TY  - JOUR
A1  - Aichner, Bernhard
A1  - Hilt, Sabine
A1  - Perillon, Cecile
A1  - Gillefalk, Mikael
A1  - Sachse, Dirk
T1  - Biosynthetic hydrogen isotopic fractionation factors during lipid synthesis in submerged aquatic macrophytes: Effect of groundwater discharge and salinity
JF  - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
N2  - Sedimentary lipid biomarkers have become widely used tools for reconstructing past climatic and ecological changes due to their ubiquitous occurrence in lake sediments. In particular, the hydrogen isotopic composition (expressed as delta D values) of leaf wax lipids derived from terrestrial plants has been a focus of research during the last two decades and the understanding of competing environmental and plant physiological factors influencing the delta D values has greatly improved. Comparatively less attention has been paid to lipid biomarkers derived from aquatic plants, although these compounds are abundant in many lacustrine sediments. We therefore conducted a field and laboratory experiment to study the effect of salinity and groundwater discharge on the isotopic composition of aquatic plant biomarkers. We analyzed samples of the common submerged plant species, Potamogeton pectinatus (sago pondweed), which has a wide geographic distribution and can tolerate high salinity. We tested the effect of groundwater discharge (characterized by more negative delta D values relative to lake water) and salinity on the delta D values of n-alkanes from P. pectinatus by comparing plants (i) collected from the oligotrophic freshwater Lake Stechlin (Germany) at shallow littoral depth from locations with and without groundwater discharge, and (ii) plants grown from tubers collected from the eutrophic Lake Muggelsee in nutrient solution at four salinity levels. Isotopically depleted groundwater did not have a significant influence on the delta D values of n-alkanes in Lake Stechlin P. pectinatus and calculated isotopic fractionation factors epsilon(l/w) between lake water and n-alkanes averaged -137 +/- 9%(n-C-23), -136 +/- 7%(n-C-25) and -131 +/- 6%(n-C-27), respectively. Similar epsilon values were calculated for plants from Lake Muggelsee grown in freshwater nutrient solution (-134 +/- 11% for n-C-23), while greater fractionation was observed at increased salinity values of 10 (163 +/- 12%) and 15(-172 +/- 15%). We therefore suggest an average e value of -136 +/- 9% between source water and the major n-alkanes in P. pectinatus grown under freshwater conditions. Our results demonstrate that isotopic fractionation can increase by 30-40% at salinity values 10 and 15. These results could be explained either by inhibited plant growth at higher salinity, or by metabolic adaptation to salt stress that remain to be elucidated. A potential salinity effect on dD values of aquatic lipids requires further examination, since this would impact on the interpretation of downcore isotopic data in paleohydrologic studies. (C) 2017 Elsevier Ltd. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.orggeochem.2017.07.021
SN  - 0146-6380
VL  - 113
SP  - 10
EP  - 16
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Makhmudov, Zafar
A1  - Rajabov, Iljomjon
A1  - Zhang, Qiong
A1  - Pausata, Francesco Salvatore R.
A1  - Werner, Martin
A1  - Heinecke, Liv
A1  - Kuessner, Marie L.
A1  - Feakins, Sarah J.
A1  - Sachse, Dirk
A1  - Mischke, Steffen
T1  - Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period
JF  - Geophysical research letters
N2  - The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.
KW  - climate
KW  - biomarker
KW  - geochemistry
KW  - modelling
KW  - paleoclimate
KW  - hydrology
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL085202
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13972
EP  - 13983
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aiken, John M.
A1  - Aiken, Chastity
A1  - Cotton, Fabrice
T1  - A python library for teaching computation to seismology students
JF  - Seismological research letters
N2  - Python is at the forefront of scientific computation for seismologists and therefore should be introduced to students interested in becoming seismologists. On its own, Python is open source and well designed with extensive libraries. However, Python code can also be executed, visualized, and communicated to others with "Jupyter Notebooks". Thus, Jupyter Notebooks are ideal for teaching students Python and scientific computation. In this article, we designed an openly available Python library and collection of Jupyter Notebooks based on defined scientific computation learning goals for seismology students. The Notebooks cover topics from an introduction to Python to organizing data, earthquake catalog statistics, linear regression, and making maps. Our Python library and collection of Jupyter Notebooks are meant to be used as course materials for an upper-division data analysis course in an Earth Science Department, and the materials were tested in a Probabilistic Seismic Hazard course. However, seismologists or anyone else who is interested in Python for data analysis and map making can use these materials.
Y1  - 2018
U6  - https://doi.org/10.1785/0220170246
SN  - 0895-0695
SN  - 1938-2057
VL  - 89
IS  - 3
SP  - 1165
EP  - 1171
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Akal, Cuneyt
A1  - Koralay, O. Ersin
A1  - Candan, Osman
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
T1  - Geodynamic significance of the early triassic karaburun granitoid (Western Turkey) for the opening history of Neo-Tethys
JF  - Turkish journal of earth sciences = Türk yerbilimleri dergisi
N2  - 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.
KW  - Karaburun
KW  - Neo-Tethys
KW  - Palaeo-Tethys
KW  - diorite
KW  - Triassic
KW  - magmatism
Y1  - 2011
U6  - https://doi.org/10.3906/yer-1008-1
SN  - 1300-0985
VL  - 20
IS  - 3
SP  - 255
EP  - 271
PB  - Tübitak
CY  - Ankara
ER  - 
TY  - JOUR
A1  - Akal, Cüneyt
A1  - Candan, Osman
A1  - Koralay, O. Ersin
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
A1  - Prelevic, Dejan
T1  - Early Triassic potassic volcanism in the Afyon Zone of the Anatolides/Turkey - implications for the rifting of the Neo-Tethys
JF  - International journal of earth sciences
N2  - Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethys, is made up of pre-Mesozoic basement and unconformably overlying Triassic-Early Tertiary cover series. The Afyon Zone contains widespread metavolcanic rocks, which are dominated by rhyolite, dacite, and trachyandesite. They form a distinct volcanic succession, which is separated from the underlying Silurian-Lower Carboniferous metacarbonates and meta-siliciclastics by a regional unconformity. Trachyandesitic metavolcanics are made up of massive lava flows, pyroclastics and epiclastics, less frequently, domes and dikes, which were developed on a deeply eroded subaerial landmass. U/Pb and Pb/Pb zircon geochronology yielded Lower Triassic (similar to 250 Ma) ages, which are interpreted as extrusion age of trachyandesitic volcanics. Based on the stratigraphic, geochronological, and geochemical data, we suggest that these Lower Triassic magmatic rocks represent an extensional tectonic setting on the northern active margin of the Gondwana, which led to the development of the northern branch of the Neo-Tethys.
KW  - Meta-trachyandesite
KW  - Afyon Zone
KW  - Turkey
KW  - Neo-Tethys
KW  - Paleo-tethys
Y1  - 2012
U6  - https://doi.org/10.1007/s00531-011-0654-2
SN  - 1437-3254
VL  - 101
IS  - 1
SP  - 177
EP  - 194
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Al Atik, Linda
A1  - Abrahamson, Norman A.
A1  - Bommer, Julian J.
A1  - Scherbaum, Frank
A1  - Cotton, Fabrice
A1  - Kuehn, Nicolas
T1  - The variability of ground-motion prediction models and its components
Y1  - 2010
UR  - http://srl.geoscienceworld.org/
U6  - https://doi.org/10.1785/gssrl.81.5.794
SN  - 0895-0695
ER  - 
TY  - THES
A1  - Al-Halbouni, Djamil
T1  - Photogrammetry and distinct element geomechanical modelling of sinkholes and large-scale karstic depressions
T1  - Photogrammetrie und geomechanische Diskrete-Elemente-Modellierung von Erdfällen und großskaligen Karstsenken
N2  - Sinkholes and depressions are typical landforms of karst regions. They pose a considerable natural hazard to infrastructure, agriculture, economy and human life in affected areas worldwide. The physio-chemical processes of sinkholes and depression formation are manifold, ranging from dissolution and material erosion in the subsurface to mechanical subsidence/failure of the overburden. This thesis addresses the mechanisms leading to the development of sinkholes and depressions  by using complementary methods: remote sensing, distinct element modelling and near-surface geophysics.

In the first part, detailed information about the (hydro)-geological background, ground structures, morphologies and spatio-temporal development of sinkholes and depressions at a very active karst area at the Dead Sea are derived from satellite image analysis, photogrammetry and geologic field surveys. There, clusters of an increasing number of sinkholes have been developing since the 1980s within large-scale depressions and are distributed over different kinds of surface materials: clayey mud, sandy-gravel alluvium and lacustrine evaporites (salt). The morphology of sinkholes differs depending in which material they form: Sinkholes in sandy-gravel alluvium and salt are generally deeper and narrower than sinkholes in the interbedded evaporite and mud deposits. From repeated aerial surveys, collapse precursory features like small-scale  subsidence, individual holes and cracks are identified in all materials. The analysis sheds light on the ongoing hazardous subsidence process, which is driven by the base-level fall of the Dead Sea and by the dynamic formation of subsurface water channels.

In the second part of this thesis, a novel, 2D distinct element geomechanical modelling approach with the software PFC2D-V5 to simulating individual and multiple cavity growth and sinkhole and large-scale depression development is presented. The approach involves a stepwise material removal technique in void spaces of arbitrarily shaped geometries and is benchmarked by analytical and boundary element method solutions for circular cavities. Simulated compression and tension tests are used to calibrate model parameters with bulk rock properties for the materials of the field site. The simulations show that cavity and sinkhole evolution is controlled by material strength of both overburden and cavity host material, the depth and relative speed of the cavity growth and the developed stress pattern in the subsurface. Major findings are: (1) A progressively deepening differential subrosion with variable growth speed yields a more fragmented stress pattern with stress interaction between the cavities. It favours multiple sinkhole collapses and nesting within large-scale depressions. (2) Low-strength materials do not support large cavities in the material removal zone, and subsidence is mainly characterised by gradual sagging into the material removal zone with synclinal bending. (3) High-strength materials support large cavity formation, leading to sinkhole formation by sudden collapse of the overburden. (4) Large-scale depression formation happens either by coalescence of collapsing holes, block-wise brittle failure, or gradual sagging and lateral widening.

The distinct element based approach is compared to results from remote sensing and geophysics at the field site. The numerical simulation outcomes are generally in good agreement with derived morphometrics, documented surface and subsurface structures as well as seismic velocities. Complementary findings on the subrosion process are provided from electric and seismic measurements in the area.

Based on the novel combination of methods in this thesis, a generic model of karst landform evolution with focus on sinkhole and depression formation is developed. A deepening subrosion system related to preferential flow paths evolves and creates void spaces and subsurface conduits. This subsequently leads to hazardous subsidence, and the formation of sinkholes within large-scale depressions. Finally, a monitoring system for shallow natural hazard phenomena consisting of geodetic and geophysical observations is proposed for similarly affected areas.
N2  - Dolinen und Senken sind typische Landformen von Karstgebieten. Sie stellen in den betroffenen Gebieten weltweit ein erhebliches Naturrisiko für Infrastruktur, Landwirtschaft, Wirtschaft und das menschliche Leben dar. Die physikalisch-chemischen Prozesse der Entstehung solcher Senkungen sind vielfältig und reichen von Auflösung und Materialerosion im Untergrund bis zu mechanischem Absenken/Bruchs des Oberbodens. Diese Arbeit betrachtet die Mechanismen, die zur Entwicklung von Dolinen und Senken führen, anhand von verschiedenen geowissenschaftlichen Methoden:Fernerkundung, Gesteinsmechanischer Modellierung und pberflächennaher Geophysik.

Im ersten Teil werden detaillierte Informationen über den geologischen Hintergrund, Bodenstrukturen, Formen und die räumlich-zeitliche Entwicklung von Senkungen an einem sehr aktiven Karstgebiet am Toten Meer zusammengetragen. Dort bilden sich seit den 1980er Jahren immer größere Ansammlungen von Erdfällen, wie diese Phänomene auch oft genannt werden. Die Form der Erdfälle unterscheidet sich je nach Material, in dem sie entstehen: Erdfälle in Sand-Kies Böden und Salz sind im Allgemeinen tiefer und schmaler als Dolinen in den Schlammablagerungen des Toten Meeres. Wiederholte Aufnahmen aus der Luft mit Hilfe von Drohnen oder Ballons helfen dabei, kleine Absenkungen, einzelne Löcher und Risse zu identifizieren. Die Ursache dieser gefährlichen Absenkungen am Toten Meer ist in dem stetigen Fall des Seespiegels und der Bildung von starken Unterwasserkanälen zu sehen, die fortlaufend Material aus dem Boden herausspülen, sog. Subrosion.

Im zweiten Teil dieser Dissertation wird ein neuer, geomechanischer Modellierungsansatz zur Simulation des Wachstums von Hohlräumen im Untergrund und der Bildung von Senkungsstrukturen vorgestellt. Die Simulationen zeigen, dass die Entwicklung der Hohlräume und Erdfälle durch die Materialstärke, die Tiefe und Geschwindigkeit des Hohlraumwachstums und durch das sich bildende Spannungsmuster im Untergrund gesteuert wird. Die wichtigsten Ergebnisse der Studie sind: (1) Eine fortlaufend sich vertiefende Subrosion mit variabler Wachstumsgeschwindigkeit führt zu einem stärker fragmentierten Spannungsmuster im Boden. Es begünstigt das Bilden von ineinander verschachtelten Erdfällen (Cluster) in großen Vertiefungen. (2) Materialien mit niedriger Festigkeit (wie z.B. Schlamm) können keine großen Hohlräume bilden, und das Absinken geschieht durch ein allmähliches Absacken. (3) Materialien mit hoher Festigkeit (wie z.B. verfestigte Sande/Kiese oder Steinsalz) unterstützen die Bildung großer Hohlräume, was zu einem plötzlichen Zusammenbruch des Oberbodens führen kann. (4) Großskalige Senkungsstrukturen bilden sich entweder durch das Verschachteln von kleineren Dolinen, blockweise sprödem Versagen, oder das allmähliche Absinken mit seitlicher Erweiterung.

Die Ergebnisse der numerischen Simulationen stimmen im Allgemeinen sehr gut sowohl mit den beobachteten Senkungsformen an der Oberfläche überein, als auch mit Untergrundstrukturen beobachtet durch seismische und elektrische Methoden. Basierend auf der neuartigen Methodenkombination dieser Arbeit wird ein generisches Modell der Entwicklung von Senkungsstrukturen in Karstgebieten vorgestellt. Eine sich vertiefende Subrosion entlang von unterirdischen Kanälen erzeugt Hohlräume und führt in der Folge zu diesen gefährlichen Absenkungen und zur Bildung von Erdfällen innerhalb großer Vertiefungen.
KW  - Photogrammetry
KW  - Sinkholes
KW  - Karst
KW  - Discrete Element Method
KW  - Geomechanical Modelling
KW  - Applied Geophysics
KW  - Natural Hazards
KW  - Photogrammetrie
KW  - Erdfälle
KW  - Karst
KW  - Diskrete-Elemente-Methode
KW  - Geomechanische Modellierung
KW  - Angewandte Geophysik
KW  - Naturgefahren
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-432159
ER  - 
TY  - GEN
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Schöpfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Geomechanical modelling of sinkhole development using distinct elements
BT  - model verification for a single void space and application to the Dead Sea area
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Mechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth ∕ diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth ∕ diameter values in each material type may partly reflect sinkhole growth trends.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1061 
KW  - rock mass
KW  - karst
KW  - dissolution
KW  - reflection
KW  - subsidence
KW  - subrosion
KW  - collapse
KW  - simulation
KW  - scale
KW  - fault
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-468435
SN  - 1866-8372
IS  - 1061
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Schöpfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Geomechanical modelling of sinkhole development using distinct elements
BT  - model verification for a single void space and application to the Dead Sea area
JF  - Solid earth
N2  - Mechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth / diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth / diameter values in each material type may partly reflect sinkhole growth trends.
Y1  - 2018
U6  - https://doi.org/10.5194/se-9-1341-2018
SN  - 1869-9510
SN  - 1869-9529
VL  - 9
IS  - 6
SP  - 1341
EP  - 1373
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Watson, Robert A.
A1  - Polom, Ulrich
A1  - Schoepfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Distinct element geomechanical modelling of the formation of sinkhole clusters within large-scale karstic depressions
JF  - Solid earth
N2  - The 2-D distinct element method (DEM) code (PFC2D_V5) is used here to simulate the evolution of subsidence-related karst landforms, such as single and clustered sinkholes, and associated larger-scale depressions. Subsurface material in the DEM model is removed progressively to produce an array of cavities; this simulates a network of subsurface groundwater conduits growing by chemical/mechanical erosion. The growth of the cavity array is coupled mechanically to the gravitationally loaded surroundings, such that cavities can grow also in part by material failure at their margins, which in the limit can produce individual collapse sinkholes. Two end-member growth scenarios of the cavity array and their impact on surface subsidence were examined in the models: (1) cavity growth at the same depth level and growth rate; (2) cavity growth at progressively deepening levels with varying growth rates. These growth scenarios are characterised by differing stress patterns across the cavity array and its overburden, which are in turn an important factor for the formation of sinkholes and uvalalike depressions. For growth scenario (1), a stable compression arch is established around the entire cavity array, hindering sinkhole collapse into individual cavities and favouring block-wise, relatively even subsidence across the whole cavity array. In contrast, for growth scenario (2), the stress system is more heterogeneous, such that local stress concentrations exist around individual cavities, leading to stress interactions and local wall/overburden fractures. Consequently, sinkhole collapses occur in individual cavities, which results in uneven, differential subsidence within a larger-scale depression. Depending on material properties of the cavity-hosting material and the overburden, the larger-scale depression forms either by sinkhole coalescence or by widespread subsidence linked geometrically to the entire cavity array. The results from models with growth scenario (2) are in close agreement with surface morphological and subsurface geophysical observations from an evaporite karst area on the eastern shore of the Dead Sea.
Y1  - 2019
U6  - https://doi.org/10.5194/se-10-1219-2019
SN  - 1869-9510
SN  - 1869-9529
VL  - 10
IS  - 4
SP  - 1219
EP  - 1241
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Mashaikhi, K.
A1  - Oswald, Sascha
A1  - Attinger, Sabine
A1  - Büchel, G.
A1  - Knöller, K.
A1  - Strauch, G.
T1  - Evaluation of groundwater dynamics and quality in the Najd aquifers located in the Sultanate of Oman
JF  - Environmental earth sciences
N2  - The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, delta H-2 and delta O-18 variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region.
KW  - Environmental isotopes
KW  - Groundwater
KW  - Najd aquifer
KW  - Oman
KW  - Recharge
KW  - Water quality
Y1  - 2012
U6  - https://doi.org/10.1007/s12665-011-1331-2
SN  - 1866-6280
VL  - 66
IS  - 4
SP  - 1195
EP  - 1211
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Alawi, Mashal
A1  - Schneider, Beate
A1  - Kallmeyer, Jens
T1  - A procedure for separate recovery of extra- and intracellular DNA from a single marine sediment sample
JF  - Journal of microbiological methods
N2  - Extracellular DNA (eDNA) is a ubiquitous biological compound in aquatic sediment and soil. Previous studies suggested that eDNA plays an important role in biogeochemical element cycling, horizontal gene transfer and stabilization of biofilm structures. Previous methods for eDNA extraction were either not suitable for oligotrophic sediments or only allowed quantification but no genetic analyses. Our procedure is based on cell detachment and eDNA liberation from sediment particles by sequential washing with an alkaline sodium phosphate buffer followed by a separation of cells and eDNA. The separated eDNA is then bound onto silica particles and purified, whereas the intracellular DNA from the separated cells is extracted using a commercial kit. The method provides extra- and intracellular DNA of high purity that is suitable for downstream applications like PCR. Extracellular DNA was extracted from organic-rich shallow sediment of the Baltic Sea, glacially influenced sediment of the Barents Sea and from the oligotrophic South Pacific Gyre. The eDNA concentration in these samples varied from 23 to 626 ng g(-1) wet weight sediment. A number of experiments were performed to verify each processing step. Although extraction efficiency is higher than other published methods, it is not fully quantitative. (C) 2014 Elsevier B.V. All rights reserved.
KW  - Extracellular DNA
KW  - eDNA
KW  - Intracellular DNA
KW  - South Pacific Gyre
KW  - Ancient DNA
KW  - Fossil DNA
Y1  - 2014
U6  - https://doi.org/10.1016/j.mimet.2014.06.009
SN  - 0167-7012
SN  - 1872-8359
VL  - 104
SP  - 36
EP  - 42
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Albrecht, Tanja
A1  - Martin, M.
A1  - Haseloff, M.
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Parameterization for subgrid-scale motion of ice-shelf calving fronts
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - 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.
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-35-2011
SN  - 1994-0416
VL  - 5
IS  - 1
SP  - 35
EP  - 44
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - Part 1: boundary conditions and climatic forcing
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. <br /> We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a "cookbook" for the growing community of PISM users and paleo-ice sheet modelers in general. <br /> For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-599-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 599
EP  - 632
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrich, Sergi
A1  - Frijia, Gianluca
A1  - Parente, Mariano
A1  - Caus, Esmeralda
T1  - The evolution of the earliest representatives of the genus Orbitoides: Implications for Upper Cretaceous biostratigraphy
JF  - Cretaceous research
N2  - The biostratigraphy of Campanian-Maastrichtian carbonate platforms is largely based on the larger foraminiferal genus Orbitoides. However, while the taxonomy and the chronostratigraphic age of the younger species of this genus are well established, there are still many controversies on the earliest species. We have restudied their morphological characters using a large collection of samples from the type-localities and from continuous sections in the southern Pyrenees. Based on these new observations, the long forgotten species O. sanctae-pelagiae is reinstated, while O. dordoniensis is considered a junior synonym. Successive populations of O. hottingeri, O. sanctae-pelagiae and O. douvillei show gradual morphological changes in time marked by an increase in the size and complexity of the macrospheric embryonal apparatus, an increase of the size of the adult specimens of both generations and the progressive appearance and development of true lateral chamberlets. The Font de les Bagasses Unit in the southern Pyrenees preserves a high-resolution archive of the evolution of the earliest Orbitoides. Strontium isotope stratigraphy indicates that the oldest species, O. hottingeri, made its first appearance in the earliest Campanian, close to the Santonian-Campanian boundary, and was replaced by O. sanctae-pelagiae at a level closely corresponding to the boundary between the Placenticeras bidorsatum and Menabites delawarensis ammonite zones. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Larger foraminifera
KW  - Biostratigraphy
KW  - Strontium isotope stratigraphy
KW  - Late cretaceous
KW  - Orbitoides
Y1  - 2014
U6  - https://doi.org/10.1016/j.cretres.2014.04.013
SN  - 0195-6671
SN  - 1095-998X
VL  - 51
SP  - 22
EP  - 34
PB  - Elsevier
CY  - London
ER  - 
TY  - JOUR
A1  - Ali, Saleem H.
A1  - Giurco, Damien
A1  - Arndt, Nicholas
A1  - Nickless, Edmund
A1  - Brown, Graham
A1  - Demetriades, Alecos
A1  - Durrheim, Ray
A1  - Enriquez, Maria Amelia
A1  - Kinnaird, Judith
A1  - Littleboy, Anna
A1  - Meinert, Lawrence D.
A1  - Oberhänsli, Roland
A1  - Salem, Janet
A1  - Schodde, Richard
A1  - Schneider, Gabi
A1  - Vidal, Olivier
A1  - Yakovleva, Natalia
T1  - Mineral supply for sustainable development requires resource governance
JF  - Nature : the international weekly journal of science
N2  - Successful delivery of the United Nations sustainable development goals and implementation of the Paris Agreement requires technologies that utilize a wide range of minerals in vast quantities. Metal recycling and technological change will contribute to sustaining supply, but mining must continue and grow for the foreseeable future to ensure that such minerals remain available to industry. New links are needed between existing institutional frameworks to oversee responsible sourcing of minerals, trajectories for mineral exploration, environmental practices, and consumer awareness of the effects of consumption. Here we present, through analysis of a comprehensive set of data and demand forecasts, an interdisciplinary perspective on how best to ensure ecologically viable continuity of global mineral supply over the coming decades.
Y1  - 2017
U6  - https://doi.org/10.1038/nature21359
SN  - 0028-0836
SN  - 1476-4687
VL  - 543
SP  - 367
EP  - 372
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Alinaghi, Alireza
A1  - Kruger, Frank
T1  - Seismic array analysis and redetermination of depths of earthquakes in Tien-Shan: implications for strength of the crust and lithosphere
JF  - Geophysical journal international
N2  - We have redetermined focal depths of moderate and major earthquakes with reported lower-crust and upper-mantle depths that have occurred in Tien-Shan, since the availability of broad-band array data. Records of earthquakes at global arrays have been used for identification and modelling of depth phases in order to make accurate estimation of focal depths. Our results show that half of the purportedly deep earthquakes are indeed originating from depths attributable to middle-crust and lower-crust regions. Also one exceptional event in the northern foreland of Tien-Shan in Junggar Basin is located in the upper mantle at the depth of 64 km. Such unusually deep earthquakes for intraplate continental tectonic domain are all located at the margin of Tien-Shan with its adjacent stable blocks and at least some of them have occurred where the brittle behaviour of continental rocks is not highly expected. The reverse mechanisms of all these earthquakes and their proximity to formerly subducting and later colliding and underplating stable blocks and their interactions with overlying Tien-Shan are clues to explain this extremity.
KW  - Earthquake source observations
KW  - Seismicity and tectonics
KW  - Body waves
Y1  - 2014
U6  - https://doi.org/10.1093/gji/ggu141
SN  - 0956-540X
SN  - 1365-246X
VL  - 198
IS  - 2
SP  - 1111
EP  - 1129
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - THES
A1  - Allroggen, Niklas
T1  - Observation of subsurface flow from the surface : applications of ground-penetrating radar
BT  - non-invasive time-lapse observation of subsurface flow by using ground-penetrating radar
Y1  - 2015
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Beiter, Daniel
A1  - Tronicke, Jens
T1  - Ground-penetrating radar monitoring of fast subsurface processes
JF  - Geophysics
N2  - Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0737.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - A19
EP  - A23
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Heincke, Bjorn H.
A1  - Koyan, Philipp
A1  - Wheeler, Walter
A1  - Ronning, Jan S.
T1  - 3D ground-penetrating radar attribute classification
BT  - a case study from a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard
JF  - Geophysics
N2  - Ground-penetrating radar (GPR) is a method that can provide detailed information about the near subsurface in sedimentary and carbonate environments. 
The classical interpretation of GPR data (e.g., based on manual feature selection) often is labor-intensive and limited by the experience of the intercally used for seismic interpretation, can provide faster, more repeatable, and less biased interpretations. We have recorded a 3D GPD data set collected across a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard. After performing advanced processing, we compare the results of a classical GPR interpretation to the results of an attribute-based classification. 

