in the EARS: interbasin connectivity and groundwater flow through faulted and porous subsurface lithologies in a rift setting. First, I have compiled the available hydrogeological data including lithology, resistivity and water-well data for the adjacent Naivasha and Elmenteita-Nakuru basins in the Central Kenya Rift. Using this subsurface information and established records of lake-level decline at the last wet-dry climate transitions, i.e., the termination of the African Humid Period (AHP, 15 to 5 kyr BP), I used a linear decay model to estimate typical groundwater flow between the two basins. The results suggest a delayed response of the groundwater levels of ca. 5 kyrs if no recharge of groundwater occurs during the wet-dry transition, whereas the lag is 2-2.7 kyrs only using the modern recharge of ca. 0.52 m/yr. The estimated total groundwater flow from higher Lake Naivasha (1,880 m a.s.l. during the AHP) to Nakuru-Elmenteita (1,770 m) was 40 cubic kilometers. The unexpectedly large volume, more than half of the volume of the paleo-Lake Naivasha during the Early Holocene, emphasizes the importance of groundwater in hydrological modeling of paleo-lakes in rifts. Moreover, the subsurface connectivity of rift lakes also causes a significant lag time to the system introducing a nonlinear component to the system that has to be considered while interpreting paleo-lake records. Part 3 of this thesis investigated the modern intraseasonal precipitation variability within eleven lake basins discussed in the first section of the study excluding Lake Victoria and including Lake Tana. Remotely sensed rainfall estimates (RFE) from FEWS NET for 1996-2010, are used for the, March April May (MAM) July August September (JAS), October November (ON) and December January February (DJF). The seasonal precipitation are averaged and correlated with the prevailing regional and local climatic mechanisms. Results show high variability with Biennial to Triennial precipitation patterns. The spatial distribution of precipitation in JAS are linked to the onset and strength of the Congo Air Boundary (CAB) and Indian Summer Monsoon (ISM) dynamics. while in ON they are related to the strength of Positive ENSO and IOD phases This study describes the influence of graben morphologies, extreme climate constrasts within catchments and basins connectivity through faults and porous lithologies on rift lakes. Hence, it shows the importance of a careful characterization of a rift lake by these parameters prior to concluding from lake-level and proxy records to climate changes. Furthermore, this study highlights the exceptional sensitivity of rift lakes to relatively moderate climate change and its consequences for water availability to the biosphere including humans.}, language = {en} } @article{KielingRoesslerKrueger2011, author = {Kieling, Katrin and R{\"o}ßler, Dirk and Kr{\"u}ger, Frank}, title = {Receiver function study in northern Sumatra and the Malaysian peninsula}, series = {Journal of seismology}, volume = {15}, journal = {Journal of seismology}, number = {2}, publisher = {Springer}, address = {Dordrecht}, issn = {1383-4649}, doi = {10.1007/s10950-010-9222-7}, pages = {235 -- 259}, year = {2011}, abstract = {In this receiver function study, we investigate the structure of the crust beneath six seismic broadband stations close to the Sunda Arc formed by subduction of the Indo-Australian under the Sunda plate. We apply three different methods to analyse receiver functions at single stations. A recently developed algorithm determines absolute shear-wave velocities from observed frequency-dependent apparent incidence angles of P waves. Using waveform inversion of receiver functions and a modified Zhu and Kanamori algorithm, properties of discontinuities such as depth, velocity contrast, and sharpness are determined. The combination of the methods leads to robust results. The approach is validated by synthetic tests. Stations located on Malaysia show high-shear-wave velocities (V (S)) near the surface in the range of 3.4-3.6 km s (-aEuro parts per thousand 1) attributed to crystalline rocks and 3.6-4.0 km s (-aEuro parts per thousand 1) in the lower crust. Upper and lower crust are clearly separated, the Moho is found at normal depths of 30-34 km where it forms a sharp discontinuity at station KUM or a gradient at stations IPM and KOM. For stations close to the subduction zone (BSI, GSI and PSI) complexity within the crust is high. Near the surface low V (S) of 2.6-2.9 km s (-aEuro parts per thousand 1) indicate sediment layers. High V (S) of 4.2 km s (-aEuro parts per thousand 1) are found at depth greater than 6 and 2 km at BSI and PSI, respectively. There, the Moho is located at 37 and 40 km depth. At station GSI, situated closest to the trench, the subducting slab is imaged as a north-east dipping structure separated from the sediment layer by a 10 km wide gradient in V (S) between 10 and 20 km depth. Within the subducting slab V (S) a parts per thousand aEuro parts per thousand 4.7 km s (-aEuro parts per thousand 1). At station BSI, the subducting slab is found at depth between 90 and 110 km dipping 20A degrees +/- 8A degrees in approximately N 60A degrees E. A velocity increase in similar depth is indicated at station PSI, however no evidence for a dipping layer is found.