Our attribute classification incorporates a selection of dip and textural attributes as the input for a k-means clustering approach. Similar to the results of the classical interpretation, the resulting classes differentiate between undisturbed strata and breccias or fault zones. 
The classes also reveal details inside the breccia pipe that are not discerned in the classical fer that the intrapipe GPR facies result from subtle differences, such as breccia lithology, clast size, or pore-space filling.
Y1  - 2022
U6  - https://doi.org/10.1190/GEO2021-0651.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 87
IS  - 4
SP  - WB19
EP  - WB30
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas Robin
A1  - Booth, Adam D.
A1  - Baker, Sandra E.
A1  - Ellwood, Stephen A.
A1  - Tronicke, Jens
T1  - High-resolution imaging and monitoring of animal tunnels using 3D ground-penetrating radar
JF  - Near surface geophysics
N2  - Ground-penetrating radar is widely used to provide highly resolved images of subsurface sedimentary structures, with implications for processes active in the vadose zone. Frequently overlooked among these structures are tunnels excavated by fossorial animals (e.g., moles). We present two repeated ground-penetrating radar surveys performed a year apart in 2016 and 2017. Careful three-dimensional data processing reveals, in each data set, a pattern of elongated structures that are interpreted as a subsurface mole tunnel network. Our data demonstrate the ability of three-dimensional ground-penetrating radar imaging to non-invasively delineate the small animal tunnels (similar to 5 cm diameter) at a higher spatial and geolocation resolution than has previously been achieved. In turn, this makes repeated surveys and, therefore, long-term monitoring possible. Our results offer valuable insight into the understanding of the near-surface and showcase a potential new application for a geophysical method as well as a non-invasive method of ecological surveying.
KW  - Ground-penetrating radar
KW  - Shallow subsurface
KW  - Environmental
Y1  - 2019
U6  - https://doi.org/10.1002/nsg.12039
SN  - 1569-4445
SN  - 1873-0604
VL  - 17
IS  - 3
SP  - 291
EP  - 298
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Tronicke, Jens
T1  - Attribute-based analysis of time-lapse ground-penetrating radar data
JF  - Geophysics
N2  - Analysis of time-lapse ground-penetrating radar (GPR) data can provide information regarding subsurface hydrological processes, such as preferential flow. However, the analysis of time-lapse data is often limited by data quality; for example, for noisy input data, the interpretation of difference images is often difficult. Motivated by modern image-processing tools, we have developed two robust GPR attributes, which allow us to distinguish amplitude (contrast similarity) and time-shift (structural similarity) variations related to differences between individual time-lapse GPR data sets. We tested and evaluated our attributes using synthetic data of different complexity. Afterward, we applied them to a field data example, in which subsurface flow was induced by an artificial rainfall event. For all examples, we identified our structural similarity attribute to be a robust measure for highlighting time-lapse changes also in data with low signal-to-noise ratios. We determined that our new attribute-based workflow is a promising tool to analyze time-lapse GPR data, especially for imaging subsurface hydrological processes.
Y1  - 2016
U6  - https://doi.org/10.1190/GEO2015-0171.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 81
SP  - H1
EP  - H8
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Tronicke, Jens
A1  - Delock, Marcel
A1  - Böniger, Urs
T1  - Topographic migration of 2D and 3D ground-penetrating radar data considering variable velocities
JF  - Near surface geophysics
N2  - We present a 2D/3D topographic migration scheme for ground-penetrating radar (GPR) data which is able to account for variable velocities by using the root mean square (rms) velocity approximation. We test our migration scheme using a synthetic 2D example and compare our migrated image to the results obtained using common GPR migration approaches. Furthermore, we apply it to 2D and 3D field data. These examples are recorded across common subsurface settings including surface topography and variations in the GPR subsurface velocity field caused by a shallow ground water table. In such field settings, our migration strategy provides well focused images of commonoffset GPR data without the need for a detailed interval velocity model. The synthetic and field examples demonstrate that our topographic migration scheme allows for accurate GPR imaging in the presence of variations in surface topography and subsurface velocity.
Y1  - 2015
U6  - https://doi.org/10.3997/1873-0604.2014037
SN  - 1569-4445
SN  - 1873-0604
VL  - 13
IS  - 3
PB  - European Association of Geoscientists & Engineers
CY  - Houten
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - van Schaik, N. Loes M. B.
A1  - Tronicke, Jens
T1  - 4D ground-penetrating radar during a plot scale dye tracer experiment
JF  - Journal of applied geophysics
N2  - Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Ground penetrating radar
KW  - Time-lapse imaging
KW  - Brilliant blue
Y1  - 2015
U6  - https://doi.org/10.1016/j.jappgeo.2015.04.016
SN  - 0926-9851
SN  - 1879-1859
VL  - 118
SP  - 139
EP  - 144
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Alonso, Ricardo N.
A1  - Bookhagen, Bodo
A1  - Carrapa, Barbara
A1  - Coutand, Isabelle
A1  - Haschke, Michael
A1  - Hilley, George E.
A1  - Schoenbohm, Lindsay M.
A1  - Sobel, Edward
A1  - Strecker, Manfred
A1  - Trauth, Martin H.
A1  - Villanueva, Arturo
T1  - Tectonics, climate and landscape evolution of the Southern Central Andes : the Argentine Puna Plateau and adjacent regions between 22 and 30°S
Y1  - 2006
SN  - 978-3-540- 24329-8
ER  - 
TY  - JOUR
A1  - Alonzo, Michael
A1  - Bookhagen, Bodo
A1  - McFadden, Joseph P.
A1  - Sun, Alex
A1  - Roberts, Dar A.
T1  - Mapping urban forest leaf area index with airborne lidar using penetration metrics and allometry
JF  - Remote sensing of environment : an interdisciplinary journal
N2  - In urban areas, leaf area index (LAI) is a key ecosystem structural attribute with implications for energy and water balance, gas exchange, and anthropogenic energy use. In this study, we estimated LAI spatially using airborne lidar in downtown Santa Barbara, California, USA. We implemented two different modeling approaches. First, we directly estimated effective LAI (LAIe) using scan angle- and clump-corrected lidar laser penetration metrics (LPM). Second, we adapted existing allometric equations to estimate crown structural metrics including tree height and crown base height using lidar. The latter approach allowed for LAI estimates at the individual tree-crown scale. The LPM method, at both high and decimated point densities, resulted in good linear agreement with estimates from ground-based hemispherical photography (r(2) = 0.82, y = 0.99x) using a model that assumed a spherical leaf angle distribution. Within individual tree crown segments, the lidar estimates of crown structure closely paralleled field measurements (e.g., r(2) = 0.87 for crown length). LAI estimates based on the lidar crown measurements corresponded well with estimates from field measurements (r(2) = 0.84, y = 0.97x + 0.10). Consistency of the LPM and allometric lidar methods was also strong at 71 validation plots (r(2) = 0.88) and at 450 additional sample locations across the entire study area (r(2) = 0.72). This level of correspondence exceeded that of the canopy hemispherical photography and allometric, ground-based estimates (r(2) = 0.53). The first-order alignment of these two disparate methods may indicate that the error bounds for mapping LAI in cities are small enough to pursue large scale, spatially explicit estimation. (C) 2015 Elsevier Inc All rights reserved.
KW  - Airborne lidar
KW  - Leaf area index
KW  - Urban ecosystem analysis
KW  - Hemispherical photography
KW  - Allometry
KW  - Vegetation structure
Y1  - 2015
U6  - https://doi.org/10.1016/j.rse.2015.02.025
SN  - 0034-4257
SN  - 1879-0704
VL  - 162
SP  - 141
EP  - 153
PB  - Elsevier
CY  - New York
ER  - 
TY  - GEN
A1  - Alsemgeest, Jitse
A1  - Schröder, S.
A1  - Boettger, Ute
A1  - Pavlov, S. G.
A1  - Weber, I.
A1  - Greshake, A.
A1  - Knöfler, H. -R.
A1  - Altenberger, Uwe
A1  - Hübers, H. -W.
T1  - COMBINED RAMAN-LIBS STUDIES ON IRON SULFIDES TO INVESTIGATE THE EFECTS OF THE LIBS PLASMA ON THE MINERAL COMPOSITION.
T2  - Monthly notices of the Royal Astronomical Society
Y1  - 2016
SN  - 1086-9379
SN  - 1945-5100
VL  - 51
SP  - A147
EP  - A147
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Altenbach, Alexander V.
A1  - Pflaum, U.
A1  - Scheibel, Thomas R.
A1  - Thies, A.
A1  - Timm, M.
A1  - Trauth, Martin H.
T1  - Scaling percentages of benthic forminifera with flux rates of organic carbon
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Strain localization mechanisms in deep seated layered rocks
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Material transport in channelized fluids-examples from hightemperature shear zones and its comparsion with minor deformed ares of the Mid-European Variscan belt
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Fluid enhanced element redistribution, mass transport and volume changes in eclogite and amphibolite facies shear zones of different geological settings
Y1  - 1996
ER  - 
TY  - GEN
A1  - Altenberger, Uwe
T1  - Stress-induced natural transformation of ortho- to clinohypersthene in metagabbros of the Ivrea Zone, Northern Italy
N2  - Orthopyroxenes of a high temperature protomylonite of the Ivrea Zone, Northern Italy show twin like polysynthetic lamellae parallel to {210} of the hypersthene host. The transformation is caused by plastic deformation under high metamorphic conditions which has resulted in dynamic recrystallization of pyroxene and plagioclase. The lamellae consist of clinohypersthene. The twin plane and the lamellar clino-orthoinversion of hypersthene due to natural deformation have not been described hitherto.
N2  - Orthopyroxene aus hoch temperierten Protomyloniten der Ivrea-Zone, Nord Italien zeigen polysynthetische Lamellen parallel {210} des Wirtes. Ihr Erscheinungsbild entspricht Deformationszwillingen. Die Lamellen sind invertiert zu Klinohypersthen. Die Ortho-Klino-Transformation ist auf eine Hochtemperaturdeformation zurückzuführen, wie dies anhand der dynamischen Rekristallisation der Pyroxene und Plagioklase bewiesen werden kann. Weder die speziellen Verwachsungsflächen noch die Ortho-Klino-Inversion durch natürliche Deformation wurden bisher beschrieben.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 099 
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-40778
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Cisterna, Clara
A1  - Günter, Christina
A1  - Gutiérrez, Adolfo Antonio
A1  - Rosales, J.
T1  - Tectono-metamorphic evolution of the proto-Andean margin of Gondwana
BT  - Evidence of internal high-grade metamorphism along the northern portion of the Famatinian orogen, Sierra de Aconquija, Sierras Pampeanas Orientales, Argentina
JF  - Journal of South American earth sciences
N2  - The present work gives a detailed analysis of the metamorphic and structural evolution of the back-arc portion of the Famatinian Orogen exposed in the southern Sierra de Aconquija (Cuesta de La Chilca segment) in the Sierras Pampeanas Orientales (Eastern Pampean Sierras). The Pampeanas Orientales include from north to south the Aconquija, Ambato and Ancasti mountains. They are mainly composed of middle to high grade metasedimentary units and magmatic rocks. 
At the south end of the Sierra de Aconquija, along an east to west segment extending over nearly 10 km (Cuesta de La Chilca), large volumes of metasedimentary rocks crop out. The eastern metasediments were defined as members of the El Portezuelo Metamorphic-Igneous Complex (EPMIC) or Eastern block and the western ones relate to the Quebrada del Molle Metamorphic Complex (QMMC) or Western block. The two blocks are divided by the La Chilca Shear Zone, which is reactivated as the Rio Chanarito fault. 
The EPMIC, forming the hanging wall, is composed of schists, gneisses and rare amphibolites, calc- silicate schists, marbles and migmatites. The rocks underwent multiple episodes of deformation and a late high strain-rate episode with gradually increasing mylonitization to the west. Metamorphism progrades from a M-1 phase to the peak M-3, characterized by the reactions: Qtz + Pl + Bt +/- Ms -> Grt + Bt(2) + Pl(2) +/- Sil +/- Kfs, Qtz + Bt + Sil -> Crd + Kfs and Qtz + Grt + Sil -> Crd. The M-3 assemblage is coeval with the dominant foliation related to a third deformational phase (D-3). 

The QMMC, forming the foot wall, is made up of fine-grained banded quartz - biotite schists with quartz veins and quartz-feldspar-rich pegmatites. To the east, schists are also overprinted by mylonitization. The M-3 peak assemblage is quartz + biotite + plagioclase +/- garnet +/- sillimanite +/- muscovite +/- ilmenite +/- magnetite +/- apatite. 

The studied segment suffered multiphase deformation and metamorphism. Some of these phases can be correlated between both blocks. D-1 is locally preserved in scarce outcrops in the EPMIC but is the dominant in the QMMC, where S-1 is nearly parallel to S-0. In the EPMIC, D-2 is represented by the S-2 foliation, related to the F-2 folding that overprints S-1, with dominant strike NNW - SSE and high angles dip to the E. D-3 in the EPMIC have F-3 folds with axis oblique to S-2; the S-3 foliation has striking NW - SE dipping steeply to the E or W and develops interference patterns. In the QMMC, S-2 (D-2) is a discontinuous cleavage oblique to S-1 and transposed by S-3 (D-3), subparallel to S-1. Such structures in the QMMC developed at subsolidus conditions and could be correlated to those of the EPMIC, which formed under higher P-T conditions. The penetrative deformation D-2 in the EPMIC occurred during a prograde path with syntectonic growth of garnet reaching P-T conditions of 640 degrees C and 0.54 GPa in the EPMIC. This stage was followed by a penetrative deformation D-3 with syn-kinematic growth of garnet, cordierite and plagioclase. Peak P-T conditions calculated for M-3 are 710 degrees C and 0.60 GPa, preserved in the western part of the EPMIC, west of the unnamed fault.
The schists from the QMMC suffered the early low grade M-1 metamorphism with minimum PT conditions of ca 400 degrees C and 0.35 GPa, comparable to the fine schists (M-1) outcropping to the east. The D-2 deformation is associated with the prograde M-2 metamorphism. The penetrative D-3 stage is related to a medium grade metamorphism M-3, with peak conditions at ca 590 degrees C and 0.55 GPa.
The superimposed stages of deformation and metamorphism reaching high P-T conditions followed by isothermal decompression, defining a clockwise orogenic P-T path. During the Lower Paleozoic, folds were superimposed and recrystallization as well as partial melting at peak conditions occurred. Similar characteristics were described from the basement from other Famatinian-dominated locations of the Sierra de Aconquija and other ranges of the Sierras Pampeanas Orientales.
KW  - Famatinian
KW  - Sierras Pampeanas Orientales
KW  - Cuesta de la chilca
KW  - PT path
Y1  - 2021
U6  - https://doi.org/10.1016/j.jsames.2021.103305
SN  - 0895-9811
VL  - 110
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Kruhl, J. H.
T1  - The long life of a thin and dry-temperature shear zone in the Hercynian lower crust of Calabria (s.Italy)
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Mejia Jimenez, D. M.
A1  - Günter, C.
A1  - Sierra Rodriguez, G. I.
A1  - Scheffler, F.
A1  - Oberhänsli, Roland
T1  - The Garzn Massif, Colombia-a new ultrahigh-temperature metamorphic complex in the early Neoproterozoic of northern South America
JF  - Mineralogy and petrology
N2  - The Garzn Complex of the Garzn Massif in SW Colombia is composed of the Vergel Granulite Unit (VG) and the Las Margaritas Migmatite Unit (LMM). Previous studies reveal peak temperature conditions for the VG of about 740 A degrees C. The present study considers the remarkable exsolution phenomena in feldspars and pyroxenes and titanium-in-quartz thermometry. Recalculated ternary feldspar compositions indicate temperatures around 900-1,000 A degrees C just at or above the ultra-high temperature-metamorphism (UHTM) boundary of granulites. The calculated temperatures range of exsolved ortho- and clinopyroxenes also supports the existence of an UHTM event. In addition, titanium-in-quartz thermometry points towards ultra-high temperatures. It is the first known UHTM crustal segment in the northern part of South America. Although a mean geothermal gradient of ca 38 A degrees C km(-1) could imply additional heat supply in the lower crust controlling this extreme of peak metamorphism, an alternative model is suggested. The formation of the Vergel Granulite Unit is supposed to be formed in a continental back-arc environment with a thinned and weakened crust behind a magmatic arc (Guapotn-Mancagua Gneiss) followed by collision. In contrast, rocks of the adjacent Las Margaritas Migmatite Unit display "normal" granulite facies temperatures and are formed in a colder lower crust outside the arc, preserved by the Guapotn-Mancagu Gneiss. Back-arc formation was followed by inversion and thickening of the basin. The three units that form the modern-day Garzn Massif, were juxtaposed upon each other during collision (at ca. 1,000 Ma) and exhumation. The collision leading to the deformation of the studied area is part of the Grenville orogeny leading to the amalgamation of Rodinia.
Y1  - 2012
U6  - https://doi.org/10.1007/s00710-012-0202-1
SN  - 0930-0708
VL  - 105
IS  - 3-4
SP  - 171
EP  - 185
PB  - Springer
CY  - Wien
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Oberhänsli, Roland
A1  - Stein, Eckehard
A1  - Moghni, Mohsen
T1  - Geochemistry, tectonic setting and geodynamic position of late orogenic dikes in the Melibocus Massiv, Bergstraesser Odenwald
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Prosser, Giacomo
A1  - Grande, Atonella
A1  - Günter, Christina
A1  - Langone, Antonio
T1  - A seismogenic zone in the deep crust indicated by pseudotachylytes and ultramylonites in granulite-facies rocks of Calabria (Southern Italy)
JF  - Contributions to mineralogy and petrology
N2  - Pseudotachylyte veins frequently associated with mylonites and ultramylonites occur within migmatitic paragneisses, metamonzodiorites, as well as felsic and mafic granulites at the base of the section of the Hercynian lower crust exposed in Calabria (Southern Italy). The crustal section is tectonically superposed on lower grade units. Ultramylonites and pseudotachylytes are particularly well developed in migmatitic paragneisses, whereas sparse fault-related pseudotachylytes and thin mylonite/ultramylonite bands occur in granulite-facies rocks. The presence of sillimanite and clinopyroxene in ultramylonites and mylonites indicates that relatively high-temperature conditions preceded the formation of pseudotachylytes. We have analysed pseudotachylytes from different rock types to ascertain their deep crustal origin and to better understand the relationships between brittle and ductile processes during deformation of the deeper crust. Different protoliths were selected to test how lithology controls pseudotachylyte composition and textures. In migmatites and felsic granulites, euhedral or cauliflower-shaped garnets directly crystallized from pseudotachylyte melts of near andesitic composition. This indicates that pseudotachylytes originated at deep crustal conditions (> 0.75 GPa). In mafic protoliths, quenched needle-to-feather-shaped high-alumina orthopyroxene occurs in contact with newly crystallized plagioclase. The pyroxene crystallizes in garnet-free and garnet-bearing veins. The simultaneous growth of orthopyroxene and plagioclase as well as almandine, suggests lower crustal origin, with pressures in excess of 0.85 GPa. The existence of melts of different composition in the same vein indicates the stepwise, non-equilibrium conditions of frictional melting. Melt formed and intruded into pre-existing anisotropies. In mafic granulites, brittle faulting is localized in a previously formed thin high-temperature mylonite bands. migmatitic gneisses are deformed into ultramylonite domains characterized by s-c fabric. Small grain size and fluids lowered the effective stress on the c planes favouring a seismic event and the consequent melt generation. Microstructures and ductile deformation of pseudotachylytes suggest continuous ductile flow punctuated by episodes of high-strain rate, leading to seismic events and melting.
KW  - Pseudotachylyte
KW  - Calabria
KW  - Lower crust
KW  - Palaeo-seismicity
Y1  - 2013
U6  - https://doi.org/10.1007/s00410-013-0904-3
SN  - 0010-7999
VL  - 166
IS  - 4
SP  - 975
EP  - 994
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
A1  - Wilhelm, Stefan
T1  - Ductile deformation of K-feldspar in eclogite facies shear zones in the Bergen Arcs, Norway : tectonophysics
Y1  - 2000
ER  - 
TY  - THES
A1  - Ambili, Anoop
T1  - Lake sediments as climate and tectonic archives in the Indian summer monsoon domain
T1  - Seesedimente als Klima- und Tektonikarchive im Einflussbereich des Indischen Sommermonsuns
N2  - The Indian summer monsoon (ISM) is one of the largest climate systems on earth and impacts the livelihood of nearly 40% of the world’s population. Despite dedicated efforts, a comprehensive picture of monsoon variability has proved elusive largely due to the absence of long term high resolution records, spatial inhomogeneity of the monsoon precipitation, and the complex forcing mechanisms (solar insolation, internal teleconnections for e.g., El Niño-Southern Oscillation, tropical-midlatitude interactions). My work aims to improve the understanding of monsoon variability through generation of long term high resolution palaeoclimate data from climatically sensitive regions in the ISM and westerlies domain. To achieve this aim I have (i) identified proxies (sedimentological, geochemical, isotopic, and mineralogical) that are sensitive to environmental changes; (ii) used the identified proxies to generate long term palaeoclimate data from two climatically sensitive regions, one in NW Himalayas (transitional westerlies and ISM domain in the Spiti valley and one in the core monsoon zone (Lonar lake) in central India); (iii) undertaken a regional overview to generate “snapshots” of selected time slices; and (iv) interpreted the spatial precipitation anomalies in terms of those caused by modern teleconnections. This approach must be considered only as the first step towards identifying the past teleconnections as the boundary conditions in the past were significantly different from today and would have impacted the precipitation anomalies. As the Spiti valley is located in the in the active tectonic orogen of Himalayas, it was essential to understand the role of regional tectonics to make valid interpretations of catchment erosion and detrital influx into the lake. My approach of using integrated structural/morphometric and geomorphic signatures provided clear evidence for active tectonics in this area and demonstrated the suitability of these lacustrine sediments as palaleoseismic archives. The investigations on the lacustrine outcrops in Spiti valley also provided information on changes in seasonality of precipitation and occurrence of frequent and intense periods (ca. 6.8-6.1 cal ka BP) of detrital influx indicating extreme hydrological events in the past. Regional comparison for this time slice indicates a possible extended “break-monsoon like” mode for the monsoon that favors enhanced precipitation over the Tibetan plateau, Himalayas and their foothills. My studies on surface sediments from Lonar lake helped to identify environmentally sensitive proxies which could also be used to interpret palaeodata obtained from a ca. 10m long core raised from the lake in 2008. The core encompasses the entire Holocene and is the first well dated (by 14C) archive from the core monsoon zone of central India. My identification of authigenic evaporite gaylussite crystals within the core sediments provided evidence of exceptionally drier conditions during 4.7-3.9 and 2.0-0.5 cal ka BP. Additionally, isotopic investigations on these crystals provided information on eutrophication, stratification, and carbon cycling processes in the lake.
N2  - Der Indische Sommer Monsun (ISM) ist eines der bedeutendsten Klimaphänomene auf der Erde und hat großen Einfluss auf die Lebensbedingungen und -grundlagen von nahezu 40% der Weltbevölkerung. Trotz großer Bemühungen ist es bisher nicht gelungen ein genaues und umfassendes Verständnis der Monsun-Variabilität zu gewinnen. Hauptgründe dafür sind das Fehlen von langjährigen und hochaufgelösten Klimazeitreihen, räumlichen Inhomogenitäten in den Niederschlagsverteilungen und die Komplexität der treibenden klimatischen Mechanismen (Sonneneinstrahlung, interne Wechselwirkungen des Klimasystems, wie z.B. zwischen Tropen und mittleren Breiten oder die Auswirkungen der El Niño Oszillation). Die Zielsetzung der hier vorgestellten Arbeit ist ein verbessertes Verständnis der Monsun-Variabilität zu entwickeln, auf Basis von hochaufgelösten und weit reichenden Paläoklimazeitreihen aus klimasensitiven Regionen des ISM und der Westwindzone. Um die Zielsetzung umzusetzen habe ich: (i) Proxys identifiziert (sedimentologische, geochemische, isotopische, und mineralogische), die empfindlich auf Umweltveränderungen reagieren; (ii) die identifizierten Proxys zur Erzeugung von langjährigen Paläoklima-Daten für zwei klimasensible Regionen verwendet, eine im NW des Himalaja (Übergangs-Westwindzone und ISM Gebiet von Spity Valley) und eine in der Kernzone des Monsun (Lonar-See) in Zentralindien; (iii) Übersichts-"Momentaufnahmen" der regionalen klimatischen Bedingungen für ausgewählte Zeitpunkte der Vergangenheit erzeugt; und (iv) räumliche Niederschlagsanomalien in Hinblick auf heutige Wechselbeziehungen im Klimasystem interpretiert. Dieser Ansatz stellt allerdings nur einen ersten Schritt zur Identifizierung von paläoklimatischen Wechselbeziehungen im Monsunsystem dar, da sich die Randbedingungen in der Vergangenheit deutlich von den heutigen unterscheiden und diese einen signifikanten Einfluss auf die Niederschlagsanomalien haben. Da das Spity Valley im tektonisch aktiven Himalaja-Orogen lokalisiert ist, ist es von entscheidender Bedeutung die regionalen tektonischen Prozesse zu verstehen, um Erosionsvorgänge des Einzugsgebiets und die Einfuhr von Detritus in den See korrekt interpretieren zu können. Mein Ansatz der Nutzung kombinierter strukturell/morphometrischer und geomorphologischer Charakteristiken lieferte klare Beweise für aktive Tektonik im untersuchten Gebiet und demonstrierte damit die Eignung dieser lakustrinen Sedimente als paläoseismisches Archiv. Die Untersuchung lakustriner Aufschlüsse in Spity Valley lieferte auch Informationen saisonale Änderung der Niederschlagsverteilung sowie das Auftreten von häufigen und intensiven Perioden (ca. 6,8-6,1 cal ka BP) detritischer Einfuhr, welche auf extreme hydrologische Ereignisse in der Vergangenheit schließen lässt. Ein regionaler Vergleich dieser Periode deutet auf einen möglicherweise erweiterten „break-monsoon-like“ Modus für den Monsun hin, welcher hohe Niederschläge über dem Tibetischen Plateau, dem Himalaja und seinen Gebirgsausläufern begünstigt. Meine Studien an den Oberflächensedimenten des Lonar-Sees haben dazu beigetragen umweltsensitive Proxys zu identifizieren, die auch zur Interpretation von Paläodaten von einem ca. 10 m langen Sedimentkern genutzt wurden, der 2008 erbohrt wurde. Der Kern umfasst das gesamte Holozän und stellt das erste gut 14C-datierte Archiv aus der Kernmonsunzone Zentralindiens dar. Die Identifizierung von authigenen Evaporit-Kristallen (Gaylussite) innerhalb der Sedimente liefert einen Beweis für ungewöhnlich trockene Bedingungen in den Perioden zwischen 4,7-3,9 und 2,0-0,5 cal ka BP. Darüber hinaus lieferten Isotopen-Untersuchungen dieser Kristalle Informationen zur Eutrophierung, Stratifikation und zum Kohlenstoff-Kreislauf des Sees.
KW  - Gaylussite
KW  - Indische Sommer Monsun
KW  - Seesediment
KW  - Spity Valley
KW  - Lonarsee
KW  - Gaylussite
KW  - Indian summer monsoon
KW  - Lake sediments
KW  - Spiti valley
KW  - Lonar lake
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64799
ER  - 
TY  - JOUR
A1  - Aminov, Jovid
A1  - Ding, Lin
A1  - Mamadjonov, Yunus
A1  - Dupont-Nivet, Guillaume
A1  - Aminov, Jamshed
A1  - Zhang, Li-Yun
A1  - Yoqubov, Shokirjon
A1  - Aminov, Javhar
A1  - Abdulov, Sherzod
T1  - Pamir Plateau formation and crustal thickening before the India-Asia collision inferred from dating and petrology of the 110-92 Ma Southern Pamir volcanic sequence
JF  - Gondwana research : international geoscience journal ; official journal of the International Association for Gondwana Research
N2  - The formation of the Pamir is a key component of the India-Asia collision with major implications for lithospheric processes, plateau formation, land-sea configurations and associated climate changes. Although the formation of the Pamir is traditionally linked to Cenozoic processes associated with the India-Asia collision, the contribution of the Mesozoic tectonic evolution remains poorly understood. The Pamir was formed by the suturing of Gondwanan terranes to the south margin of Eurasia, however, the timing and tectonic mechanisms associated with this Mesozoic accretion remain poorly constrained. These processes are recorded by several igneous belts within these terranes, which are not well studied. Within the Southern Pamir, the Albian-Turonian volcanic rocks and comagmatic plutons of the Kyzylrabat Igneous Complex (KIC) provide an important and still unconstrained record of the Pamir evolution. Here we provide the age, origin and the geodynamic setting of the KIC volcanics by studying their petrology, zircon U-Pb geochronology, geochemistry and isotope composition.17 samples from the KIC volcanics yield U-Pb ages spanning from 92 to 110 Ma. The volcanics are intermediate to acidic in composition (SiO2 = 56-69 wt%) and exhibit high-K calc-alkaline and shoshonitic affinity (K2O/Na2O = 12.2 wt%). They show enrichment in LILE and LREE and depletion in HFSE and HREE with negative Ta, Ti and Nb anomalies, suggesting an arc-related tectonic setting for their formation. Low sNd(t) values (from 9.1 to 4.7), relatively high Sr-87/Sr-86(i) ratios (0.7069-0.7096) and broad range of zircon stif values (from 22.6 to 1.5) suggest a mixture of different magma sources. These features suggest that volcanics were derived by crustal under- or intraplating of an enriched subduction-related mantle shoshonitic magmas, by heating and partial melting of the lower crust, and by mixing of both magma components. Our results further imply that the KIC volcanics represent a shoshonitic suite typical of an evolution from active continental arc to post-collisional setting with a steepening of the Benioff zone and thickening of the crust toward the back-arc. This setting is best explained by the subduction- collision transition along the Shyok suture due to accretion of the Kohistan island arc to the Karakoram. This suggests that a significant part of the crustal shortening and thickening accommodated in the Pamir occurred in the Mesozoic before the India-Asia collision with implications for regional tectonic models. This further suggests the Pamir was already a major topographic feature with potentially important paleoclimate forcing such as the monsoonal circulation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
KW  - Southern Pamir
KW  - Cretaceous
KW  - Volcanic rocks
KW  - Geochemistry
KW  - Geochronology
KW  - Petrogenesis
Y1  - 2017
U6  - https://doi.org/10.1016/j.gr.2017.08.003
SN  - 1342-937X
SN  - 1878-0571
VL  - 51
SP  - 310
EP  - 326
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Amour, Frederic
A1  - Mutti, Maria
A1  - Christ, Nicolas
A1  - Immenhauser, Adrian
A1  - Benson, Gregory S.
A1  - Agar, Susan M.
A1  - Tomas, Sara
A1  - Kabiri, Lahcen
T1  - Outcrop analog for an oolitic carbonate ramp reservoir a scale-dependent geologic modeling approach based on stratigraphic hierarchy
JF  - AAPG bulletin
N2  - Considerable effort has been devoted to the development of simulation algorithms for facies modeling, whereas a discussion of how to combine those techniques has not existed. The integration of multiple geologic data into a three-dimensional model, which requires the combination of simulation techniques, is yet a current challenge for reservoir modeling. This article presents a thought process that guides the acquisition and modeling of geologic data at various scales. Our work is based on outcrop data collected from a Jurassic carbonate ramp located in the High Atlas mountain range of Morocco. The study window is 1 km (0.6 mi) wide and 100 m (328.1 ft) thick. We describe and model the spatial and hierarchical arrangement of carbonate bodies spanning from largest to smallest: (1) stacking pattern of high-frequency depositional sequences, (2) facies association, and (3) lithofacies. Five sequence boundaries were modeled using differential global position system mapping and light detection and ranging data. The surface-based model shows a low-angle profile with modest paleotopographic relief at the inner-to-middle ramp transition. Facies associations were populated using truncated Gaussian simulation to preserve ordered trends between the inner, middle, and outer ramps. At the lithofacies scale, field observations and statistical analysis show a mosaiclike distribution that was simulated using a fully stochastic approach with sequential indicator simulation.
 This study observes that the use of one single simulation technique is unlikely to correctly model the natural patterns and variability of carbonate rocks. The selection and implementation of different techniques customized for each level of the stratigraphic hierarchy will provide the essential computing flexibility to model carbonate settings. This study demonstrates that a scale-dependent modeling approach should be a common procedure when building subsurface and outcrop models.
Y1  - 2013
U6  - https://doi.org/10.1306/10231212039
SN  - 0149-1423
VL  - 97
IS  - 5
SP  - 845
EP  - 871
PB  - American Association of Petroleum Geologists
CY  - Tulsa
ER  - 
TY  - THES
A1  - Amour, Frédéric
T1  - 3-D modeling of shallow-water carbonate systems : a scale-dependent approach based on quantitative outcrop studies
T1  - 3-D Modellierung von Flachwasser-Karbonat-Sytemen : eine skalenabhängige Herangehensweise basierend auf quantitativen Aufschlussstudien
N2  - The study of outcrop modeling is located at the interface between two fields of expertise, Sedimentology and Computing Geoscience, which respectively investigates and simulates geological heterogeneity observed in the sedimentary record. During the last past years, modeling tools and techniques were constantly improved. In parallel, the study of Phanerozoic carbonate deposits emphasized the common occurrence of a random facies distribution along single depositional domain. Although both fields of expertise are intrinsically linked during outcrop simulation, their respective advances have not been combined in literature to enhance carbonate modeling studies. The present study re-examines the modeling strategy adapted to the simulation of shallow-water carbonate systems, based on a close relationship between field sedimentology and modeling capabilities. In the present study, the evaluation of three commonly used algorithms Truncated Gaussian Simulation (TGSim), Sequential Indicator Simulation (SISim), and Indicator Kriging (IK), were performed for the first time using visual and quantitative comparisons on an ideally suited carbonate outcrop. The results show that the heterogeneity of carbonate rocks cannot be fully simulated using one single algorithm. The operating mode of each algorithm involves capabilities as well as drawbacks that are not capable to match all field observations carried out across the modeling area. Two end members in the spectrum of carbonate depositional settings, a low-angle Jurassic ramp (High Atlas, Morocco) and a Triassic isolated platform (Dolomites, Italy), were investigated to obtain a complete overview of the geological heterogeneity in shallow-water carbonate systems. Field sedimentology and statistical analysis performed on the type, morphology, distribution, and association of carbonate bodies and combined with palaeodepositional reconstructions, emphasize similar results. At the basin scale (x 1 km), facies association, composed of facies recording similar depositional conditions, displays linear and ordered transitions between depositional domains. Contrarily, at the bedding scale (x 0.1 km), individual lithofacies type shows a mosaic-like distribution consisting of an arrangement of spatially independent lithofacies bodies along the depositional profile. The increase of spatial disorder from the basin to bedding scale results from the influence of autocyclic factors on the transport and deposition of carbonate sediments. Scale-dependent types of carbonate heterogeneity are linked with the evaluation of algorithms in order to establish a modeling strategy that considers both the sedimentary characteristics of the outcrop and the modeling capabilities. A surface-based modeling approach was used to model depositional sequences. Facies associations were populated using TGSim to preserve ordered trends between depositional domains. At the lithofacies scale, a fully stochastic approach with SISim was applied to simulate a mosaic-like lithofacies distribution. This new workflow is designed to improve the simulation of carbonate rocks, based on the modeling of each scale of heterogeneity individually. Contrarily to simulation methods applied in literature, the present study considers that the use of one single simulation technique is unlikely to correctly model the natural patterns and variability of carbonate rocks. The implementation of different techniques customized for each level of the stratigraphic hierarchy provides the essential computing flexibility to model carbonate systems. Closer feedback between advances carried out in the field of Sedimentology and Computing Geoscience should be promoted during future outcrop simulations for the enhancement of 3-D geological models.
N2  - Das Modellieren von geologischen Aufschlüssen liegt der Schnittstelle zwischen zwei geo-logischen Teildisziplinen, der Sedimentologie und der geologischen Modellierung. Hierbei werden geologische Heterogenitäten untersucht und simuliert, welche im Aufschluss beobachtet wurden. Während der letzten Jahre haben sich die Werkzeuge und die Technik der Modellierung stetig weiter-entwickelt. Parallel dazu hat die Untersuchung der phanerozoischen Karbonatablagerungen ihren Fokus auf gemeinsamen Vorkommen von zufälligen Faziesverteilungen in beiden Ablagerungs-gebieten. Obwohl beide Teildisziplinen durch die Aufschlussmodellierung eigentlich verbunden sind, wurden ihre jeweiligen Vorteile in der Literatur nicht miteinander verbunden, um so eine Verbesserung ähnlicher Studien zu erreichen. Die vorliegende Studie überprüft erneut die Modellierungsstrategie, angepasst an die Simulation von Flachwasser-Karbonat-Systemen und basierend auf einer engen Beziehung zwischen Sedimentologie und Modellierung. Die vorliegende Arbeit behandelt erstmals die Evaluierung der drei am häufigsten verwendeten Algorithmen „Truncated Gaussian Simulation (TGSim)“, „Sequential Indicator Simulation (SISim)“ und „Indicator Kriging (IK)“, um sie visuell und quantitativ mit dem entsprechenden Aufschluss zu vergleichen. Die Ergebnisse zeigen, dass die Heterogenität von Karbonatgesteinen nicht komplett mit nur einem Algorithmus simuliert werden kann. Die Eigenschaften jedes einzelnen Algorithmus beinhalten Vor- und Nachteile, sodass kein Algorithmus alle Beobachtungen aus dem Aufschluss widerspiegelt. Die zwei Endglieder im Spektrum der Ablagerungsbedingungen von Karbonaten, eine flachwinklige, jurassische Karbonat-Rampe (Hoher Atlas, Marokko) und eine isolierte, triassische Plattform (Dolomiten, Italien), wurden untersucht, um einen kompletten Überblick über die verschiedenen Heterogenitäten in Flachwasser-Karbonat- Systemen zu erhalten. Sedimentologische und statistische Analysen wurden für die verschiedenen Typen, Morphologien, Verteilungen und Assoziationen von Karbonatablagerungen durchgeführt und mit paläogeografischen Rekonstruktionen kombiniert und zeigen ähnliche Ergebnisse. Im Beckenmaßstab zeigen die Faziesassoziationen, bestehend aus Fazieszonen mit ähnlichen Ablagerungsbedingungen, einen linearen und kontinuierlichen Übergang zwischen den einzelnen Ablagerungsbereichen. Im Gegensatz dazu zeigt für einzelne Lithofaziestypen im Maßstab einzelner Schichten eine mosaikartige Verteilung, bestehend aus einer Anordnung räumlich unabhängiger Lithofazieszonen entlang des Ablagerungsprofils. Das Ansteigen der räumlichen Unordnung von der beckenweiten Ablagerung zur Ablagerung einzelner Schichten resultiert aus dem Einfluss autozyklischer Faktoren bei der Ablagerung von Karbonaten. Die Skalenabhängigkeit von Karbonat-Heterogenität ist mit der Auswertung der Algorithmen verknüpft um eine Modellierungsstrategie zu etablieren, welche sowohl die sedimentären Charakteristiken des Aufschlusses als auch die Modellierfähigkeit berücksichtigt. Für die Modellierung der Ablagerungssequenzen wurde ein flächenbasierter Ansatz verwendet. Die Faziesassoziationen wurden durch die Benutzung des TGSim-Algorithmus simuliert, um die regulären Trends zwischen den einzelnen Ablagerungsgebieten zu erhalten. Im Bereich der verschiedenen Lithofazien wurde mit dem SISim-Algorithmus, ein voll stochastischer Ansatz angewendet, um die mosaikartige Verteilung der Lithofazies-Typen zu simulieren. Dieser neue Arbeitsablauf wurde konzipiert, um die Simulierung von Karbonaten auf Basis der einzelnen Heterogenitäten in verschiedenen Größenordnungen zu verbessern. Im Gegensatz zu den in der Literatur angewendeten Simulationsmethoden berücksichtigt diese Studie, dass eine einzelne Modellierungstechnik die natürlichen Ablagerungsmuster und Variabilität von Karbonaten wahrscheinlich nicht korrekt abbildet. Die Einführung verschiedener Techniken, angepasst auf die verschiedenen Ebenen der stratigrafischen Hierarchie, liefert die notwendige Flexibilität um Karbonatsysteme korrekt zu modellieren. Eine enge Verknüpfung zwischen den Fortschritten auf dem Gebieten der Sedimentologie und dem Gebiet der modellierenden Geowissenschaften sollte weiterhin bestehen, um auch zukünftig bei der Simulation von geologischen Gelände-Aufschlüssen eine Verbesserung der 3-D-Modellierung zu erreichen.