}, language = {en} } @article{CzubaGradMjeldeetal.2011, author = {Czuba, Wojciech and Grad, Marek and Mjelde, Rolf and Guterch, Aleksander and Libak, Audun and Kr{\"u}ger, Frank and Murai, Yoshio and Schweitzer, Johannes}, title = {Continent-ocean-transition across a trans-tensional margin segment: off Bear Island, Barents Sea}, series = {Geophysical journal international}, volume = {184}, journal = {Geophysical journal international}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, organization = {IPY Project Grp}, issn = {0956-540X}, doi = {10.1111/j.1365-246X.2010.04873.x}, pages = {541 -- 554}, year = {2011}, abstract = {P>A 410 km long Ocean Bottom Seismometer profile spanning from the Bear Island, Barents Sea to oceanic crust formed along the Mohns Ridge has been modelled by use of ray-tracing with regard to observed P-waves. The northeastern part of the model represents typical continental crust, thinned from ca. 30 km thickness beneath the Bear Island to ca. 13 km within the Continent-Ocean-Transition. Between the Hornsund FZ and the Kn circle divide legga Fault, a 3-4 km thick sedimentary basin, dominantly of Permian/Carboniferous age, is modelled beneath the ca. 1.5 km thick layer of volcanics (Vestbakken Volcanic Province). The P-wave velocity in the 3-4 km thick lowermost continental crust is significantly higher than normal (ca. 7.5 km s-1). We interpret this layer as a mixture of mafic intrusions and continental crystalline blocks, dominantly related to the Paleocene-Early Eocene rifting event. The crystalline portion of the crust within the south-western part of the COT consists of a ca. 30 km wide and ca. 6 km thick high-velocity (7.3 km s-1) body. We interpret the body as a ridge of serpentinized peridotites. The magmatic portion of the ocean crust accreted along the Knipovich Ridge from continental break-up at ca. 35 Ma until ca. 20 Ma is 3-5 km thicker than normal. We interpret the increased magmatism as a passive response to the bending of this southernmost part of the Knipovich Ridge. The thickness of the magmatic portion of the crust formed along the Mohns Ridge at ca. 20 Ma decreases to ca. 3 km, which is normal for ultra slow spreading ridges.}, language = {en} } @article{NaafsHefterFerrettietal.2011, author = {Naafs, B. David A. and Hefter, Jens and Ferretti, Patrizia and Stein, R{\"u}diger and Haug, Gerald H.}, title = {Sea surface temperatures did not control the first occurrence of Hudson Strait Heinrich Events during MIS 16}, series = {Paleoceanography}, volume = {26}, journal = {Paleoceanography}, number = {4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0883-8305}, doi = {10.1029/2011PA002135}, pages = {10}, year = {2011}, abstract = {Hudson Strait (HS) Heinrich Events, ice-rafting events in the North Atlantic originating from the Laurentide ice sheet (LIS), are among the most dramatic examples of millennial-scale climate variability and have a large influence on global climate. However, it is debated as to whether the occurrence of HS Heinrich Events in the (eastern) North Atlantic in the geological record depends on greater ice discharge, or simply from the longer survival of icebergs in cold waters. Using sediments from Integrated Ocean Drilling Program (IODP) Site U1313 in the North Atlantic spanning the period between 960 and 320 ka, we show that sea surface temperatures (SSTs) did not control the first occurrence of HS Heinrich(-like) Events in the sedimentary record. Using mineralogy and organic geochemistry to determine the characteristics of ice-rafting debris (IRD), we detect the first HS Heinrich(-like) Event in our record around 643 ka (Marine Isotope Stage (MIS) 16), which is similar as previously reported for Site U1308. However, the accompanying high-resolution alkenone-based SST record demonstrates that the first HS Heinrich(-like) Event did not coincide with low SSTs. Thus, the HS Heinrich(-like) Events do indicate enhanced ice discharge from the LIS at the end of the Mid-Pleistocene Transition, not simply the survivability of icebergs due to cold conditions in the North Atlantic.