KW  - Karbonat
KW  - 3-D Modellierung
KW  - Aufschluss-Modellierung
KW  - Quantitative Daten
KW  - Skala
KW  - Stochastischer Algorithmus
KW  - Carbonate
KW  - 3-D outcrop modeling
KW  - quantitative data
KW  - scale
KW  - stochastic algorithms
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-66621
ER  - 
TY  - JOUR
A1  - Andermann, Christoff
A1  - Crave, Alain
A1  - Gloaguen, Richard
A1  - Davy, Philippe
A1  - Bonnet, Stephane
T1  - Connecting source and transport: Suspended sediments in the Nepal Himalayas
JF  - Earth & planetary science letters
N2  - Understanding the dynamics of sediment fluxes is a key issue to constrain modern erosion rates in mountain belts and determine the still debated level of control exerted by precipitation, topography and tectonics. The well defined monsoon seasonality in the Himalayas, together with active tectonics and strong relief provide an ideal environment to assess these possible interactions. For this purpose, we present a new compilation of daily suspended sediment data for 12 stations of the major rivers of the Nepal Himalayas. We analyze the relationships of sediment transport with daily river discharge and precipitation data as well as with morphometric parameters. We show that suspended sediment concentrations vary systematically through the seasons and asynchronously to river discharge displaying a hysteresis effect. This clockwise hysteresis effect disappears when suspended sediment fluxes are directly compared with direct storm discharge. Therefore we attribute the hysteresis effect to groundwater dilution rather than a sediment supply limitation. We infer a rating model to calculate erosion rates directly from long river discharge chronicles. We show that, when normalized by drainage area and mean sediment flux, all rivers exhibit the same trend. This similarity implies that all river basins have the same erosion behavior, independent of location, size and catchment characteristics. Erosion rates calculated from suspended sediment fluxes range between 0.1 and 2.8 mm/yr. The erosion rates of the three main basins of Nepal are in the range 0.9-1.5 mm/yr. Erosion rates in the Higher Himalayas are relatively low ( <0.5 mm/yr, except for Kali Gandaki), while in the Lesser Himalayas they range from 0.2 to 2 mm/yr. We propose that material transport in the rivers depends on hillslope sediment supply, which is, in turn, controlled by those rainfalls producing direct runoff. In other words, the rivers in the Nepal Himalayas are supply-limited and the hillsopes as a contributing source are transport-limited. We also show that erosion processes are not as much controlled by infrequently occurring extreme precipitation events, than by moderate ones with a high recurrence interval.
KW  - suspended sediment transport
KW  - Himalayas
KW  - erosion
KW  - sediment flux hysteresis
KW  - monsoon river hydrology
KW  - Himalayan rivers
Y1  - 2012
U6  - https://doi.org/10.1016/j.epsl.2012.06.059
SN  - 0012-821X
VL  - 351
SP  - 158
EP  - 170
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Andersen, Jane Lund
A1  - Egholm, D. L.
A1  - Knudsen, M. F.
A1  - Jansen, John D.
A1  - Nielsen, S. B.
T1  - The periglacial engine of mountain erosion - Part 1: Rates of frost cracking and frost creep
JF  - Earth surface dynamics
N2  - With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint is easily distinguished by its characteristic fjords and U-shaped valleys, the periglacial fingerprint is more subtle but potentially prevails in some mid- to high-latitude landscapes. Previous models have advocated a frost-driven control on debris production at steep headwalls and glacial valley sides. Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil mantle, which characterises such surfaces. We present a new model that quantifies two key physical processes: frost cracking and frost creep, as a function of both temperature and sediment thickness. Our results yield new insights into how climate and sediment transport properties combine to scale the intensity of periglacial processes. The thickness of the soil mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can provide optimal conditions for only one of those processes at a time. Finally, quantifying these relations also opens up the possibility of including periglacial processes in large-scale, long-term landscape evolution models, as demonstrated in a companion paper.
Y1  - 2015
U6  - https://doi.org/10.5194/esurf-3-447-2015
SN  - 2196-6311
SN  - 2196-632X
VL  - 3
IS  - 4
SP  - 447
EP  - 462
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - THES
A1  - Angelopoulos, Michael
T1  - Mechanisms of sub-aquatic permafrost evolution in Arctic coastal environments
BT  - field observations and modelling of submerged ice-rich permafrost deposits and thermokarst lagoons in northeastern Siberia
N2  - Subsea permafrost is perennially cryotic earth material that lies offshore. Most submarine permafrost is relict terrestrial permafrost beneath the Arctic shelf seas, was inundated after the last glaciation, and has been warming and thawing ever since. It is a reservoir and confining layer for gas hydrates and has the potential to release greenhouse gases and affect global climate change. Furthermore, subsea permafrost thaw destabilizes coastal infrastructure. While numerous studies focus on its distribution and rate of thaw over glacial timescales, these studies have not been brought together and examined in their entirety to assess rates of thaw beneath the Arctic Ocean. In addition, there is still a large gap in our understanding of sub-aquatic permafrost processes on finer spatial and temporal scales. The degradation rate of subsea permafrost is influenced by the initial conditions upon submergence. Terrestrial permafrost that has already undergone warming, partial thawing or loss of ground ice may react differently to inundation by seawater compared to previously undisturbed ice-rich permafrost. Heat conduction models are sufficient to model the thaw of thick subsea permafrost from the bottom, but few studies have included salt diffusion for top-down chemical degradation in shallow waters characterized by mean annual cryotic conditions on the seabed. Simulating salt transport is critical for assessing degradation rates for recently inundated permafrost, which may accelerate in response to warming shelf waters, a lengthening open water season, and faster coastal erosion rates. In the nearshore zone, degradation rates are also controlled by seasonal processes like bedfast ice, brine injection, seasonal freezing under floating ice conditions and warm freshwater discharge from large rivers. The interplay of all these variables is complex and needs further research. To fill this knowledge gap, this thesis investigates sub-aquatic permafrost along the southern coast of the Bykovsky Peninsula in eastern Siberia. Sediment cores and ground temperature profiles were collected at a freshwater thermokarst lake and two thermokarst lagoons in 2017. At this site, the coastline is retreating, and seawater is inundating various types of permafrost: sections of ice-rich Pleistocene permafrost (Yedoma) cliffs at the coastline alternate with lagoons and lower elevation previously thawed and refrozen permafrost basins (Alases). Electrical resistivity surveys with floating electrodes were carried out to map ice-bearing permafrost and taliks (unfrozen zones in the permafrost, usually formed beneath lakes) along the diverse coastline and in the lagoons. Combined with the borehole data, the electrical resistivity results permit estimation of contemporary ice-bearing permafrost characteristics, distribution, and occasionally, thickness. To conceptualize possible geomorphological and marine evolutionary pathways to the formation of the observed layering, numerical models were applied. The developed model incorporates salt diffusion and seasonal dynamics at the seabed, including bedfast ice. Even along coastlines with mean annual non-cryotic boundary conditions like the Bykovsky Peninsula, the modelling results show that salt diffusion minimizes seasonal freezing of the seabed, leading to faster degradation rates compared to models without salt diffusion. Seasonal processes are also important for thermokarst lake to lagoon transitions because lagoons can generate cold hypersaline conditions underneath the ice cover. My research suggests that ice-bearing permafrost can form in a coastal lagoon environment, even under floating ice. Alas basins, however, may degrade more than twice as fast as Yedoma permafrost in the first several decades of inundation. In addition to a lower ice content compared to Yedoma permafrost, Alas basins may be pre-conditioned with salt from adjacent lagoons. Considering the widespread distribution of thermokarst in the Arctic, its integration into geophysical models and offshore surveys is important to quantify and understand subsea permafrost degradation and aggradation. Through numerical modelling, fieldwork, and a circum-Arctic review of subsea permafrost literature, this thesis provides new insights into sub-aquatic permafrost evolution in saline coastal environments.
KW  - permafrost
KW  - subsea
KW  - submarine
KW  - thermokarst
KW  - lagoons
KW  - salt diffusion
KW  - electrical resistivity
Y1  - 2020
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Westermann, Sebastian
A1  - Tronicke, Jens
A1  - Strauss, Jens
A1  - Schirrmeister, Lutz
A1  - Biskaborn, Boris
A1  - Liebner, Susanne
A1  - Maksimov, Georgii
A1  - Grigoriev, Mikhail N.
A1  - Grosse, Guido
T1  - Thermokarst lake to lagoon transitions in Eastern Siberia
BT  - do submerged taliks refreeze?
JF  - Journal of geophysical research : Earth surface
N2  - As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons, and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modeling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the center of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice-bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon had bedfast ice in spring. In bedfast ice areas, the electrical resistivity profiles suggested that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modeling showed that thermokarst lake taliks can refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0 degrees C. This occurs, because the top-down chemical degradation of newly formed ice-bearing permafrost is slower than the refreezing of the talik. Hence, lagoons may precondition taliks with a layer of ice-bearing permafrost before encroachment by the sea, and this frozen layer may act as a cap on gas migration out of the underlying talik.
KW  - thermokarst lake
KW  - talik
KW  - lagoon
KW  - subsea permafrost
KW  - salt diffusion
KW  - Siberia
Y1  - 2020
U6  - https://doi.org/10.1029/2019JF005424
SN  - 2169-9003
SN  - 2169-9011
VL  - 125
IS  - 10
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Angelopoulos, Michael
A1  - Westermann, Sebastian
A1  - Overduin, Pier Paul
A1  - Faguet, Alexey
A1  - Olenchenko, Vladimir
A1  - Grosse, Guido
A1  - Grigoriev, Mikhail N.
T1  - Heat and salt flow in subsea permafrost modeled with CryoGRID2
JF  - Journal of geophysical research : Earth surface
N2  - Thawing of subsea permafrost can impact offshore infrastructure, affect coastal erosion, and release permafrost organic matter. Thawing is usually modeled as the result of heat transfer, although salt diffusion may play an important role in marine settings. To better quantify nearshore subsea permafrost thawing, we applied the CryoGRID2 heat diffusion model and coupled it to a salt diffusion model. We simulated coastline retreat and subsea permafrost evolution as it develops through successive stages of a thawing sequence at the Bykovsky Peninsula, Siberia. Sensitivity analyses for seawater salinity were performed to compare the results for the Bykovsky Peninsula with those of typical Arctic seawater. For the Bykovsky Peninsula, the modeled ice-bearing permafrost table (IBPT) for ice-rich sand and an erosion rate of 0.25m/year was 16.7 m below the seabed 350m offshore. The model outputs were compared to the IBPT depth estimated from coastline retreat and electrical resistivity surveys perpendicular to and crossing the shoreline of the Bykovsky Peninsula. The interpreted geoelectric data suggest that the IBPT dipped to 15-20m below the seabed at 350m offshore. Both results suggest that cold saline water forms beneath grounded ice and floating sea ice in shallow water, causing cryotic benthic temperatures. The freezing point depression produced by salt diffusion can delay or prevent ice formation in the sediment and enhance the IBPT degradation rate. Therefore, salt diffusion may facilitate the release of greenhouse gasses to the atmosphere and considerably affect the design of offshore and coastal infrastructure in subsea permafrost areas.
KW  - subsea permafrost
KW  - salt diffusion
KW  - CryoGRID
KW  - Lena Delta
KW  - Bykovsky Peninsula
KW  - electrical resistivity
Y1  - 2019
U6  - https://doi.org/10.1029/2018JF004823
SN  - 2169-9003
SN  - 2169-9011
VL  - 124
IS  - 4
SP  - 920
EP  - 937
PB  - American Geophysical Union
CY  - Hoboken
ER  - 
TY  - THES
A1  - Angermann, Lisa
T1  - Hillslope-stream connectivity across scales
T1  - Mehrskalige Untersuchung der Hang-Bach Konnektivität
N2  - The concept of hydrologic connectivity summarizes all flow processes that link separate regions of a landscape. As such, it is a central theme in the field of catchment hydrology, with influence on neighboring disciplines such as ecology and geomorphology. It is widely acknowledged to be an important key in understanding the response behavior of a catchment and has at the same time inspired research on internal processes over a broad range of scales. From this process-hydrological point of view, hydrological connectivity is the conceptual framework to link local observations across space and scales.
This is the context in which the four studies this thesis comprises of were conducted. The focus was on structures and their spatial organization as important control on preferential subsurface flow. Each experiment covered a part of the conceptualized flow path from hillslopes to the stream: soil profile, hillslope, riparian zone, and stream.
For each study site, the most characteristic structures of the investigated domain and scale, such as slope deposits and peat layers were identified based on preliminary or previous investigations or literature reviews. Additionally, further structural data was collected and topographical analyses were carried out. Flow processes were observed either based on response observations (soil moisture changes or discharge patterns) or direct measurement (advective heat transport). Based on these data, the flow-relevance of the characteristic structures was evaluated, especially with regard to hillslope to stream connectivity.
Results of the four studies revealed a clear relationship between characteristic spatial structures and the hydrological behavior of the catchment. Especially the spatial distribution of structures throughout the study domain and their interconnectedness were crucial for the establishment of preferential flow paths and their relevance for large-scale processes. Plot and hillslope-scale irrigation experiments showed that the macropores of a heterogeneous, skeletal soil enabled preferential flow paths at the scale of centimeters through the otherwise unsaturated soil. These flow paths connected throughout the soil column and across the hillslope and facilitated substantial amounts of vertical and lateral flow through periglacial slope deposits.
In the riparian zone of the same headwater catchment, the connectivity between hillslopes and stream was controlled by topography and the dualism between characteristic subsurface structures and the geomorphological heterogeneity of the stream channel. At the small scale (1 m to 10 m) highest gains always occurred at steps along the longitudinal streambed profile, which also controlled discharge patterns at the large scale (100 m) during base flow conditions (number of steps per section). During medium and high flow conditions, however, the impact of topography and parafluvial flow through riparian zone structures prevailed and dominated the large-scale response patterns. 
In the streambed of a lowland river, low permeability peat layers affected the connectivity between surface water and groundwater, but also between surface water and the hyporheic zone. The crucial factor was not the permeability of the streambed itself, but rather the spatial arrangement of flow-impeding peat layers, causing increased vertical flow through narrow “windows” in contrast to predominantly lateral flow in extended areas of high hydraulic conductivity sediments. 
These results show that the spatial organization of structures was an important control for hydrological processes at all scales and study areas. In a final step, the observations from different scales and catchment elements were put in relation and compared. The main focus was on the theoretical analysis of the scale hierarchies of structures and processes and the direction of causal dependencies in this context. Based on the resulting hierarchical structure, a conceptual framework was developed which is capable of representing the system’s complexity while allowing for adequate simplifications.
The resulting concept of the parabolic scale series is based on the insight that flow processes in the terrestrial part of the catchment (soil and hillslopes) converge. This means that small-scale processes assemble and form large-scale processes and responses. Processes in the riparian zone and the streambed, however, are not well represented by the idea of convergence. Here, the large-scale catchment signal arrives and is modified by structures in the riparian zone, stream morphology, and the small-scale interactions between surface water and groundwater. Flow paths diverge and processes can better be represented by proceeding from large scales to smaller ones. The catchment-scale representation of processes and structures is thus the conceptual link between terrestrial hillslope processes and processes in the riparian corridor.
N2  - Das Konzept der hydrologischen Konnektivität umfasst alle Fließprozesse, welche verschiedene Bereiche einer Landschaft verbinden. Als solches ist es ein zentrales Thema in dem Forschungsbereich der Einzugsgebietshydrologie und beeinflusst auch benachbarte Disziplinen wie die Ökologie oder die Geomorphologie. Es ist allgemein akzeptiert, dass das Konzept der Konnektivität ein wichtiger Schlüssel zum Verständnis von Einzugsgebietsdynamiken ist, gleichzeitig inspiriert es die Erforschung interner Prozesse auf verschiedenen Skalen. Von dieser prozesshydrologischen Perspektive gesehen, bietet Konnektivität einen konzeptionellen Rahmen, um lokale Beobachtungen über Raum und Skalen miteinander in Verbindung zu setzen.
In diesem Kontext stehen die vier Studien dieser Doktorarbeit. Der Fokus lag dabei auf räumlichen Strukturen als wichtigem Kontrollfaktor für präferentielle Fließpfade als spezieller Form unterirdischer Fließprozesse. Die Experimente deckten dabei je einen Abschnitt des konzeptionellen Fließweges vom Hang zum Bach exemplarisch ab: Bodenprofil und Hang, Hang und Auenbreich, und Bachbett.
Für alle vier Studien wurden zunächst charakteristische Strukturen des Untersuchungsgebietes wie Schuttablagerungen am Hang oder Torfschichten im Flussbett auf Basis vorausgehender Untersuchungen und Literaturrecherchen identifiziert. Zusätzlich wurden weitere strukturelle Daten erfasst und digitale Geländemodelle ausgewertet. Anschließend wurde die Prozessrelevanz dieser Strukturen, vor allem im Hinblick auf die Hang-Bach-Konnektivität, untersucht.
Die Ergebnisse der einzelnen Studien zeigten eine deutliche Verbindung zwischen den charakteristischen räumlichen Strukturen und dem hydrologischen Verhalten des untersuchten Gebietes. Insbesondere die räumliche Anordnung von Strukturen, d.h. die räumliche Verteilung und der Grad der Konnektivität der Strukturen, war ausschlaggebend für die Ausbildung präferenzieller Fließpfade und deren Relevanz für größerskalige Prozesse. Die räumliche Organisation von Strukturen war in allen Untersuchungsgebieten ein wichtiger Kontrollfaktor für hydrologische Prozesse.
Die Beobachtungen auf verschiedenen Skalen und verschiedener Fließpfadabschnitte wurden miteinander in Verbindung gesetzt und verglichen. Besonderes Augenmerk lag dabei auf der theoretischen Analyse der Skalenhierarchie von Strukturen und Prozessen und der Richtung der Kausalität in diesem Zusammenhang. Auf dieser Grundlage wurde als Synthese der einzelnen Studien ein Konzept entwickelt, welches in der Lage ist, die Komplexität eines Einzugsgebietes abzubilden und gleichzeitig adequate Vereinfachungen zuzulassen.
Diese Konzept der parabelförmigen Skalenabfolge beruht auf der Erkenntnis, dass Fließprozesse im terrestrischen Bereich eines Einzugsgebietes, also im Boden und den Hängen, vorwiegend konvergieren und sich von der kleinen Skala zur größeren hin zusammenfügen. Die Prozesse in der Aue und dem Bachbett werden von diesem Prinzip der Konvergenz allerding nicht abgebildet. Die in den Böden und an den Hängen erzeugten Fließmuster des Einzugsgebiets werden von den Strukturen in der Aue, der Morphologie des Baches und den kleinskaligen Wechselwirkungen zwischen Fließgewässer und Sediment überprägt. Die Fließprozesse divergieren, und eine Beschreibung von der großen Skala hin zur kleineren ist hier besser geeignet. Die räumlich diskrete oder konzeptionelle Darstellung von Prozessen auf der Einzugsgebietsskala bietet so die Verbindung zwischen terrestrischer Hanghydrologie und der bachseitigen Auenhydrologie.
KW  - catchment hydrology
KW  - hillslope hydrology
KW  - riparian zone
KW  - hyporheic zone
KW  - Einzugsgebietshydrologie
KW  - Hanghydrologie
KW  - Auenbereich
KW  - hyporheische Zone
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-424542
ER  - 
TY  - JOUR
A1  - Angermann, Lisa
A1  - Jackisch, Conrad
A1  - Allroggen, Niklas
A1  - Sprenger, Matthias
A1  - Zehe, Erwin
A1  - Tronicke, Jens
A1  - Weiler, Markus
A1  - Blume, Theresa
T1  - Form and function in hillslope hydrology: characterization of subsurface flow based on response observations
JF  - Hydrology and earth system sciences : HESS
N2  - The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al. (2017).
Y1  - 2017
U6  - https://doi.org/10.5194/hess-21-3727-2017
SN  - 1027-5606
SN  - 1607-7938
VL  - 21
SP  - 3727
EP  - 3748
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - THES
A1  - Anis, Muhammad Rehan
T1  - Climate change effects on overland flow
Y1  - 2013
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Anoop, A.
A1  - Prasad, S.
A1  - Basavaiah, Nathani
A1  - Brauer, Achim
A1  - Shahzad, F.
A1  - Deenadayalan, K.
T1  - Tectonic versus climate influence on landscape evolution: A case study from the upper Spiti valley, NW Himalaya
JF  - Geomorphology : an international journal on pure and applied geomorphology
N2  - We have undertaken structural, geomorphological, and morphometric analyses to investigate the role of tectonism and climate in the landscape evolution in the upper Spiti valley, NW Himalayas. Geomorphometric analyses coupled with field investigations reveal active tectonic deformation in the Spiti region. The calculated geomorphic indices (steepness, concavity and Hack) demonstrate uplift/subsidence along the Kaurik-Chango fault, whereas transverse topographic index (T-index) reveals basin tilting associated with active faulting near Hansa and Lingti valley. Investigation of well-dated Mane palaeolake sediments also provides evidence of regional tectonic instability. Four episodes (ca. 7.8, 7.4, 6.5 and 6.1 cal ka) of neotectonic activity have been identified during the period of the lake's existence. We have also compiled data on the regional climate variability and compared it with the age of the Mane palaeo-landslide. Our results indicate that the landslide occurred towards the end of the early Holocene intensified monsoon phase and is located near an active fault. Our data on regional tectonic instability and the coincidences of modern and palaeo-landslides with zones of active deformation suggest that tectonism is an important factor governing landscape stability in the Spiti region.
KW  - Geomorphic indices
KW  - Holocene
KW  - Palaeo-lake sediments
KW  - Palaeo-landslides
KW  - Monsoon
Y1  - 2012
U6  - https://doi.org/10.1016/j.geomorph.2011.10.028
SN  - 0169-555X
VL  - 145
IS  - 4
SP  - 32
EP  - 44
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Anoop, Ambili
A1  - Prasad, S.
A1  - Plessen, Birgit
A1  - Basavaiah, Nathani
A1  - Gaye, B.
A1  - Naumann, R.
A1  - Menzel, P.
A1  - Weise, S.
A1  - Brauer, Achim
T1  - Palaeoenvironmental implications of evaporative gaylussite crystals from Lonar Lake, central India
JF  - Journal of quaternary science
N2  - We have undertaken petrographic, mineralogical, geochemical and isotopic investigations on carbonate minerals found within a 10-m-long core from Lonar Lake, central India, with the aim of evaluating their potential as palaeoenvironmental proxies. The core encompasses the entire Holocene and is the first well-dated high-resolution record from central India. While calcite and/or aragonite were found throughout the core, the mineral gaylussite was found only in two specific intervals (46303890 and 2040560 cal a BP). Hydrochemical and isotope data from inflowing streams and lake waters indicate that evaporitic processes play a dominant role in the precipitation of carbonates within this lake. Isotopic (18O and 13C) studies on the evaporative gaylussite crystals and residual bulk carbonates (calcite) from the long core show that evaporation is the major control on 18O enrichment in both the minerals. However, in case of 13C additional mechanisms, for example methanogenesis (gaylussite) and phytoplankton productivity (calcium carbonate), play an additional important role in some intervals. We also discuss the relevance of our investigation for palaeoclimate reconstruction and late Holocene monsoon variability.
KW  - evaporites
KW  - gaylussite
KW  - isotopes
KW  - Lonar Lake
KW  - monsoon
Y1  - 2013
U6  - https://doi.org/10.1002/jqs.2625
SN  - 0267-8179
VL  - 28
IS  - 4
SP  - 349
EP  - 359
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Anoop, Ambili
A1  - Prasad, Sushma
A1  - Krishnan, R.
A1  - Naumann, Rudolf
A1  - Dulski, Peter
T1  - Intensified monsoon and spatiotemporal changes in precipitation patterns in the NW Himalaya during the early-mid holocene
JF  - Quaternary international : the journal of the International Union for Quaternary Research
N2  - We have undertaken a high resolution palaeoclimate reconstruction on radiocarbon dated palaeolake sediments from the Spiti valley, NW Himalaya. This site lies in the climatically sensitive winter westerlies and Indian Summer Monsoon (ISM) transitional regime and provides an opportunity to reconstruct the precipitation seasonality, and extreme precipitation events that are characterised by intensified erosion. The lake sediments reveal distinct lithofacies that provide evidence of changes in depositional environment and climate during early to mid Holocene (8.7-6.1 cal ka BP). We have identified three stages during the period of lake's existence: the Stage I (8.7-7.6 cal ka BP) is marked by lake establishment; Stage II (similar to 7.6-6.8 cal ka BP) by sustained cooler periods and weakened summer monsoon, and Stage III (similar to 6.8-6.1 cal ka BP) by a shift from colder to warmer climate with stronger ISM. We have identified several short term cooler periods at ca. 8.7, 8.5, 8.3 and 7.2-6.9 cal ka BP. Based on an overview of regional climate records we show that there is an abrupt switch in precipitation seasonality ca. 6.8 cal ka BP that is followed by the onset of the intensified monsoon in the NW Himalaya. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.
Y1  - 2013
U6  - https://doi.org/10.1016/j.quaint.2013.08.014
SN  - 1040-6182
VL  - 313
SP  - 74
EP  - 84
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - THES
A1  - Antonoglou, Nikolaos
T1  - GNSS-based remote sensing: Innovative observation of key hydrological parameters in the Central Andes
T1  - GNSS-basierte Fernerkundung: Innovative Beobachtung der wichtigsten hydrologischen Parameter in den zentralen Anden
N2  - The Central Andean region is characterized by diverse climate zones with sharp transitions between them. In this work, the area of interest is the South-Central Andes in northwestern Argentina that borders with Bolivia and Chile. The focus is the observation of soil moisture and water vapour with Global Navigation Satellite System (GNSS) remote-sensing methodologies. Because of the rapid temporal and spatial variations of water vapour and moisture circulations, monitoring this part of the hydrological cycle is crucial for understanding the mechanisms that control the local climate. Moreover, GNSS-based techniques have previously shown high potential and are appropriate for further investigation. This study includes both logistic-organization effort and data analysis. As for the prior, three GNSS ground stations were installed in remote locations in northwestern Argentina to acquire observations, where there was no availability of third-party data.

The methodological development for the observation of the climate variables of soil moisture and water vapour is independent and relies on different approaches. The soil-moisture estimation with GNSS reflectometry is an approximation that has demonstrated promising results, but it has yet to be operationally employed. Thus, a more advanced algorithm that exploits more observations from multiple satellite constellations was developed using data from two pilot stations in Germany. Additionally, this algorithm was slightly modified and used in a sea-level measurement campaign. Although the objective of this application is not related to monitoring hydrological parameters, its methodology is based on the same principles and helps to evaluate the core algorithm. On the other hand, water-vapour monitoring with GNSS observations is a well-established technique that is utilized operationally. Hence, the scope of this study is conducting a meteorological analysis by examining the along-the-zenith air-moisture levels and introducing indices related to the azimuthal gradient.

The results of the experiments indicate higher-quality soil moisture observations with the new algorithm. Furthermore, the analysis using the stations in northwestern Argentina illustrates the limits of this technology because of varying soil conditions and shows future research directions. The water-vapour analysis points out the strong influence of the topography on atmospheric moisture circulation and rainfall generation. Moreover, the GNSS time series allows for the identification of seasonal signatures, and the azimuthal-gradient indices permit the detection of main circulation pathways.
N2  - Die Zentralanden sind eine Region, in der verschiedene Klimazonen nur durch kurze Übergänge gekennzeichnet sind. Der geographische Schwerpunkt dieser Arbeit liegt in den südlichen Zentralanden im Grenzgebiet zwischen Argentinien, Bolivien und Chile, und der wissenschaftliche Schwerpunkt ist in der Überwachung der Bodenfeuchtigkeit und des Wasserdampfs mit Fernerkundungsmethoden des Globales Navigationssatellitensystem (Global Navigation Satellite System - GNSS) angesiedelt. Wegen der raschen zeitlichen und räumlichen Schwankungen des Wasserdampfs und den damit häufig verbundenen Niederschlägen und der Feuchtigkeitszirkulation ist die Beobachtung dieses Teils des hydrologischen Zyklus von entscheidender Bedeutung für das Verständnis des lokalen Klimas. Darüber hinaus haben GNSS-gestützte Techniken in anderen Studien bereits ein hohes Potenzial gezeigt, erfordern aber in einigen Bereichen weitere Untersuchungen. Diese Studie umfasst sowohl logistischen Aufwand als auch Datenanalyse. Dazu wurden drei GNSS-Bodenstationen in abgelegenen Orten im Nordwesten Argentiniens installiert, um Beobachtungen zu sammeln, da dort keine externen Daten verfügbar waren.

Die methodische Entwicklung für die Beobachtung der Klimavariablen Bodenfeuchtigkeit und Wasserdampfs ist unabhängig voneinander. Die Messung der Bodenfeuchte mit Hilfe der GNSS-Reflektometrie ist eine Annäherung, die vielversprechende Ergebnisse erbracht hat, aber bisher noch nicht operationell eingesetzt wurde. Daher wurde ein fortschrittlicherer Algorithmus entwickelt, der Beobachtungen von mehreren Satellitenkonstellationen nutzt und unter anderem Daten von zwei Pilotstationen in Deutschland verwendet. Außerdem wurde dieser Algorithmus leicht modifiziert und in einer Meeresspiegelmesskampagne eingesetzt. Obwohl diese Andwendung nicht direkt mit der Überwachung hydrologischer Parameter zusammenhängt, basiert die Methodik auf denselben Prinzipien und hilft bei der Bewertung des entwickelten Algorithmus. Auf der anderen Seite ist die Überwachung des Wasserdampfs mit GNSS-Beobachtungen eine anerkannte Technik, die in der Praxis bereits seit mehreren Jahren eingesetzt wird. Diese Studie befasst sich daher mit der Durchführung einer meteorologischen Analyse der Luftfeuchtigkeitswerte entlang des Zenits und der Entwicklung von klimatischen Indizes, die sich auf den azimutalen Gradienten beziehen.

Die Ergebnisse der Experimente zeigen, dass die Qualität der Bodenfeuchtebeobachtungen mit dem neuen Algorithmus vielversprechend und besser sind. Darüber hinaus zeigt die Analyse anhand der Stationen im nordwesten Argentiniens die Grenzen dieser Technologie aufgrund der sehr unterschiedlichen Bodenbedingungen auf und gibt mögliche zukünftige Forschungsrichtung an. Die Wasserdampfanalyse verdeutlicht den Einfluss der Topographie auf die Luftfeuchtigkeit und der Regenmenge. Außerdem ermöglichen die GNSS-Zeitreihen die Identifizierung der jahreszeitlichen Signaturen, und Messungen der azimutal Gradienten erlauben die Erkennung der wichtigsten Zirkulationswege.
KW  - remote sensing
KW  - GNSS
KW  - GPS
KW  - water vapour
KW  - soil moisture
KW  - Central Andes
KW  - zentrale Anden
KW  - globales Navigationssatellitensystem
KW  - globales Positionsbestimmungssystem
KW  - Fernerkundung
KW  - Bodenfeuchtigkeit
KW  - Wasserdampf
Y1  - 2024
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-628256
ER  - 
TY  - JOUR
A1  - Apaestegui, James
A1  - Cruz, Francisco William
A1  - Vuille, Mathias
A1  - Fohlmeister, Jens Bernd
A1  - Carlo Espinoza, Jhan
A1  - Sifeddine, Abdelfettah
A1  - Strikis, Nicolas
A1  - Guyot, Jean Loup
A1  - Ventura, Roberto
A1  - Cheng, Hai
A1  - Edwards, R. Lawrence
T1  - Precipitation changes over the eastern Bolivian Andes inferred from speleothem (delta O-18) records for the last 1400 years
JF  - Earth & planetary science letters
N2  - Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA.
KW  - speleothems
KW  - stable isotopes
KW  - MCA
KW  - LIA
KW  - Bolivia
KW  - South American Monsoon
Y1  - 2018
U6  - https://doi.org/10.1016/j.epsl.2018.04.048
SN  - 0012-821X
SN  - 1385-013X
VL  - 494
SP  - 124
EP  - 134
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aramayo, Alejandro
A1  - Guzman, Silvina
A1  - Hongn, Fernando D.
A1  - del Papa, Cecilia
A1  - Montero-Lopez, Carolina
A1  - Sudo, Masafumi
T1  - A Middle Miocene (13.5-12 Ma) deformational event constrained by volcanism along the Puna-Eastern Cordillera border, NW Argentina
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - The features of Middle Miocene deposits in the Puna-Eastern Cordillera transition (Valles Calchaquies) indicate that Cenozoic deformation, sedimentation and volcanism follow a complex spatiotemporal relationship. The intense volcanic activity recorded in the eastern Puna border between 14 and 11.5 Ma coincides with the occurrence of one of the most important deformation events of the Neogene tectonic evolution in the region. Studies performed across the Puna-Eastern Cordillera transition show different relationships between volcanic deposits of ca. 13.5-12.1 Ma and the Oligocene-Miocene Angastaco Formation. In this paper we describe the ash-flow tuff deposits which are the first of this type found concordant in the sedimentary fill of Valles Calchaquies. Several analyses performed on these pyroclastic deposits allow a correlation to be made with the Alto de Las Lagunas Ignimbrite (ca. 13.5 Ma) of the Pucarilla-Cerro Tipillas Volcanic Complex located in the Puna. Outcrops of the ca. 13.5 Ma pyroclastic deposits are recognised within the Puna and the Valle Calchaqui. However, in the southern prolongation of the Valle de Hualfin (Tiopampa-Pucarilla depression) that separates the Puna from the Valle Calchaqui at these latitudes, these deposits are partially eroded and buried, and thus their occurrence is recorded only by abundant volcanic clasts included in conglomerates of the Angastaco Formation. The sedimentation of the Angastaco Formation was aborted at ca. 12 Ma in the Tiopampa-Pucarilla depression by the Pucarilla Ignimbrite, which unconformably covers the synorogenic units. On the contrary, in the Valle Calchaqui the sedimentation of the Angastaco Formation continued until the Late Miocene. The different relationships between the Miocene Angastaco Formation and the ignimbrites with ages of ca. 13.5 and ca. 12 Ma reveal that in this short period (-1.5 m.y.) a significant deformation event took place and resulted in marked palaeogeographic changes, as evidenced by stratigraphic-sedimentological and chronological records in the Angastaco Formation. (C) 2017 Elsevier B.V. All rights reserved.
KW  - Angastaco Formation
KW  - Miocene deformation
KW  - Alto de Las Lagunas Ignimbrite
KW  - Luingo caldera
KW  - Foreland
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2017.02.018
SN  - 0040-1951
SN  - 1879-3266
VL  - 703
SP  - 9
EP  - 22
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Araya Vargas, Jaime Andrés
A1  - Meqbel, Naser M.
A1  - Ritter, Oliver
A1  - Brasse, H.
A1  - Weckmann, Ute
A1  - Yanez, Gonzalo
A1  - Godoy, B.
T1  - Fluid Distribution in the Central Andes Subduction Zone Imaged With Magnetotellurics
JF  - Journal of geophysical research : Solid earth
N2  - We present a model of the electrical resistivity structure of the lithosphere in the Central Andes between 20 degrees and 24 degrees S from 3-D inversion of 56 long-period magnetotelluric sites. Our model shows a complex resistivity structure with significant variability parallel and perpendicular to the trench direction. The continental forearc is characterized mainly by high electrical resistivity (>1,000m), suggesting overall low volumes of fluids. However, low resistivity zones (LRZs, <5m) were found in the continental forearc below areas where major trench-parallel faults systems intersect NW-SE transverse faults. Forearc LRZs indicate circulation and accumulation of fluids in highly permeable fault zones. The continental crust along the arc shows three distinctive resistivity domains, which coincide with segmentation in the distribution of volcanoes. The northern domain (20 degrees-20.5 degrees S) is characterized by resistivities >1,000m and the absence of active volcanism, suggesting the presence of a low-permeability block in the continental crust. The central domain (20.5 degrees-23 degrees S) exhibits a number of LRZs at varying depths, indicating different levels of a magmatic plumbing system. The southern domain (23 degrees-24 degrees S) is characterized by resistivities >1,000m, suggesting the absence of large magma reservoirs below the volcanic chain at crustal depths. Magma reservoirs located below the base of the crust or in the backarc may fed active volcanism in the southern domain. In the subcontinental mantle, the model exhibits LRZs in the forearc mantle wedge and above clusters of intermediate-depth seismicity, likely related to fluids produced by serpentinization of the mantle and eclogitization of the slab, respectively.
KW  - Subduction Zone
KW  - Central Andes
KW  - Magnetotellurics
KW  - Seismotectonic segmentation
KW  - Fluid processes
Y1  - 2019
U6  - https://doi.org/10.1029/2018JB016933
SN  - 2169-9313
SN  - 2169-9356
VL  - 124
IS  - 4
SP  - 4017
EP  - 4034
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - THES
A1  - Arboleda Zapata, Mauricio
T1  - Adapted inversion strategies for electrical resistivity data to explore layered near-surface environments
N2  - The electrical resistivity tomography (ERT) method is widely used to investigate geological, geotechnical, and hydrogeological problems in inland and aquatic environments (i.e., lakes, rivers, and seas). The objective of the ERT method is to obtain reliable resistivity models of the subsurface that can be interpreted in terms of the subsurface structure and petrophysical properties. The reliability of the resulting resistivity models depends not only on the quality of the acquired data, but also on the employed inversion strategy. Inversion of ERT data results in multiple solutions that explain the measured data equally well. Typical inversion approaches rely on different deterministic (local) strategies that consider different smoothing and damping strategies to stabilize the inversion. However, such strategies suffer from the trade-off of smearing possible sharp subsurface interfaces separating layers with resistivity contrasts of up to several orders of magnitude. When prior information (e.g., from outcrops, boreholes, or other geophysical surveys) suggests sharp resistivity variations, it might be advantageous to adapt the parameterization and inversion strategies to obtain more stable and geologically reliable model solutions. Adaptations to traditional local inversions, for example, by using different structural and/or geostatistical constraints, may help to retrieve sharper model solutions. In addition, layer-based model parameterization in combination with local or global inversion approaches can be used to obtain models with sharp boundaries.

In this thesis, I study three typical layered near-surface environments in which prior information is used to adapt 2D inversion strategies to favor layered model solutions. In cooperation with the coauthors of Chapters 2-4, I consider two general strategies. Our first approach uses a layer-based model parameterization and a well-established global inversion strategy to generate ensembles of model solutions and assess uncertainties related to the non-uniqueness of the inverse problem. We apply this method to invert ERT data sets collected in an inland coastal area of northern France (Chapter~2) and offshore of two Arctic regions (Chapter~3). Our second approach consists of using geostatistical regularizations with different correlation lengths. We apply this strategy to a more complex subsurface scenario on a local intermountain alluvial fan in southwestern Germany (Chapter~4). Overall, our inversion approaches allow us to obtain resistivity models that agree with the general geological understanding of the studied field sites. These strategies are rather general and can be applied to various geological environments where a layered subsurface structure is expected. The flexibility of our strategies allows adaptations to invert other kinds of geophysical data sets such as seismic refraction or electromagnetic induction methods, and could be considered for joint inversion approaches.
N2  - Die ERT-Methode (Electrical Resistivity Tomography) wird häufig zur Untersuchung geologischer, geotechnischer und hydrogeologischer Probleme im Binnenland und in Gewässern wie beispielsweise Seen, Flüssen oder dem Meer eingesetzt. Das Ziel der ERT-Methode ist es, zuverlässige Widerstandsmodelle des Untergrunds zu erhalten, die in Bezug auf die Struktur des Untergrundes und dessen petrophysikalischer Eigenschaften interpretiert werden können. Die Zuverlässigkeit der resultierenden Widerstandsmodelle hängt nicht nur von der Qualität der erfassten Daten ab, sondern auch von der angewendeten Inversionsstrategie. Die Inversion von ERT-Daten führt zu mehreren Lösungen, die die gemessenen Daten gleich gut erklären. Typische Inversionsansätze basieren auf verschiedenen deterministischen (lokalen) Strategien, die verschiedene Glättungs- und Dämpfungsstrategien berücksichtigen, um die Inversion zu stabilisieren. Diese Strategien haben jedoch den Nachteil, möglicherweise auftretende scharfe Grenzflächen zu verwischen. Es gibt jedoch Szenarien, in denen der Untergrund durch Schichten mit scharfen Grenzflächen gekennzeichnet ist, die Schichten mit hohem Widerstandskontrast (z. B. bis zu mehreren Größenordnungen) voneinander trennen. Wenn Vorwissen (z. B. aus Aufschlüssen, Bohrungen oder anderen geophysikalischen Untersuchungen) auf scharfe Widerstandsvariationen hindeutet, kann es von Vorteil sein, die Parametrisierungs- und Inversionsstrategien anzupassen, um stabilere und geologisch zuverlässige Modelllösungen zu erhalten. Anpassungen traditioneller lokaler Inversionen, beispielweise durch die Verwendung verschiedener struktureller und/oder geostatistischer Bedingungen, können helfen, schärfere Modelllösungen zu erhalten. Zusätzlich kann eine schichtbasierte Modellparametrisierung in Kombination mit lokalen oder globalen Inversionsansätzen verwendet werden, um Modelle mit scharfen Grenzen zu erhalten.