}, language = {en} } @article{FaderGertenThammeretal.2011, author = {Fader, Marianelle and Gerten, Dieter and Thammer, M. and Heinke, J. and Lotze-Campen, Hermann and Lucht, Wolfgang and Cramer, Wolfgang}, title = {Internal and external green-blue agricultural water footprints of nations, and related water and land savings through trade}, series = {Hydrology and earth system sciences : HESS}, volume = {15}, journal = {Hydrology and earth system sciences : HESS}, number = {5}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-15-1641-2011}, pages = {1641 -- 1660}, year = {2011}, abstract = {The need to increase food production for a growing world population makes an assessment of global agricultural water productivities and virtual water flows important. Using the hydrology and agro-biosphere model LPJmL, we quantify at 0.5 degrees resolution the amount of blue and green water (irrigation and precipitation water) needed to produce one unit of crop yield, for 11 of the world's major crop types. Based on these, we also quantify the agricultural water footprints (WFP) of all countries, for the period 1998-2002, distinguishing internal and external WFP (virtual water imported from other countries) and their blue and green components, respectively. Moreover, we calculate water savings and losses, and for the first time also land savings and losses, through international trade with these products. The consistent separation of blue and green water flows and footprints shows that green water globally dominates both the internal and external WFP (84\% of the global WFP and 94\% of the external WFP rely on green water). While no country ranks among the top ten with respect to all water footprints calculated here, Pakistan and Iran demonstrate high absolute and per capita blue WFP, and the US and India demonstrate high absolute green and blue WFPs. The external WFPs are relatively small (6\% of the total global blue WFP, 16\% of the total global green WFP). Nevertheless, current trade of the products considered here saves significant water volumes and land areas (similar to 263 km(3) and similar to 41 Mha, respectively, equivalent to 5\% of the sowing area of the considered crops and 3.5\% of the annual precipitation on this area). Relating the proportions of external to internal blue/green WFP to the per capita WFPs allows recognizing that only a few countries consume more water from abroad than from their own territory and have at the same time above-average WFPs. Thus, countries with high per capita water consumption affect mainly the water availability in their own country. Finally, this study finds that flows/savings of both virtual water and virtual land need to be analysed together, since they are intrinsically related.}, language = {en} } @article{ZhangWielandReicheetal.2011, author = {Zhang, Zhuodong and Wieland, Ralf and Reiche, Matthias and Funk, Roger and Hoffmann, Carsten and Li, Yong and Sommer, Michael}, title = {Wind modelling for wind erosion research by open source computational fluid dynamics}, series = {Ecological informatics : an international journal on ecoinformatics and computational ecolog}, volume = {6}, journal = {Ecological informatics : an international journal on ecoinformatics and computational ecolog}, number = {5}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1574-9541}, doi = {10.1016/j.ecoinf.2011.02.001}, pages = {316 -- 324}, year = {2011}, abstract = {The open source computational fluid dynamics (CFD) wind model (CFD-WEM) for wind erosion research in the Xilingele grassland in Inner Mongolia (autonomous region, China) is compared with two open source CFD models Gerris and OpenFOAM. The evaluation of these models was made according to software technology, implemented methods, handling, accuracy and calculation speed. All models were applied to the same wind tunnel data set. Results show that the simplest CFD-WEM has the highest calculation speed with acceptable accuracy, and the most powerful OpenFOAM produces the simulation with highest accuracy and the lowest calculation speed. Gerris is between CFD-WEM and OpenFOAM. It calculates faster than OpenFOAM, and it is capable to solve different CFD problems. CFD-WEM is the optimal model to be further developed for wind erosion research in Inner Mongolia grassland considering its efficiency and the uncertainties of other input data. However, for other applications using CFD technology, Gerris and OpenFOAM can be good choices. This paper shows the powerful capability of open source CFD software in wind erosion study, and advocates more involvement of open source technology in wind erosion and related ecological researches.