In dieser Arbeit habe ich drei typische geschichtete oberflächennahe Umgebungen untersucht, in denen Vorabinformationen verwendet werden, um 2D-Inversionsstrategien so anzupassen, dass geschichtete Untergrundlösungen bevorzugt werden. In Zusammenarbeit mit den Co-Autoren der Kapitel 2-4 habe ich zwei allgemeine Strategien in Betracht gezogen. Unser erster Ansatz verwendet eine schichtbasierte Modellparametrisierung und eine gut etablierte globale Inversionsstrategie. Diese Strategie erzeugt Ensembles von Modelllösungen mithilfe derer die Unsicherheiten im Zusammenhang der Nicht-Eindeutigkeit des inversen Problems bewertet werden können. Wir wenden diese Methode an, um ERT-Datensätze zu invertieren, die in einem Binnenküstengebiet in Nordfrankreich (Kapitel 2) und vor der Küste zweier arktischer Regionen (Kapitel 3) gesammelt wurden. Unser zweiter Ansatz besteht darin, geostatistische Regularisierungen mit unterschiedlichen Korrelationslängen zu verwenden. Wir wenden diese Strategie auf ein komplexeres Untergrundszenario an, das sich auf einen lokalen Schwemmfächer in einem Mittelgebirge im Südwesten Deutshclands umfasst (Kapitel 4). Insgesamt ermöglichen uns unsere Inversionsansätze, Widerstandsmodelle zu erhalten, die mit dem allgemeinen geologischen Verständnis der untersuchten Feldstandorte übereinstimmen. Diese Strategien sind allgemeingültig und können in verschiedenen geologischen Umgebungen angewandt werden, in denen eine geschichtete Struktur des Untergrunds zu erwarten ist. Zudem erlaubt es die Flexibilität unserer Strategien, dass diese an die Inversion anderer geophysikalischer Datensätze wie seismischer Refraktionsmessungen oder elektromagentischer Induktionsverfahren angepasst werden können. Außerdem könnten solche Strategien für gemeinsame Inversionsansätze in Betracht gezogen werden.
KW  - Near-surface geophysics
KW  - Electrical resistivity tomography
KW  - Non-uniqueness
KW  - Global inversion
KW  - Particle swarm optimization
KW  - Ensemble analysis
KW  - Oberflächennahe Geophysik
KW  - Tomographie des elektrischen Widerstands
KW  - Nicht-Einmaligkeit
KW  - Globale Inversion
KW  - Partikelschwarm-Optimierung
KW  - Ensemble-Analyse
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-581357
ER  - 
TY  - GEN
A1  - Arboleda-Zapata, Mauricio
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Grosse, Guido
A1  - Jones, Benjamin M.
A1  - Tronicke, Jens
T1  - Exploring the capabilities of electrical resistivity tomography to study subsea permafrost
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Sea level rise and coastal erosion have inundated large areas of Arctic permafrost. Submergence by warm and saline waters increases the rate of inundated permafrost thaw compared to sub-aerial thawing on land. Studying the contact between the unfrozen and frozen sediments below the seabed, also known as the ice-bearing permafrost table (IBPT), provides valuable information to understand the evolution of sub-aquatic permafrost, which is key to improving and understanding coastal erosion prediction models and potential greenhouse gas emissions. In this study, we use data from 2D electrical resistivity tomography (ERT) collected in the nearshore coastal zone of two Arctic regions that differ in their environmental conditions (e.g., seawater depth and resistivity) to image and study the subsea permafrost. The inversion of 2D ERT data sets is commonly performed using deterministic approaches that favor smoothed solutions, which are typically interpreted using a user-specified resistivity threshold to identify the IBPT position. In contrast, to target the IBPT position directly during inversion, we use a layer-based model parameterization and a global optimization approach to invert our ERT data. This approach results in ensembles of layered 2D model solutions, which we use to identify the IBPT and estimate the resistivity of the unfrozen and frozen sediments, including estimates of uncertainties. Additionally, we globally invert 1D synthetic resistivity data and perform sensitivity analyses to study, in a simpler way, the correlations and influences of our model parameters. The set of methods provided in this study may help to further exploit ERT data collected in such permafrost environments as well as for the design of future field experiments.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1285 
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571234
SN  - 1866-8372
IS  - 1285
SP  - 4423
EP  - 4445
ER  - 
TY  - JOUR
A1  - Arboleda-Zapata, Mauricio
A1  - Angelopoulos, Michael
A1  - Overduin, Pier Paul
A1  - Grosse, Guido
A1  - Jones, Benjamin M.
A1  - Tronicke, Jens
T1  - Exploring the capabilities of electrical resistivity tomography to study subsea permafrost
JF  - The Cryosphere
N2  - Sea level rise and coastal erosion have inundated large areas of Arctic permafrost. Submergence by warm and saline waters increases the rate of inundated permafrost thaw compared to sub-aerial thawing on land. Studying the contact between the unfrozen and frozen sediments below the seabed, also known as the ice-bearing permafrost table (IBPT), provides valuable information to understand the evolution of sub-aquatic permafrost, which is key to improving and understanding coastal erosion prediction models and potential greenhouse gas emissions. In this study, we use data from 2D electrical resistivity tomography (ERT) collected in the nearshore coastal zone of two Arctic regions that differ in their environmental conditions (e.g., seawater depth and resistivity) to image and study the subsea permafrost. The inversion of 2D ERT data sets is commonly performed using deterministic approaches that favor smoothed solutions, which are typically interpreted using a user-specified resistivity threshold to identify the IBPT position. In contrast, to target the IBPT position directly during inversion, we use a layer-based model parameterization and a global optimization approach to invert our ERT data. This approach results in ensembles of layered 2D model solutions, which we use to identify the IBPT and estimate the resistivity of the unfrozen and frozen sediments, including estimates of uncertainties. Additionally, we globally invert 1D synthetic resistivity data and perform sensitivity analyses to study, in a simpler way, the correlations and influences of our model parameters. The set of methods provided in this study may help to further exploit ERT data collected in such permafrost environments as well as for the design of future field experiments.
Y1  - 2022
U6  - https://doi.org/10.5194/tc-16-4423-2022
SN  - 1994-0424
VL  - 16
SP  - 4423
EP  - 4445
PB  - Copernicus
CY  - Katlenburg-Lindau
ER  - 
TY  - JOUR
A1  - Arboleda-Zapata, Mauricio
A1  - Guillemoteau, Julien
A1  - Tronicke, Jens
T1  - A comprehensive workflow to analyze ensembles of globally inverted 2D electrical resistivity models
JF  - Journal of applied geophysics
N2  - Electrical resistivity tomography (ERT) aims at imaging the subsurface resistivity distribution and provides valuable information for different geological, engineering, and hydrological applications. To obtain a subsurface resistivity model from measured apparent resistivities, stochastic or deterministic inversion procedures may be employed. Typically, the inversion of ERT data results in non-unique solutions; i.e., an ensemble of different models explains the measured data equally well. In this study, we perform inference analysis of model ensembles generated using a well-established global inversion approach to assess uncertainties related to the nonuniqueness of the inverse problem. Our interpretation strategy starts by establishing model selection criteria based on different statistical descriptors calculated from the data residuals. Then, we perform cluster analysis considering the inverted resistivity models and the corresponding data residuals. Finally, we evaluate model uncertainties and residual distributions for each cluster. To illustrate the potential of our approach, we use a particle swarm optimization (PSO) algorithm to obtain an ensemble of 2D layer-based resistivity models from a synthetic data example and a field data set collected in Loon-Plage, France. Our strategy performs well for both synthetic and field data and allows us to extract different plausible model scenarios with their associated uncertainties and data residual distributions. Although we demonstrate our workflow using 2D ERT data and a PSObased inversion approach, the proposed strategy is general and can be adapted to analyze model ensembles generated from other kinds of geophysical data and using different global inversion approaches.
KW  - Near-surface geophysics
KW  - Electrical resistivity tomography
KW  - Non-uniqueness
KW  - Global inversion
KW  - Particle swarm optimization
KW  - Ensemble
KW  - analysis
Y1  - 2021
U6  - https://doi.org/10.1016/j.jappgeo.2021.104512
SN  - 0926-9851
SN  - 1879-1859
VL  - 196
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Arcay, Diane
A1  - Doin, Marie Pierre
A1  - Tric, Emmanuel
A1  - Bousquet, Romain
A1  - de Capitani, Christian
T1  - Overriding plate thinning in subduction zones : localized convection induced by slab dehydration
N2  - In subduction zones, many observations indicate that the backarc thermal state is particularly hot and that the upper lithosphere is thin, even if no recent extension episode has occurred. This might result from free thermal convection favored by low viscosities in the hydrated mantle wedge. We perform 2-D numerical experiments of the convective mantle wedge interaction with both the downgoing slab and the overriding plate to test this hypothesis, explore its physical mechanism, and assess its dependencies on some relevant rock properties. Water transfers across the subducting plate and the mantle wedge are explicitly modeled by including in the calculation realistic hydration/ dehydration reaction boundaries for a water-saturated mantle and oceanic crust. The rheology is non-Newtonian and temperature-, pressure-, and water content-dependent. For low strength reduction associated to water content, the upper plate is locally thinned by an enhanced corner flow. For larger strength reductions, small convection cells rapidly thin the upper plate ( in less than 15 Myr) over the area in the overriding lithosphere hydrated by slab-derived water fluxes. As a result, the thinned region location depends on the subducting plate thermal state, and it increases with high convergence rates and low subduction dip angles. Other simulations are performed to test the sole effect of hydrous rock weakening on the upper plate/mantle convective interaction. They show that the thinning process is not influenced by the corner flow, but develops at the favor of a decoupling level induced by the formation of hydroxylated minerals inside the hydrated lithosphere. The erosion mechanism identified in these simulations allows us to explain the characteristic duration of erosion as a function of the hydrous strength reduction. We find that the presence of amphibole in the upper lithosphere in significant proportions is required down to a temperature of about 980 degrees C, corresponding to an initial depth of similar to 70 km, to strongly decrease the strength of the base of the lithosphere and trigger a rapid erosion (< 15 Myr).
Y1  - 2006
UR  - http://g-cubed.org/
U6  - https://doi.org/10.1029/2005gc001061
SN  - 1525-2027
ER  - 
TY  - JOUR
A1  - Ariagno, Coline
A1  - Le Bouteiller, Caroline
A1  - van der Beek, Pieter A.
A1  - Klotz, Sébastien
T1  - Sediment export in marly badland catchments modulated by frost-cracking intensity, Draix–Bléone Critical Zone Observatory, SE France
JF  - Earth surface dynamics : ESURF ; an interactive open access journal of the European Geosciences Union
N2  - At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate, and life and can be directly monitored. Long data records (30 consecutive years for sediment yields) collected in the sparsely vegetated, steep, and small marly badland catchments of the Draix-Bleone Critical Zone Observatory (CZO), SE France, allow analyzing potential climatic controls on regolith dynamics and sediment export. Although widely accepted as a first-order control, rainfall variability does not fully explain the observed interannual variability in sediment export. Previous studies in this area have suggested that frost-weathering processes could drive regolith production and potentially modulate the observed pattern of sediment export. Here, we define sediment export anomalies as the residuals from a predictive model with annual rainfall intensity above a threshold as the control. We then use continuous soil temperature data recorded at different locations over multiple years to highlight the role of different frost-weathering processes (i.e., ice segregation versus volumetric expansion) in regolith production. Several proxies for different frost-weathering processes have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our results suggest that frost-cracking intensity (linked to ice segregation) can explain about half (47 %-64 %) of the sediment export anomalies. In contrast, the number of freeze-thaw cycles (linked to volumetric expansion) has only a minor impact on catchment sediment response. The time spent below 0 degrees C also correlates well with the sediment export anomalies and requires fewer field data to be calculated than the frost-cracking intensity. Thus, frost-weathering processes modulate sediment export by controlling regolith production in these catchments and should be taken into account when building predictive models of sediment export from these badlands under a changing climate.
Y1  - 2022
U6  - https://doi.org/10.5194/esurf-10-81-2022
SN  - 2196-6311
SN  - 2196-632X
VL  - 10
IS  - 1
SP  - 81
EP  - 96
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Armbruster, Thomas
A1  - Bermance, V.
A1  - Zebec, M.
A1  - Oberhänsli, Roland
T1  - Titanium and iron poor zincohögbomite-16H, Zn14(al,Fe3+,Ti,Mg)8Al24O62(OH)2, from Nezilovo, Macedonia: occurrence and crystal structure of a new polysome
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Armstrong, Michael R.
A1  - Radousky, Harry B.
A1  - Austin, Ryan A.
A1  - Tschauner, Oliver
A1  - Brown, Shaughnessy
A1  - Gleason, Arianna E.
A1  - Goldman, Nir
A1  - Granados, Eduardo
A1  - Grivickas, Paulius
A1  - Holtgrewe, Nicholas
A1  - Kroonblawd, Matthew P.
A1  - Lee, Hae Ja
A1  - Lobanov, Sergey
A1  - Nagler, Bob
A1  - Nam, Inhyuk
A1  - Prakapenka, Vitali
A1  - Prescher, Clemens
A1  - Reed, Evan J.
A1  - Stavrou, Elissaios
A1  - Walter, Peter
A1  - Goncharov, Alexander F.
A1  - Belof, Jonathan L.
T1  - Highly ordered graphite (HOPG) to hexagonal diamond (lonsdaleite) phase transition observed on picosecond time scales using ultrafast x-ray diffraction
JF  - Journal of applied physics
N2  - The response of rapidly compressed highly oriented pyrolytic graphite (HOPG) normal to its basal plane was investigated at a pressure of & SIM;80 GPa. Ultrafast x-ray diffraction using & SIM;100 fs pulses at the Materials Under Extreme Conditions sector of the Linac Coherent Light Source was used to probe the changes in crystal structure resulting from picosecond timescale compression at laser drive energies ranging from 2.5 to 250 mJ. A phase transformation from HOPG to a highly textured hexagonal diamond structure is observed at the highest energy, followed by relaxation to a still highly oriented, but distorted graphite structure following release. We observe the formation of a highly oriented lonsdaleite within 20 ps, subsequent to compression. This suggests that a diffusionless martensitic mechanism may play a fundamental role in phase transition, as speculated in an early work on this system, and more recent static studies of diamonds formed in impact events. Published by AIP Publishing.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0085297
SN  - 0021-8979
SN  - 1089-7550
VL  - 132
IS  - 5
PB  - AIP Publishing
CY  - Melville
ER  - 
TY  - JOUR
A1  - Arnous, Ahmad
A1  - Zeckra, Martin
A1  - Venerdini, Agostina
A1  - Alvarado, Patricia
A1  - Arrowsmith, Ramón
A1  - Guillemoteau, Julien
A1  - Landgraf, Angela
A1  - Gutiérrez, Adolfo Antonio
A1  - Strecker, Manfred
T1  - Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)
JF  - Lithosphere
N2  - Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
Y1  - 2019
U6  - https://doi.org/10.2113/2020/8888588
SN  - 1947-4253
SN  - 1941-8264
VL  - 2020
IS  - 1
SP  - 1
EP  - 25
PB  - GSA
CY  - Boulder, Colo.
ER  - 
TY  - GEN
A1  - Arnous, Ahmad
A1  - Zeckra, Martin
A1  - Venerdini, Agostina
A1  - Alvarado, Patricia
A1  - Arrowsmith, Ramón
A1  - Guillemoteau, Julien
A1  - Landgraf, Angela
A1  - Gutiérrez, Adolfo Antonio
A1  - Strecker, Manfred
T1  - Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1008 
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-480183
SN  - 1866-8372
IS  - 1008
SP  - 1
EP  - 25
ER  - 
TY  - GEN
A1  - Arodudu, Oludunsin Tunrayo
A1  - Helming, Katharina
A1  - Wiggering, Hubert
A1  - Voinov, Alexey
T1  - Bioenergy from low-intensity agricultural systems
BT  - an energy efficiency analysis
N2  - In light of possible future restrictions on the use of fossil fuel, due to climate change obligations and continuous depletion of global fossil fuel reserves, the search for alternative renewable energy sources is expected to be an issue of great concern for policy stakeholders. This study assessed the feasibility of bioenergy production under relatively low-intensity conservative, eco-agricultural settings (as opposed to those produced under high-intensity, fossil fuel based industrialized agriculture). Estimates of the net energy gain (NEG) and the energy return on energy invested (EROEI) obtained from a life cycle inventory of the energy inputs and outputs involved reveal that the energy efficiency of bioenergy produced in low-intensity eco-agricultural systems could be as much as much as 448.5–488.3 GJ·ha−1 of NEG and an EROEI of 5.4–5.9 for maize ethanol production systems, and as much as 155.0–283.9 GJ·ha−1 of NEG and an EROEI of 14.7–22.4 for maize biogas production systems. This is substantially higher than for industrialized agriculture with a NEG of 2.8–52.5 GJ·ha−1 and an EROEI of 1.2–1.7 for maize ethanol production systems, as well as a NEG of 59.3–188.7 GJ·ha−1 and an EROEI of 2.2–10.2 for maize biogas production systems. Bioenergy produced in low-intensity eco-agricultural systems could therefore be an important source of energy with immense net benefits for local and regional end-users, provided a more efficient use of the co-products is ensured.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 351 
KW  - bioenergy
KW  - biofuel
KW  - energy efficiency
KW  - NEG
KW  - EROEI
KW  - high-intensity industrialized agricultural production systems
KW  - low-intensity eco-agricultural production systems
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400403
ER  - 
TY  - JOUR
A1  - Arrowsmith, J. Ramon
A1  - Crosby, Christopher J.
A1  - Korzhenkov, Andrey M.
A1  - Mamyrov, Ernest
A1  - Povolotskaya, Irina
A1  - Guralnik, Benny
A1  - Landgraf, Angela
T1  - Surface rupture of the 1911 Kebin (Chon-Kemin) earthquake, Northern Tien Shan, Kyrgyzstan
JF  - Seismicity, fault rupture and earthquake hazards in slowly deforming regions
N2  - The 1911 Chon-Kemin (Kebin) earthquake culminated c. 30 years of remarkable earthquakes in the northern Tien Shan (Kyrgyzstan and Kazakhstan). Building on prior mapping of the event, we traced its rupture in the field and measured more than 50 offset landforms. Cumulative fault rupture length is >155-195 km along 13 fault patches comprising six sections. The patches are separated by changes of dip magnitude or dip direction, or by 4-10 km-wide stepovers. One <40 km section overlaps and is parallel to the main north-dipping rupture but is 7 km north and dips opposite (south). Both ends of the rupture are along mountain front thrust faults demonstrating late Quaternary activity. We computed the moment from each fault patch using the surface fault traces, dip inferred from the traces, 20 km seismogenic thickness, rigidity of 3.3 x 10(10) N m(-2) and dip slip converted from our observations of the largely reverse sense of motion vertical offsets. The discontinuous patches with c. 3-4 m average slip and peak slip of <14 m yield a seismic moment of 4.6 x 10(20) Nm (M-w 7.78) to 7.4 x 10(20) Nm (M-w 7.91). The majority of moment was released along the inner eastern rupture segments. This geological moment is lower by a factor of 1.5 from that determined from teleseismic data.
Y1  - 2016
SN  - 978-1-86239-745-3
SN  - 978-1-86239-964-8
U6  - https://doi.org/10.1144/SP432.10
SN  - 0305-8719
VL  - 432
SP  - 233
EP  - 253
PB  - The Geological Society
CY  - London
ER  - 
TY  - JOUR
A1  - Arrowsmith, J. Ramón
A1  - Strecker, Manfred
T1  - Seismotectonic range-front segmentation and mountain-belt growth in the Pamir-Alai region, Kyrgyzstan (India- Eurasia collision zone)
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Asari, Seiki
A1  - Wardinski, Ingo
T1  - Interannual fluctuations of the core angular momentum inferred from geomagnetic field models
JF  - Magnetic Fields in the Solar System : Planets, Moons and Solar Wind Interactions
Y1  - 2018
SN  - 978-3-319-64292-5
SN  - 978-3-319-64291-8
U6  - https://doi.org/10.1007/978-3-319-64292-5_4
SN  - 0067-0057
VL  - 448
SP  - 111
EP  - 123
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Aseev, Nikita
A1  - Shprits, Yuri Y.
A1  - Wang, Dedong
A1  - Wygant, John
A1  - Drozdov, Alexander
A1  - Kellerman, Adam C.
A1  - Reeves, Geoffrey D.
T1  - Transport and loss of ring current electrons inside geosynchronous orbit during the 17 March 2013 storm
JF  - Journal of geophysical research : Space physics
N2  - Ring current electrons (1–100 keV) have received significant attention in recent decades, but many questions regarding their major transport and loss mechanisms remain open. In this study, we use the four‐dimensional Versatile Electron Radiation Belt code to model the enhancement of phase space density that occurred during the 17 March 2013 storm. Our model includes global convection, radial diffusion, and scattering into the Earth's atmosphere driven by whistler‐mode hiss and chorus waves. We study the sensitivity of the model to the boundary conditions, global electric field, the electric field associated with subauroral polarization streams, electron loss rates, and radial diffusion coefficients. The results of the code are almost insensitive to the model parameters above 4.5 RERE, which indicates that the general dynamics of the electrons between 4.5 RE and the geostationary orbit can be explained by global convection. We found that the major discrepancies between the model and data can stem from the inaccurate electric field model and uncertainties in lifetimes. We show that additional mechanisms that are responsible for radial transport are required to explain the dynamics of ≥40‐keV electrons, and the inclusion of the radial diffusion rates that are typically assumed in radiation belt studies leads to a better agreement with the data. The overall effect of subauroral polarization streams on the electron phase space density profiles seems to be smaller than the uncertainties in other input parameters. This study is an initial step toward understanding the dynamics of these particles inside the geostationary orbit.
KW  - ring current electrons
KW  - magnetospheric convection
KW  - ensemble modeling
KW  - inner magnetosphere
KW  - electron transport
KW  - wave-particle interactions
Y1  - 2019
U6  - https://doi.org/10.1029/2018JA026031
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 2
SP  - 915
EP  - 933
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - TDS-1 GNSS Reflectometry
BT  - Development and Validation of Forward Scattering Winds
JF  - IEEE journal of selected topics in applied earth observations and remote sensing
N2  - This study presents the development and a systematic evaluation study of GNSS reflectometry wind speeds. After establishing a wind speed retrieval algorithm, UK TechDemoSat-1 (TDS-1) derived winds, from May 2015 to July 2017, are compared to the Advanced Scatterometer (ASCAT). ERA-Interim wind fields of the European Centre for Medium-range Weather Forecasts (ECMWF) and in situ observation from Tropical Atmosphere Ocean buoy array in the Pacific are taken as reference. One-year averaged TDS-1 global winds demonstrate small differences with ECMWF in a majority of areas as well as discuss under- and overestimations. The pioneering TDS-1 winds demonstrate a root-mean-squared error (RMSE) and bias of 2.77 and -0.33 m/s, which are comparable to the RMSE and bias derived by ASCAT winds, as large as 2.31 and 0.25 m/s, respectively. Using buoys measurements as reference, RMSE and bias of 2.23 and -0.03 m/s for TDS-1 as well as 1.40 and -0.68 m/s for ASCAT are obtained. Utilizing rain microwave-infrared estimates of the Tropical Rainfall Measuring Mission, rain-affected observation of both ASCAT and TDS-1 are collected and evaluated. Although ASCAT winds show a significant performance degradation resulting in an RMSE and bias of 3.16 and 1.03 m/s, respectively, during rain condition, TDS-1 shows a more reliable performance with an RMSE and bias of 2.94 and -0.21 m/s, respectively, which indicates the promising capability of GNSS forward scattering for wind retrievals during rain. A decrease in TDS-1-derived bistatic radar cross sections during rain events, at weak winds, is also demonstrated.
KW  - Advanced scatterometer (ASCAT)
KW  - European Centre for Medium-Range Weather Forecasts (ECMWF)
KW  - GNSS forward scatterometry
KW  - GNSS reflectometry
KW  - TechDemoSat-1 (TDS-1)
KW  - wind speed
Y1  - 2018
U6  - https://doi.org/10.1109/JSTARS.2018.2873241
SN  - 1939-1404
SN  - 2151-1535
VL  - 11
IS  - 11
SP  - 4534
EP  - 4541
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - Evaluating impact of rain attenuation on space-borne GNSS reflectometry wind speeds
JF  - Remote Sensing
N2  - The novel space-borne Global Navigation Satellite System Reflectometry (GNSS-R) technique has recently shown promise in monitoring the ocean state and surface wind speed with high spatial coverage and unprecedented sampling rate. The L-band signals of GNSS are structurally able to provide a higher quality of observations from areas covered by dense clouds and under intense precipitation, compared to those signals at higher frequencies from conventional ocean scatterometers. As a result, studying the inner core of cyclones and improvement of severe weather forecasting and cyclone tracking have turned into the main objectives of GNSS-R satellite missions such as Cyclone Global Navigation Satellite System (CYGNSS). Nevertheless, the rain attenuation impact on GNSS-R wind speed products is not yet well documented. Evaluating the rain attenuation effects on this technique is significant since a small change in the GNSS-R can potentially cause a considerable bias in the resultant wind products at intense wind speeds. Based on both empirical evidence and theory, wind speed is inversely proportional to derived bistatic radar cross section with a natural logarithmic relation, which introduces high condition numbers (similar to ill-posed conditions) at the inversions to high wind speeds. This paper presents an evaluation of the rain signal attenuation impact on the bistatic radar cross section and the derived wind speed. This study is conducted simulating GNSS-R delay-Doppler maps at different rain rates and reflection geometries, considering that an empirical data analysis at extreme wind intensities and rain rates is impossible due to the insufficient number of observations from these severe conditions. Finally, the study demonstrates that at a wind speed of 30 m/s and incidence angle of 30 degrees, rain at rates of 10, 15, and 20 mm/h might cause overestimation as large as approximate to 0.65 m/s (2%), 1.00 m/s (3%), and 1.3 m/s (4%), respectively, which are still smaller than the CYGNSS required uncertainty threshold. The simulations are conducted in a pessimistic condition (severe continuous rainfall below the freezing height and over the entire glistening zone) and the bias is expected to be smaller in size in real environments.
KW  - GNSS Reflectometry
KW  - wind speed
KW  - rain effect
KW  - rain attenuation
KW  - DDM simulation
Y1  - 2019
U6  - https://doi.org/10.3390/rs11091048
SN  - 2072-4292
VL  - 11
IS  - 9
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Asgarimehr, Milad
A1  - Zavorotny, Valery
A1  - Wickert, Jens
A1  - Reich, Sebastian
T1  - Can GNSS Reflectometry Detect Precipitation Over Oceans?
JF  - Geophysical research letters
N2  - For the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS-R) observations is demonstrated. Based on the argument that the forward quasi-specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS-R measurements are not sensitive to the surface small-scale roughness generated by raindrops impinging on the ocean surface. On the contrary, this study presents an evidence that the bistatic radar cross section sigma(0) derived from TechDemoSat-1 data is reduced due to rain at weak winds, lower than approximate to 6 m/s. The decrease is as large as approximate to 0.7 dB at the wind speed of 3 m/s due to a precipitation of 0-2 mm/hr. The simulations based on the recently published scattering theory provide a plausible explanation for this phenomenon which potentially enables the GNSS-R technique to detect precipitation over oceans at low winds.
KW  - GNSS Reflectometry
KW  - rain detection
KW  - rain splash
KW  - TDS-1
KW  - ocean surface
KW  - electromagnetic scattering
Y1  - 2018
U6  - https://doi.org/10.1029/2018GL079708
SN  - 0094-8276
SN  - 1944-8007
VL  - 45
IS  - 22
SP  - 12585
EP  - 12592
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ashastina, Kseniia
A1  - Kuzmina, Svetlana
A1  - Rudaya, Natalia
A1  - Troeva, Elena I.
A1  - Schoch, Werner H.
A1  - Roemermann, Christine
A1  - Reinecke, Jennifer
A1  - Otte, Volker
A1  - Savvinov, Grigoriy
A1  - Wesche, Karsten
A1  - Kienast, Frank
T1  - Woodlands and steppes
BT  - Pleistocene vegetation in Yakutia's most continental part recorded in the Batagay permafrost sequence
JF  - Quaternary science reviews : the international multidisciplinary research and review journal
N2  - Based on fossil organism remains including plant macrofossils, charcoal, pollen, and invertebrates preserved in syngenetic deposits of the Batagay permafrost sequence in the Siberian Yana Highlands, we reconstructed the environmental history during marine isotope stages (MIS) 6 to 2. Two fossil assemblages, exceptionally rich in plant remains, allowed for a detailed description of the palaeo-vegetation during two climate extremes of the Late Pleistocene, the onset of the last glacial maximum (LGM) and the last interglacial. In addition, altogether 41 assemblages were used to outline the vegetation history since the penultimate cold stage of MIS 6. Accordingly, meadow steppes analogue to modern communities of the phytosociological order Festucetalia lenensis formed the primary vegetation during the Saalian and Weichselian cold stages. Cold-resistant tundra-steppe communities (Carici rupestris-Kobresietea bellardii) as they occur above the treeline today were, in contrast to more northern locations, mostly lacking. During the last interglacial, open coniferous woodland similar to modern larch taiga was the primary vegetation at the site. Abundant charcoal indicates wildfire events during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially by abundant Urtica dioica, suggesting that the area was an interglacial refugium for large herbivores. Meadow steppes, which formed the primary vegetation during cold stages and provided potentially suitable pastures for herbivores, were a significant constituent of the plant cover in the Yana Highlands also under the full warm stage conditions of the last interglacial. Consequently, meadow steppes occurred in the Yana Highlands during the entire investigated timespan from MIS 6 to MIS 2 documenting a remarkable environmental stability. Thus, the proportion of meadow steppe vegetation merely shifted in response to the respectively prevailing climatic conditions. Their persistence indicates low precipitation and a relatively warm growing season throughout and beyond the late Pleistocene. The studied fossil record also proves that modern steppe occurrences in the Yana Highlands did not establish as late as in the Holocene but instead are relicts of a formerly continuous steppe belt extending from Central Siberia to Northeast Yakutia during the Pleistocene. The persistence of plants and invertebrates characteristic of meadow steppe vegetation in interior Yakutia throughout the late Quaternary indicates climatic continuity and documents the suitability of this region as a refugium also for other organisms of the Pleistocene mammoth steppe including the iconic large herbivores. (C)2018 Elsevier Ltd. All rights reserved.
KW  - Palaeo-vegetation
KW  - Plant macrofossils
KW  - Invertebrates
KW  - Modern analogues
KW  - Pollen
KW  - Ground squirrel nest
KW  - Last cold stage
KW  - Eemian
KW  - Beringia
Y1  - 2018
U6  - https://doi.org/10.1016/j.quascirev.2018.07.032
SN  - 0277-3791
VL  - 196
SP  - 38
EP  - 61
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Astudillo-Sotomayor, Luis
A1  - Jara Muñoz, Julius
A1  - Melnick, Daniel
A1  - Cortés‐Aranda, Joaquín
A1  - Tassara, Andrés
A1  - Strecker, Manfred
T1  - Fast Holocene slip and localized strain along the Liquiñe-Ofqui strike-slip fault system, Chile
JF  - Scientific reports
N2  - In active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; therefore, assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments. Here, we estimate a slip rate of 18.8 +/- 2.0 mm/year over the past 9.0 +/- 0.1 ka for a single strand of the Liquirie-Ofqui Fault System, which straddles the Main Cordillera in Southern Chile. This Holocene rate accounts for similar to 82% of the trench-parallel component of oblique plate convergence and is similar to million-year estimates integrated over the entire fault system. Our results imply that strain localizes on a single fault at millennial time scale but over longer time scales strain localization is not sustained. The fast millennial slip rate in the absence of historical Mw> 6.5 earthquakes along the Liquine-Ofqui Fault System implies either a component of aseismic slip or Mw similar to 7 earthquakes involving multi-trace ruptures and > 150-year repeat times. Our results have implications for the understanding of strike-slip fault system dynamics within volcanic arcs and seismic hazard assessments.
KW  - Geodynamics
KW  - Geomorphology
KW  - Tectonics
Y1  - 2021
U6  - https://doi.org/10.1038/s41598-021-85036-5
SN  - 2045-2322
VL  - 11
IS  - 1
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - London
ER  - 
TY  - GEN
A1  - Atmani, Farid
A1  - Bookhagen, Bodo
A1  - Smith, Taylor
T1  - Measuring Vegetation Heights and Their Seasonal Changes in the Western Namibian Savanna Using Spaceborne Lidars
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) with its land and vegetation height data product (ATL08), and Global Ecosystem Dynamics Investigation (GEDI) with its terrain elevation and height metrics data product (GEDI Level 2A) missions have great potential to globally map ground and canopy heights. Canopy height is a key factor in estimating above-ground biomass and its seasonal changes; these satellite missions can also improve estimated above-ground carbon stocks. This study presents a novel Sparse Vegetation Detection Algorithm (SVDA) which uses ICESat-2 (ATL03, geolocated photons) data to map tree and vegetation heights in a sparsely vegetated savanna ecosystem. The SVDA consists of three main steps: First, noise photons are filtered using the signal confidence flag from ATL03 data and local point statistics. Second, we classify ground photons based on photon height percentiles. Third, tree and grass photons are classified based on the number of neighbors. We validated tree heights with field measurements (n = 55), finding a root-mean-square error (RMSE) of 1.82 m using SVDA, GEDI Level 2A (Geolocated Elevation and Height Metrics product): 1.33 m, and ATL08: 5.59 m. Our results indicate that the SVDA is effective in identifying canopy photons in savanna ecosystems, where ATL08 performs poorly. We further identify seasonal vegetation height changes with an emphasis on vegetation below 3 m; widespread height changes in this class from two wet-dry cycles show maximum seasonal changes of 1 m, possibly related to seasonal grass-height differences. Our study shows the difficulties of vegetation measurements in savanna ecosystems but provides the first estimates of seasonal biomass changes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1275 
KW  - ICESat-2
KW  - GEDI
KW  - canopy height
KW  - lidar
KW  - savanna
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-569915
SN  - 1866-8372
IS  - 1275
ER  - 
TY  - JOUR
A1  - Atmani, Farid
A1  - Bookhagen, Bodo
A1  - Smith, Taylor
T1  - Measuring vegetation heights and their seasonal changes in the Western Namibian Savanna using spaceborne lidars
JF  - Remote sensing / Molecular Diversity Preservation International (MDPI)
N2  - The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) with its land and vegetation height data product (ATL08), and Global Ecosystem Dynamics Investigation (GEDI) with its terrain elevation and height metrics data product (GEDI Level 2A) missions have great potential to globally map ground and canopy heights. Canopy height is a key factor in estimating above-ground biomass and its seasonal changes; these satellite missions can also improve estimated above-ground carbon stocks. This study presents a novel Sparse Vegetation Detection Algorithm (SVDA) which uses ICESat-2 (ATL03, geolocated photons) data to map tree and vegetation heights in a sparsely vegetated savanna ecosystem. The SVDA consists of three main steps: First, noise photons are filtered using the signal confidence flag from ATL03 data and local point statistics. Second, we classify ground photons based on photon height percentiles. Third, tree and grass photons are classified based on the number of neighbors. We validated tree heights with field measurements (n = 55), finding a root-mean-square error (RMSE) of 1.82 m using SVDA, GEDI Level 2A (Geolocated Elevation and Height Metrics product): 1.33 m, and ATL08: 5.59 m. Our results indicate that the SVDA is effective in identifying canopy photons in savanna ecosystems, where ATL08 performs poorly. We further identify seasonal vegetation height changes with an emphasis on vegetation below 3 m; widespread height changes in this class from two wet-dry cycles show maximum seasonal changes of 1 m, possibly related to seasonal grass-height differences. Our study shows the difficulties of vegetation measurements in savanna ecosystems but provides the first estimates of seasonal biomass changes.
KW  - ICESat-2
KW  - GEDI
KW  - canopy height
KW  - lidar
KW  - savanna
Y1  - 2022
U6  - https://doi.org/10.3390/rs14122928
SN  - 2072-4292
VL  - 14
IS  - 12
SP  - 1
EP  - 20
PB  - MDPI
CY  - Basel, Schweiz
ET  - 12
ER  - 
TY  - JOUR
A1  - Atsawawaranunt, Kamolphat
A1  - Comas-Bru, Laia
A1  - Mozhdehi, Sahar Amirnezhad
A1  - Deininger, Michael
A1  - Harrison, Sandy P.
A1  - Baker, Andy
A1  - Boyd, Meighan
A1  - Kaushal, Nikita
A1  - Ahmad, Syed Masood
A1  - Brahim, Yassine Ait
A1  - Arienzo, Monica
A1  - Bajo, Petra
A1  - Braun, Kerstin
A1  - Burstyn, Yuval
A1  - Chawchai, Sakonvan
A1  - Duan, Wuhui
A1  - Hatvani, Istvan Gabor
A1  - Hu, Jun
A1  - Kern, Zoltan
A1  - Labuhn, Inga
A1  - Lachniet, Matthew
A1  - Lechleitner, Franziska A.
A1  - Lorrey, Andrew
A1  - Perez-Mejias, Carlos
A1  - Pickering, Robyn
A1  - Scroxton, Nick
A1  - Atkinson, Tim
A1  - Ayalon, Avner
A1  - Baldini, James
A1  - Bar-Matthews, Miriam
A1  - Pablo Bernal, Juan
A1  - Breitenbach, Sebastian Franz Martin
A1  - Boch, Ronny
A1  - Borsato, Andrea
A1  - Cai, Yanjun
A1  - Carolin, Stacy
A1  - Cheng, Hai
A1  - Columbu, Andrea
A1  - Couchoud, Isabelle
A1  - Cruz, Francisco
A1  - Demeny, Attila
A1  - Dominguez-Villar, David
A1  - Dragusin, Virgil
A1  - Drysdale, Russell
A1  - Ersek, Vasile
A1  - Finne, Martin
A1  - Fleitmann, Dominik
A1  - Fohlmeister, Jens Bernd
A1  - Frappier, Amy
A1  - Genty, Dominique
A1  - Holzkamper, Steffen
A1  - Hopley, Philip
A1  - Kathayat, Gayatri
A1  - Keenan-Jones, Duncan
A1  - Koltai, Gabriella
A1  - Luetscher, Marc
A1  - Li, Ting-Yong
A1  - Lone, Mahjoor Ahmad
A1  - Markowska, Monika
A1  - Mattey, Dave
A1  - McDermott, Frank
A1  - Moreno, Ana
A1  - Moseley, Gina
A1  - Nehme, Carole
A1  - Novello, Valdir F.
A1  - Psomiadis, David
A1  - Rehfeld, Kira
A1  - Ruan, Jiaoyang
A1  - Sekhon, Natasha
A1  - Sha, Lijuan
A1  - Sholz, Denis
A1  - Shopov, Yavor
A1  - Smith, Andrew
A1  - Strikis, Nicolas
A1  - Treble, Pauline
A1  - Unal-Imer, Ezgi
A1  - Vaks, Anton
A1  - Vansteenberge, Stef
A1  - Veiga-Pires, Cristina
A1  - Voarintsoa, Ny Riavo
A1  - Wang, Xianfeng
A1  - Wong, Corinne
A1  - Wortham, Barbara
A1  - Wurtzel, Jennifer
A1  - Zong, Baoyun
T1  - The SISAL database
BT  - a global resource to document oxygen and carbon isotope records from speleothems
JF  - Earth System Science Data
N2  - Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide "out-of-sample" evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (delta O-18, delta C-13) measurements are referenced by distance from the top or bottom of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information on the full range of measurements carried out on each speleothem and information on the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.
Y1  - 2018
U6  - https://doi.org/10.5194/essd-10-1687-2018
SN  - 1866-3508
SN  - 1866-3516
VL  - 10
IS  - 3
SP  - 1687
EP  - 1713
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Awais, Muhammad
A1  - Ahmad, Rafiq
A1  - Khan, Nadeem
A1  - Garapati, Prashanth
A1  - Shahzad, Muhammad
A1  - Afroz, Amber
A1  - Rashid, Umer
A1  - Khan, Sabaz Ali
T1  - Transformation of tomato variety rio grande with drought resistant transcription factor gene ATAF1 and its molecular analysis
JF  - Pakistan Journal of Botany
N2  - Tomato (Solanum lycopersicum L.) being an important vegetable is cultivated and used throughout the world. It not only contributes in fulfilling the basic nutritional requirements of the human body but also has many health benefits due to its rich biochemical composition. However, its production at large scale is hampered by many limiting factors such as biotic and abiotic stresses. Among the different abiotic stresses, drought poses drastic impact on tomato yield. Drought stress is genetically regulated by many transcription factors that not only regulate the stress responsive mechanism but also facilitate the growth and development of tomato plants. NAC is an important stress related transcription factor genes family, and the ATAF1 gene, a member of this family, is involved in ABA signaling and stress response. In this study, tomato variety Rio Drande was transformed with drought resistant ATAF1 gene via Agrobacterium mediated gene transformation method. The ATAF1 gene was first cloned in the pK7WFG2 vector having kanamycin selectable marker and then it was introduced in the Agrobacterium tumefaciens strain GV3101 through heat shock method. The tomato cotyledon and hypocotyl ex-plants of variety "Rio Ggrande" were cultured on callus induction medium (MS + 2.5 mg/L IAA + 2 mg/L BAP). The calli were then infected with Agrobacterium tumefaciens strain GV3101 containing ATAF1 gene and selection was carried out on the kanamycin selectable medium (MS + 100 mg/L Kan), and were regenerated on MS medium with 1 mg/L IAA + 1 mg/L BAP. Out of 216 putative transformed calli, 13 calli were able to regenerate on the selection medium. Of the 13 calli, three transgenic tomato plantlets were recovered, and these were confirmed through PCR analysis for the presence of 432 bp fragment of ATAF1 gene. The transformation protocol reported here can be used to generate drought resistant tomato plants in future.
KW  - Agrobacterium tumefaciens
KW  - drought stress
KW  - NAC transcription factor ATAF1
KW  - plant transformation
KW  - Rio Grande
KW  - tomato
Y1  - 2018
SN  - 0556-3321
SN  - 2070-3368
VL  - 50
IS  - 5
SP  - 1811
EP  - 1820
PB  - Pakistan botanic soc
CY  - Karachi
ER  - 
TY  - THES
A1  - Aygül, Mesut
T1  - Pre-collisional accretion and exhumation along the southern Laurasian active margin, Central Pontides, Turkey
T1  - Prä-Kollisions Akkretion und Exhumierung entlang des aktiven südlichen Kontinentalrands Laurassisens, mittlere Pontiden, Türkei
N2  - The Central Pontides is an accretionary-type orogenic area within the Alpine-Himalayan orogenic belt characterized by pre-collisional tectonic continental growth. The region comprises Mesozoic subduction-accretionary complexes and an accreted intra-oceanic arc that are sandwiched between the Laurasian active continental margin and Gondwana-derived the Kırşehir Block. The subduction-accretion complexes mainly consist of an Albian-Turonian accretionary wedge representing the Laurasian active continental margin. To the north, the wedge consists of slate/phyllite and metasandstone intercalation with recrystallized limestone, Na-amphibole-bearing metabasite (PT= 7–12 kbar and 400 ± 70 ºC) and tectonic slices of serpentinite representing accreted distal part of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed. Raman spectra of carbonaceous material (RSCM) of the metapelitic rocks revealed that the metaflysch sequence consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330 °C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. The rest are phyllites that are characterized by slightly pronounced G band with D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 °C. The phyllites are associated with a strip of incipient blueschist facies metabasites which are found as slivers within the offscraped distal turbidites. They possibly represent underplated continental metasediments together with oceanic crustal basalt along the basal décollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge. 40Ar/39Ar phengite ages from the phyllites are ca. 100 Ma, indicating Albian subduction and regional HP metamorphism.
The accreted continental metasediments are underlain by HP/LT metamorphic rocks of oceanic origin along an extensional shear zone. The oceanic metamorphic sequence mainly comprises tectonically thickened deep-seated eclogite to blueschist facies metabasites and micaschists. In the studied area, metabasites are epidote-blueschists locally with garnet (PT= 17 ± 1 kbar and 500 ± 40 °C). Lawsonite-blueschists are exposed as blocks along the extensional shear zone (PT= 14 ± 2 kbar and 370–440 °C). They are possibly associated with low shear stress regime of the initial stage of convergence. Close to the shear zone, the footwall micaschists consist of quartz, phengite, paragonite, chlorite, rutile with syn-kinematic albite porphyroblast formed by pervasive shearing during exhumation. These types of micaschists are tourmaline-bearing and their retrograde nature suggests high-fluid flux along shear zones. Peak metamorphic mineral assemblages are partly preserved in the chloritoid-micaschist farther away from the shear zone representing the zero strain domains during exhumation. Three peak metamorphic assemblages are identified and their PT conditions are constrained by pseudosections produced by Theriak-Domino and by Raman spectra of carbonaceous material: 1) garnet-chloritoid-glaucophane with lawsonite pseudomorphs (P= 17.5 ± 1 kbar, T: 390-450 °C)  2) chloritoid with glaucophane pseudomorphs (P= 16-18 kbar, T: 475 ± 40 °C) and 3) relatively high-Mg chloritoid (17%) with jadeite pseudomorphs (P= 22-25 kbar; T: 440 ± 30 °C)  in addition to phengite, paragonite, quartz, chlorite, rutile and apatite. The last mineral assemblage is interpreted as transformation of the chloritoid + glaucophane assemblage to chloritoid + jadeite paragenesis with increasing pressure. Absence of tourmaline suggests that the chloritoid-micaschist did not interact with B-rich fluids during zero strain exhumation. 40Ar/39Ar phengite age of a pervasively sheared footwall micaschist is constrained to 100.6 ± 1.3 Ma and that of a chloritoid-micaschist is constrained to 91.8 ± 1.8 Ma suggesting exhumation during on-going subduction with a southward younging of the basal accretion and the regional metamorphism. To the south, accretionary wedge consists of blueschist and greenschist facies metabasite, marble and volcanogenic metasediment intercalation. 40Ar/39Ar phengite dating reveals that this part of the wedge is of Middle Jurassic age partly overprinted during the Albian. Emplacement of the Middle Jurassic subduction-accretion complexes is possibly associated with obliquity of the Albian convergence.
Peak metamorphic assemblages and PT estimates of the deep-seated oceanic metamorphic sequence suggest tectonic stacking within wedge with different depths of burial. Coupling and exhumation of the distinct metamorphic slices are controlled by decompression of the wedge possibly along a retreating slab. Structurally, decompression of the wedge is evident by an extensional shear zone and the footwall micaschists with syn-kinematic albite porphyroblasts. Post-kinematic garnets with increasing grossular content and pseudomorphing minerals within the chloritoid-micaschists also support decompression model without an extra heating.
Thickening of subduction-accretionary complexes is attributed to i) significant amount of clastic sediment supply from the overriding continental domain and ii) deep level basal underplating by propagation of the décollement along a retreating slab. Underplating by basal décollement propagation and subsequent exhumation of the deep-seated subduction-accretion complexes are connected and controlled by slab rollback creating a necessary space for progressive basal accretion along the plate interface and extension of the wedge above for exhumation of the tectonically thickened metamorphic sequences. This might be the most common mechanism of the tectonic thickening and subsequent exhumation of deep-seated HP/LT subduction-accretion complexes.
To the south, the Albian-Turonian accretionary wedge structurally overlies a low-grade volcanic arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed north of the İzmir-Ankara-Erzincan suture (İAES), separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metavolcanic rocks are stratigraphically overlain by recrystallized micritic limestone with rare volcanogenic metaclastic rocks. Two groups can be identified based on trace and rare earth element characteristics. The first group consists of basaltic andesite/andesite (BA1) and rhyolite with abundant cognate gabbroic xenoliths. It is characterized by relative enrichment of LREE with respect to HREE. The rocks are enriched in fluid mobile LILE, and strongly depleted in Ti and P reflecting fractionation of Fe-Ti oxides and apatite, which are found in the mafic cognate xenoliths. Abundant cognate gabbroic xenoliths and identical trace and rare earth elements compositions suggest that rhyolites and basaltic andesites/andesites (BA1) are cogenetic and felsic rocks were derived from a common mafic parental magma by fractional crystallization and accumulation processes. The second group consists only of basaltic andesites (BA2) with flat REE pattern resembling island arc tholeiites. Although enriched in LILE, this group is not depleted in Ti or P.
Geochemistry of the metavolcanic rocks indicates supra-subduction volcanism evidenced by depletion of HFSE and enrichment of LILE. The arc sequence is sandwiched between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic mélange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kösdağ Arc was intra-oceanic. This is in accordance with basaltic andesites (BA2) with island arc tholeiite REE pattern.
Zircons from two metarhyolite samples give Late Cretaceous (93.8 ± 1.9 and 94.4 ± 1.9 Ma) U/Pb ages. Low-grade regional metamorphism of the intra-oceanic arc sequence is constrained 69.9 ± 0.4 Ma by 40Ar/39Ar dating on metamorphic muscovite from a metarhyolite indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. The youngest 40Ar/39Ar phengite age from the overlying subduction-accretion complexes is 92 Ma confirming southward younging of an accretionary-type orogenic belt. Hence, the arc sequence represents an intra-oceanic paleo-arc that formed above the sinking Tethyan slab and finally accreted to Laurasian active continental margin. Abrupt non-collisional termination of arc volcanism was possibly associated with southward migration of the arc volcanism similar to the Izu-Bonin-Mariana arc system.
The intra-oceanic Kösdağ Arc is coeval with the obducted supra-subduction ophiolites in NW Turkey suggesting that it represents part of the presumed but missing incipient intra-oceanic arc associated with the generation of the regional supra-subduction ophiolites. Remnants of a Late Cretaceous intra-oceanic paleo-arc and supra-subduction ophiolites can be traced eastward within the Alp-Himalayan orogenic belt. This reveals that Late Cretaceous intra-oceanic subduction occurred as connected event above the sinking Tethyan slab. It resulted as arc accretion to Laurasian active margin and supra-subduction ophiolite obduction on Gondwana-derived terranes.
N2  - Die Mittelpontiden sind ein akkretionäres orogenes Gebiet innerhalb des Alpen-Himalaya Orogengürtels, das durch präkollisionales tektonisches kontinentales Wachstum gekennzeichnet ist. Die Region umfasst mesozoische subduktions-akkretions Komplexe und einen akkretierten intraozeanischen Bogen, die zwischen dem aktiven laurassischen Kontinentalrand und dem von Gondwana abgeleiteten Kırşehir Block eingeklemmt sind. Die Subduktions-Akkretionskomplexe bestehen hauptsächlich aus einem Alb-Turon Akkretionskeil, der den aktiven laurassischen Kontinentalrand repräsentiert. Im Norden besteht der Keil aus Schiefer/Phyllit und Metasandsteineinlagerungen mit rekristallisiertem Kalkstein, Na-Amphibole-tragendem Metabasit (PT= 7-12 kbar und 400 ± 70 ºC) und tektonischen Serpentinit-Einlagerungen, die einen distalen Teil eines großen submarinen Turbiditfächers der Unterkreide darstellen, der auf dem aktiven Kontinentalrand von Lauras abgelagert und anschließend akkretiert und metamorphisiert wurde. Ramanspektren von kohlenstoffhaltigem Material (RSCM) der metapelitischen Gesteine zeigen, dass die Metaflyschsequenz aus metamorphen Paketen mit ausgeprägten metamorphen Temperaturspitzen besteht. Die Mehrheit der Metapelite sind Niedertemperatur (ca. 330 °C) Schiefer, die sich durch eine mangelnde Differenzierung der Defektbänder Graphit (G) und D2 auszeichnen. Sie stellen möglicherweise abgetragene distale Turbidite entlang der Sohle des Akkretionskeils im Alb dar. Der Rest sind Phyllite, die sich durch ein leicht ausgeprägtes G-Band mit D2-Defektband an der Schulter auszeichnen. Die metamorphen Temperaturen dieser Phyllite sind auf 370-385 °C begrenzt. Die Phyllite sind mit Streifen von Metabasiten der beginnenden blauen Fazies assoziiert, die sich als Bänder innerhalb der abgetragenen distalen Turbidite befinden. Sie stellen möglicherweise unterschichtete kontinentale Metasedimente zusammen mit ozeanischem Krustenbasalt entlang des basalen Decollements dar. Die tektonische Einlagerung der unterschobenen Gesteine in die abgetragenen distalen Turbidite wurde möglicherweise durch "out-of-sequence thrusting" erreicht, was zu einer tektonischen Verdickung und Hebung des Keils führte. 40Ar/39Ar Phengit Alter von den Phylliten sind ca. 100 Ma, was auf  Subduktion und regionale HP-Metamorphose während dem Alb hinweist.

Die akkretierten kontinentalen Metasedimente werden von HP/LT-metamorphen Gesteinen ozeanischen Ursprungs entlang einer ausgedehnten Scherzone durchzogen. Die ozeanisch metamorphe Sequenz umfasst hauptsächlich tektonisch verdickte, tief sitzende Eklogite bis hin zu blauschieferfaziellen Metabasiten und Glimmerschiefern. Im Untersuchungsgebiet treten Metabasite als Epidot-Blauschiefer lokal mit Granat auf (PT= 17 ± 1 kbar und 500 ± 40 °C). Lawsonit-Blauschiefer treten als Blöcke entlang einer Extensionsscherzone auf (PT= 14 ± 2 kbar und 370-440 °C). Sie sind möglicherweise mit einem niedrigen Scherspannungsregime während der Anfangsphase der Konvergenz verbunden. In der Nähe der Scherzone bestehen die Glimmerschiefer aus Quarz, Phengit, Paragonit, Chlorit, Rutil und syn-kinematischen Albitporphyroblasten, die durch Scherung während der Exhumierung entstanden. Die Glimmerschiefer führen Turmalin und ihre retrograde Natur deutet auf hohen Fluidflux entlang der Scherzonen. Mineralvergesellschaftungen des metamorphen Maximums sind, weiter weg von der Scherzone, teilweise noch in den Chloritoid-Glimmerschiefern erhalten.  Diese Domänen erfuhren während der Exhumierung keinen Strain. Drei metamorphe Vergesellschaftungen wurden identifiziert und ihre PT-Bedingungen durch  Theriak-Domino Modellierung und  Raman-Spektren von kohlenstoffhaltigem Material eingeschränkt: 1) Granat-Chloritoid-Glaukophan mit Lawsonit-Pseudomorphen (P= 17.5 ± 1 kbar, T: 390-450 °C); 2) Chloritoid mit Glaukophan-Pseudomorphen (P= 16-18 kbar, T: 475 ± 40 °C) und 3) relativ hoch-Mg-Chloritoid (17%) mit Jadeit-Pseudomorphen (P= 22-25 kbar; T: 440 ± 30 °C) zusätzlich zu Phengit, Paragonit, Quarz, Chlorit, Rutil und Apatit. Die letzte Mineralparagenese  wird interpretiert als Transformation der Chloritoid + Glaukophan Vergesellschaftung zu Chloritoid + Jadeit Paragenese mit steigendem Druck. Das Fehlen von Turmalin deutet darauf hin, dass der Chloritoid-Glimmerschiefer während der strain-freien Exhumierung nicht mit B-reichen Fluiden reagiert hat. Das 40Ar/39Ar Phengitalter eines penetrativ geschieferten Glimmerschiefers ist auf 100,6 ± 1,3 Ma und das eines Chlorit-Glimmerschiefers auf 91,8 ± 1,8 Ma begrenzt, was auf eine Exhumierung während der laufenden Subduktion mit einer südlichen Verjüngung der Basalakkretion und des regionalen Metamorphismus hindeutet. Im Süden besteht der Akkretionskeil aus blauschiefer- und grünschieferfaziellen Metabasiten, Marmoren und vulkanogenen Metasedimenteinlagerungen. 40Ar/39Ar Phengit Datierung zeigt, dass dieser Teil des Keils aus dem Mittleren Jura stammt, der während des Albs teilweise überprägt wurde. Die Platznahe der Subduktions-/Akkretionskomplexe des Mittleren Jura ist möglicherweise mit einer schiefen Lage der Konvergenz im Alb verbunden.