}, language = {en} } @article{GuzmanPetrinovicBrodetal.2011, author = {Guzman, S. and Petrinovic, I. A. and Brod, J. A. and Hongn, Fernando D. and Seggiaro, R. E. and Montero, C. and Carniel, Roberto and Dantas, E. L. and Sudo, Masafumi}, title = {Petrology of the Luingo caldera (SE margin of the Puna plateau) a middle Miocene window of the arc-back arc configuration}, series = {Journal of volcanology and geothermal research}, volume = {200}, journal = {Journal of volcanology and geothermal research}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0377-0273}, doi = {10.1016/j.jvolgeores.2010.12.008}, pages = {171 -- 191}, year = {2011}, abstract = {We describe the petrographic characteristics, whole-rock geochemistry and mineral chemistry of rocks from the Pucarilla-Cerro Tipillas Volcanic Complex with emphasis on the rocks belonging to the middle Miocene Luingo caldera, located in the south-eastern portion of the Central Volcanic Zone (CVZ) of the Andes. We modelled the petrogenesis of the Luingo caldera rocks as a mixture of ca. 20\% crustal magmas and 80\% of mantle magmas by AFC with recharge processes. A comparison of Luingo geochemical data with the composition of Miocene-Pliocene volcanic rocks from the broad area, points to major thickening events during the middle Miocene for the western portion and during the upper Miocene for the eastern portion of the Southern CVZ. In the eastern sector (similar to 66 degrees W) the mantle source appears to change from a spinel-lherzolite type for the middle Miocene to a garnet-lherzolite type for the upper Miocene-Pliocene magmas. The areal distribution of the volcanic products led to the recognition of approximately equivalent areas covered by volcanic rocks both in the eastern and in the western Puna borders. This indicates a broad arc, which was structurally controlled at the proto-Puna/Puna margins, whose geochemical differences are related with variations in crustal thicknesses and heterogeneous mantle sources from west to east.}, language = {en} } @article{WillnerGerdesMassonneetal.2011, author = {Willner, Arne P. and Gerdes, Axel and Massonne, Hans-Joachim and Schmidt, Alexander and Sudo, Masafumi and Thomson, Stuart N. and Vujovich, Graciela}, title = {The geodynamics of collision of a microplate (Chilenia) in Devonian times deduced by the pressure-temperature-time evolution within part of a collisional belt (Guarguaraz Complex, W-Argentina)}, series = {Contributions to mineralogy and petrology}, volume = {162}, journal = {Contributions to mineralogy and petrology}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0010-7999}, doi = {10.1007/s00410-010-0598-8}, pages = {303 -- 327}, year = {2011}, abstract = {The Guarguaraz Complex in West Argentina formed during collision between the microplate Chilenia and South America. It is composed of neritic clastic metasediments with intercalations of metabasic and ultrabasic rocks of oceanic origin. Prograde garnet growth in metapelite and metabasite occurred between 1.2 GPa, 470 degrees C and 1.4 GPa, 530 degrees C, when the penetrative s(2)-foliation was formed. The average age of garnet crystallization of 390 +/- 2 Ma (2 sigma) was determined from three four-point Lu-Hf mineral isochrones from metapelite and metabasite samples and represents the time of collision. Peak pressure conditions are followed by a decompression path with slight heating at 0.5 GPa, 560 degrees C. Fluid release during decompression caused equilibration of mineral compositions at the rims and also aided Ar diffusion. An Ar-40/39 Ar plateau age of white mica at 353 +/- 1 Ma (1 sigma) indicates the time of cooling below 350-400 degrees C. These temperatures were attained at pressures of 0.2-0.3 GPa, indicative of an average exhumation rate of >= 1 mm/a for the period 390-353 Ma. Late hydrous influx at 0.1-0.3 GPa caused pervasive growth of sericite and chlorite and reset the Ar/Ar ages of earlier coarse-grained white mica. At 284-295 Ma, the entire basement cooled below 280 degrees C (fission track ages of zircon) after abundant post-collisional granitoid intrusion. The deeply buried epicontinental sedimentary rocks, the high peak pressure referring to a low metamorphic geotherm of 10-12 degrees C/km, and the decompression/heating path are characteristics of material buried and exhumed within a (micro) continent-continent collisional setting.}, language = {en} } @article{BallatoUbaLandgrafetal.2011, author = {Ballato, Paolo and Uba, Cornelius Eji and Landgraf, Angela and Strecker, Manfred and Sudo, Masafumi and Stockli, Daniel F. and Friedrich, Anke M. and Tabatabaei, Saeid H.}, title = {Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran}, series = {Geological Society of America bulletin}, volume = {123}, journal = {Geological Society of America bulletin}, number = {1-2}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0016-7606}, doi = {10.1130/B30091.1}, pages = {106 -- 131}, year = {2011}, abstract = {A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone.}, language = {en} } @article{DeekenThiedeSobeletal.2011, author = {Deeken, Anke and Thiede, Rasmus Christoph and Sobel, Edward and Hourigan, J. K. and Strecker, Manfred}, title = {Exhumational variability within the Himalaya of northwest India}, series = {Earth \& planetary science letters}, volume = {305}, journal = {Earth \& planetary science letters}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2011.02.045}, pages = {103 -- 114}, year = {2011}, abstract = {In the Himalaya of Chamba, NW India, a major orographic barrier in front of the Greater Himalayan Range extracts a high proportion of the monsoonal rainfall along its southern slopes and effectively shields the orogen interior from moisture-bearing winds. Along a similar to 100-km-long orogen perpendicular transect, 28 new apatite fission track (AFT) and 30 new zircon (U-Th)/He (ZHe) cooling ages reveal marked variations in age distributions and long-term exhumation rates between the humid frontal range and the semi-arid orogen interior. On the southern topographic front, very young, elevation-invariant AFT ages of <4 Ma have been obtained that are concentrated in a similar to 30-km-wide zone; 1-D-thermal modeling suggests a Plio-Pleistocene mean erosion rate of 0.8-1.9 mm yr(-1). In contrast, AFT and ZHe ages within the orogen interior are older (4-9 and 7-18 Ma, respectively), are positively correlated with sample elevation, and yield lower mean erosion rates (0.3-0.9 mm yr(-1)). Protracted low exhumation rates within the orogen interior over the last similar to 15 Myr prevailed contemporaneously with overall humid conditions and an effective erosional regime within the southern Himalaya. This suggests that the frontal Dhauladar Range was sufficiently high during this time to form an orographic barrier, focusing climatically enhanced erosional processes and tectonic deformation there. Thrusting along the two frontal range-bounding thrust, the Main Central Thrust and the Main Boundary Thrusts, was initiated at least similar to 15 Ma ago and has remained localized since then. The lack of evidence for localized uplift farther north indicates either a rather flat decollement with no ramp or the absence of active duplex systems beneath the interior of Chamba. Exhumational variability within Chamba is best explained as the result of continuous thrusting along a major basal decollement, with a flat beneath the slowly exhuming internal compartments and a steep frontal ramp at the rapidly exhuming frontal range. The pattern in Chamba contrasts with what is observed elsewhere along the Himalaya, where exhumation is focused in a zone similar to 150 km north of the orogenic front. In the NW Himalaya, preserved High Himalayan Crystalline nappes and Lesser Himalayan windows alternate on a relatively small scale of <100 km; these alternations are closely correlated with the pattern of exhumation. Although the spatial distribution of high-exhumation zones varies considerably between individual Himalayan sectors, all of these zones are closely correlated with locally higher rock-uplift rates, sharp topographic discontinuities, and focused orographic precipitation, suggesting strong feedbacks between tectonically driven rock uplift, orographically enhanced precipitation, and erosional processes.}, language = {en} } @article{AlbrechtMartinHaseloffetal.2011, author = {Albrecht, Tanja and Martin, M. and Haseloff, M. and Winkelmann, Ricarda and Levermann, Anders}, title = {Parameterization for subgrid-scale motion of ice-shelf calving fronts}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {5}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {1}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-5-35-2011}, pages = {35 -- 44}, year = {2011}, abstract = {A parameterization for the motion of ice-shelf fronts on a Cartesian grid in finite-difference land-ice models is presented. The scheme prevents artificial thinning of the ice shelf at its edge, which occurs due to the finite resolution of the model. The intuitive numerical implementation diminishes numerical dispersion at the ice front and enables the application of physical boundary conditions to improve the calculation of stress and velocity fields throughout the ice-sheet-shelf system. Numerical properties of this subgrid modification are assessed in the Potsdam Parallel Ice Sheet Model (PISM-PIK) for different geometries in one and two horizontal dimensions and are verified against an analytical solution in a flow-line setup.}, language = {en} }