Peak metamorphe Mineralvergesellschaftungen und PT-Schätzungen der tiefliegenden ozeanischen metamorphen Sequenz deuten auf eine tektonische Stapelung im Akkretionskeil mit unterschiedlichen Grabentiefen hin. Die Kopplung und Exhumierung der einzelnen metamorphen Einheiten wird durch Dekompression des Keils gesteuert, möglicherweise entlang einer sich zurückziehenden Platte. Strukturell ist die Dekompression des Keils durch eine ausgedehnte Scherzone und die Glimmerschiefer der Basis mit syn-kinematischen Albitporphyroblasten erkennbar. Postkinematische Granate mit steigendem Grossulargehalt und pseudomorphe Mineralien innerhalb der Chloritoid-Glimmerschiefer unterstützen ein Dekompressionsmodell ohne zusätzliche Erwärmung.

Die Verdickung der Subduktions-/Akkretionskomplexe wird zugeschrieben: i) einer signifikanten Menge an klastischer Sedimentzufuhr aus dem überschobenen kontinentalen Bereich und ii) tiefer basaler Unterschiebung durch Ausbreitung des Decollements entlang einer sich zurückziehenden Platte. Die Unterschiebung durch basale Decollementausbreitung und anschließende Exhumierung der tief liegenden Subduktions-Akkretionskomplexe wird durch Slab-Rollback gesteuert. Dadurch wird der notwendige Raum für eine progressive basale Akkretion entlang der Plattengrenze und der Verlängerung des überliegenden Keils  für die Exhumierung der tektonisch verdickten metamorphen Sequenzen geschaffen. Dies könnte der wichtigste Mechanismus tektonischer Verdickung und anschließender Exhumierung von tief sitzenden HP/LT-Subduktions-Akkretionskomplexen sein.

Im Süden liegt der Akkretionskeil des Alb-Turon strukturell über einer  vulkanischen Bogensequenz aus niedriggradigen metavulkanischem Gestein und darüber liegender metasedimentärer Abfolge. Diese Metavulkanite, treten nördlich der  İzmir-Ankara-Erzincan Sutur (İAES), welche Laurasia von der aus Gondwana stammenden Terranen trennt. Die metavulkanischen Gesteine bestehen hauptsächlich aus basaltischem Andesit/Andesit und Rhyolith mit mafischen Xenolithen sowie mit ihren pyroklastischen Äquivalenten, welche mit rekristallisiertem pelagischem Kalkstein und Hornstein durchsetzt sind. Die metavulkanischen Gesteine sind stratigraphisch überlagert von rekristallisiertem mikritischem Kalkstein mit seltenen vulkanischen metaklastischen Gesteinen. Zwei Gruppen können anhand von Spuren- und Seltenerden-gehalten identifiziert werden. Die erste Gruppe besteht aus basaltischem Andesit/Andesit (BA1) und Rhyolith mit zahlreichen  gabbroiden Xenolithen. Sie ist  durch eine relative Anreicherung von LREE gegenüber HREE gekennzeichnet. Die Gesteine sind mit fluidmobilen LILE angereichert und stark in Ti und P abgereichert, was die Fraktionierung von Fe-Ti-Oxiden und Apatit widerspiegelt, die in den mafischen Xenolithen zu finden sind. Reichlich gabbroide Xenolithe und identische Spuren- und Seltenerdelemente-Zusammensetzungen deuten darauf hin, dass Rhyolithe und basaltische Andesite/Andesite (BA1) kogenetisch sind und die felsischen Gesteine von einem gemeinsamen mafischen Magma durch fraktionierte Kristallisations- und Akkumulationsprozesse abgeleitet wurden. Die zweite Gruppe besteht nur aus basaltischen Andesiten (BA2) mit flachem REE-Muster, das an Inselbogen-Tholeiite erinnert. Obwohl angereichert mit LILE, ist diese Gruppe nicht Ti oder P verarmt.

Die Geochemie der metavulkanischen Gesteine deutet auf Supra-Subduktionsvulkanismus hin, der durch den Abbau von HFSE und die Anreicherung von LILE belegt ist. Die Insel-Bogensequenz ist zwischen einem  subduktions-akkretionären Komplex des Alb-Turon, der den laurassischen aktiven Kontinentalrandrand repräsentiert, und einer ophiolitischen Mélange eingeklemmt. Das Fehlen von kontinentalem Detritus in der Insel-Bogensequenz und seine tektonische Anordnung in einem breiten kreidezeitlichen Akkretionskomplex deuten darauf hin, dass der Kösdağ Arc intraozeanisch war. Dem entsprechen die basaltischen Andesiten (BA2) mit Inselbogen-Tholeiit-REE-Muster.

Zirkon aus zwei Metarhyolithproben ergibt U/Pb-Alter der Spätkreide (93,8 ± 1,9 und 94,4 ± 1,9 Ma). Die niedriggradige regionale Metamorphose der intraozeanischen Bogensequenz ist durch 40Ar/39Ar Datierung von metamorphem Muskovit aus einem Metarhyolith auf 69,9 ± 0,4 Ma eingegrenzt, was darauf hindeutet, dass die Insel-Bogensequenz in der späten Kreide Teil des breiten  Akkretionskomplexes der Tethys wurde. Das jüngste Phengitalter von 40Ar/39Ar aus den darüber liegenden Subduktions-Akkretionskomplexen ist 92 Ma, was die Verjüngung des akkretionären orogenen Gürtels gegen Süden bestätigt. Die Insel-Bogensequenz stellt somit einen intraozeanischen Paläobogen dar, der sich über der absinkenden Tethys-platte gebildet und schließlich an den aktiven laurassischen Kontinentalrand akkretiert hat. Der abrupte, nicht kollisionsbedingte Abbruch des Insel-Bogenvulkanismus war möglicherweise mit der südwärts Wanderung des Vulkanismus ähnlich dem Izu-Bonin-Mariana-Bogensystem verbunden.

Der intraozeanische Kösdağ Bogen ist gleichaltrig zu den obduzierten Supra-Subduktionsophiolithen der Nordwesttürkei, was darauf hindeutet, dass er einen Teil des vermuteten, aber fehlenden beginnenden intraozeanischen Systems darstellt, das mit der Erzeugung der regionalen Supra-Subduktionsophiolithe verbunden ist. Überreste eines intraozeanischen Paläobogens und supra-subduzierter Ophiolithe der späten Kreide können innerhalb des orogenen Alpen-Himalaya-Gürtels nach Osten verfolgt werden. Dies zeigt, dass die intraozeanische Subduktion der Spätkreide als verbreitetes Ereignis über der absinkenden Platte der Tethys stattfand. Dieses führte zur Insel-Bogenakkretion am aktiven Kontinenntalrand Laurasirns und zur Supra-Subduktion Ophiolith-obduktion auf aus Gondwana stammenden Terranen.
KW  - Eurasian active margin
KW  - subduction-accretionary complexes
KW  - HP/LT metamorphism
KW  - Pontides
KW  - Eurasischer aktiver Kontinentalrand
KW  - subduktions-akkretions Komplexe
KW  - HP/LT-Metamorphose
KW  - Pontiden
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-416769
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Oberhänsli, Roland
T1  - Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab-Mantle Decoupling
JF  - Tectonics
N2  - High-pressure/low-temperature (HP/LT) chloritoid-bearing micaschists crop out widely in the central part of northern Turkey and represent deep-seated subduction-accretionary complexes. Three peak metamorphic assemblages are identified in the area studied: (1) garnet-chloritoid-glaucophane with pseudomorphs after lawsonite; (2) chloritoid with pseudomorphs after glaucophane; and (3) chloritoid with pseudomorphs after jadeite in addition to phengite, paragonite, quartz, chlorite, rutile, and apatite. The latter is interpreted as transformation of a chloritoid + glaucophane assemblage to chloritoid + jadeite with increasing pressure; PT modeling indicates similar to 17 and 22-25 kbars for the two peak parageneses. The diversity of peak metamorphic assemblages and the PT estimates suggest that basal accretion occurred at different depths within the wedge. The depth of the basal accretion is possibly controlled by the slab-mantle decoupling depth. Stretching and thinning of the lithospheric fore arc induced by the slab rollback possibly caused shallowing of the slab-mantle decoupling depth which limited depth of the basal accretion from 70-80km to similar to 55km within the subduction channel. A slab-mantle coupling depth-controlled basal accretion may also explain the scarcity of eclogite and high-grade blueschist facies metamorphic rocks in active intraoceanic subduction zones. Because the overriding plate is young and hot in intraoceanic subductions, the slab and mantle are coupled at a relatively shallow depth before eclogitization of the oceanic crust. This prevents accretion and exhumation of eclogite along the subduction channel.
KW  - chloritoid micaschist
KW  - accretionary complex
KW  - slab-mantle decoupling
KW  - basal accretion
Y1  - 2017
U6  - https://doi.org/10.1002/2017TC004689
SN  - 0278-7407
SN  - 1944-9194
VL  - 36
SP  - 2332
EP  - 2346
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Okay, Aral I.
A1  - Oberhänsli, Roland
A1  - Schmidt, Alexander
A1  - Sudo, Masafumi
T1  - Late Cretaceous infant intra-oceanic arc volcanism, the Central Pontides, Turkey: Petrogenetic and tectonic implications
JF  - Journal of Asian earth sciences
N2  - A tectonic slice of an arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed in the Central Pontides north of the Izmir-Ankara-Erzincan suture separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metasedimentary succession comprises recrystallized micritic limestone with rare volcanogenic metaclastic rocks and stratigraphically overlies the metavolcanic rocks. The geochemistry of the metavolcanic rocks indicates an arc setting evidenced by depletion of HFSE (Ti, P and Nb) and enrichment of fluid mobile LILE. Identical trace and rare earth elements compositions of basaltic andesites/andesites and rhyolites suggest that they are cogenetic and derived from a common parental magma. The arc sequence crops out between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic melange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kosdag Arc was intra-oceanic. Zircons from two metarhyolite samples give Late Cretaceous (93.8 +/- 1.9 and 94.4 +/- 1.9 Ma) U/Pb ages. These ages are the same as the age of the supra-subduction ophiolites in western Turkey, which implies that that the Kosdag Arc may represent part of the incipient arc formed during the generation of the supra-subduction ophiolites. The low-grade regional metamorphism in the Kosdag Arc is constrained to 69.9 +/- 0.4 Ma by Ar-40/Ar-39 muscovite dating indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. Non-collisional cessation of the arc volcanism is possibly associated with southward migration of the magmatism as in the Izu-Bonin-Mariana arc system. (c) 2015 Elsevier Ltd. All rights reserved.
KW  - Intra-oceanic subduction
KW  - Felsic volcanism
KW  - Arc accretion
KW  - Ophiolite obduction
Y1  - 2015
U6  - https://doi.org/10.1016/j.jseaes.2015.07.005
SN  - 1367-9120
SN  - 1878-5786
VL  - 111
SP  - 312
EP  - 327
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aygül, Mesut
A1  - Okay, Aral I.
A1  - Oberhänsli, Roland
A1  - Ziemann, Martin Andreas
T1  - Thermal structure of low-grade accreted Lower Cretaceous distal turbidites, the Central Pontides, Turkey: insights for tectonic thickening of an accretionary wedge
JF  - Turkish journal of earth sciences = Türk yerbilimleri dergisi
N2  - Albian-Turonian subduction-accretionary complexes are exposed widely in the Central Pontides. A major portion of the accretionary complexes is made up of a metaflysch sequence consisting of slate/phyllite and metasandstone intercalation with blocks of marble, Na-amphibole bearing metabasite, and serpentinite. The metaflysch sequence represents distal parts of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed during the Albian. Raman spectra of carbonaceous material of the metapelitic rocks revealed that the metaflysch consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330 degrees C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. Other phyllites are characterized by a slightly pronounced G band with a D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 degrees C. The phyllites are associated with a strip of incipient blueschist facies metabasites and are found as a sliver within the offscraped distal turbidites. We interpret the phyllites as underplated continental sediments together with oceanic crustal basalt along the basal decollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge.
KW  - Pontides
KW  - distal turbidites
KW  - offscraping
KW  - underplating
KW  - low-grade metamorphism
KW  - graphitization
KW  - Raman microspectroscopy
Y1  - 2015
U6  - https://doi.org/10.3906/yer-1504-4
SN  - 1300-0985
VL  - 24
IS  - 5
SP  - 461
EP  - 474
PB  - Tübitak
CY  - Ankara
ER  - 
TY  - JOUR
A1  - Ayllon, Daniel
A1  - Grimm, Volker
A1  - Attinger, Sabine
A1  - Hauhs, Michael
A1  - Simmer, Clemens
A1  - Vereecken, Harry
A1  - Lischeid, Gunnar
T1  - Cross-disciplinary links in environmental systems science
BT  - Current state and claimed needs identified in a meta-review of process models
JF  - The science of the total environment : an international journal for scientific research into the environment and its relationship with man
N2  - Terrestrial environmental systems are characterised by numerous feedback links between their different compartments. However, scientific research is organized into disciplines that focus on processes within the respective compartments rather than on interdisciplinary links. Major feedback mechanisms between compartments might therefore have been systematically overlooked so far. Without identifying these gaps, initiatives on future comprehensive environmental monitoring schemes and experimental platforms might fail. We performed a comprehensive overview of feedbacks between compartments currently represented in environmental sciences and explores to what degree missing links have already been acknowledged in the literature. We focused on process models as they can be regarded as repositories of scientific knowledge that compile findings of numerous single studies. In total, 118 simulation models from 23 model types were analysed. Missing processes linking different environmental compartments were identified based on a meta-review of 346 published reviews, model inter-comparison studies, and model descriptions. Eight disciplines of environmental sciences were considered and 396 linking processes were identified and ascribed to the physical, chemical or biological domain. There were significant differences between model types and scientific disciplines regarding implemented interdisciplinary links. The most wide-spread interdisciplinary links were between physical processes in meteorology, hydrology and soil science that drive or set the boundary conditions for other processes (e.g., ecological processes). In contrast, most chemical and biological processes were restricted to links within the same compartment. Integration of multiple environmental compartments and interdisciplinary knowledge was scarce in most model types. There was a strong bias of suggested future research foci and model extensions towards reinforcing existing interdisciplinary knowledge rather than to open up new interdisciplinary pathways. No clear pattern across disciplines exists with respect to suggested future research efforts. There is no evidence that environmental research would clearly converge towards more integrated approaches or towards an overarching environmental systems theory. (c) 2017 Elsevier B.V. All rights reserved.
KW  - Review
KW  - Interdisciplinary links
KW  - Integrated environmental modelling
KW  - Research needs
Y1  - 2018
U6  - https://doi.org/10.1016/j.scitotenv.2017.12.007
SN  - 0048-9697
SN  - 1879-1026
VL  - 622
SP  - 954
EP  - 973
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - GEN
A1  - Ayzel, Georgy
A1  - Izhitskiy, Alexander
ED  - Xu, Z Peng
T1  - Coupling physically based and data-driven models for assessing freshwater inflow into the Small Aral Sea
T2  - Innovative Water Resources Management in a Changing Environment – Understanding and Balancing Interactions between Humankind and Nature
N2  - The Aral Sea desiccation and related changes in hydroclimatic conditions on a regional level is a hot topic for past decades. The key problem of scientific research projects devoted to an investigation of modern Aral Sea basin hydrological regime is its discontinuous nature - the only limited amount of papers takes into account the complex runoff formation system entirely. Addressing this challenge we have developed a continuous prediction system for assessing freshwater inflow into the Small Aral Sea based on coupling stack of hydrological and data-driven models. Results show a good prediction skill and approve the possibility to develop a valuable water assessment tool which utilizes the power of classical physically based and modern machine learning models both for territories with complex water management system and strong water-related data scarcity. The source code and data of the proposed system is available on a Github page (https://github.com/SMASHIproject/IWRM2018).
Y1  - 2018
U6  - https://doi.org/10.5194/piahs-379-151-2018
SN  - 2199-899X
VL  - 379
SP  - 151
EP  - 158
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Ayzel, Georgy
A1  - Scheffer, Tobias
A1  - Heistermann, Maik
T1  - RainNet v1.0
BT  - a convolutional neural network for radar-based precipitation nowcasting
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - In this study, we present RainNet, a deep convolutional neural network for radar-based precipitation nowcasting. Its design was inspired by the U-Net and SegNet families of deep learning models, which were originally designed for binary segmentation tasks. RainNet was trained to predict continuous precipitation intensities at a lead time of 5min, using several years of quality-controlled weather radar composites provided by the German Weather Service (DWD). That data set covers Germany with a spatial domain of 900km × 900km and has a resolution of 1km in space and 5min in time. Independent verification experiments were carried out on 11 summer precipitation events from 2016 to 2017. In order to achieve a lead time of 1h, a recursive approach was implemented by using RainNet predictions at 5min lead times as model inputs for longer lead times. In the verification experiments, trivial Eulerian persistence and a conventional model based on optical flow served as benchmarks. The latter is available in the rainymotion library and had previously been shown to outperform DWD's operational nowcasting model for the same set of verification events.

RainNet significantly outperforms the benchmark models at all lead times up to 60min for the routine verification metrics mean absolute error (MAE) and the critical success index (CSI) at intensity thresholds of 0.125, 1, and 5mm h⁻¹. However, rainymotion turned out to be superior in predicting the exceedance of higher intensity thresholds (here 10 and 15mm h⁻¹). The limited ability of RainNet to predict heavy rainfall intensities is an undesirable property which we attribute to a high level of spatial smoothing introduced by the model. At a lead time of 5min, an analysis of power spectral density confirmed a significant loss of spectral power at length scales of 16km and below. Obviously, RainNet had learned an optimal level of smoothing to produce a nowcast at 5min lead time. In that sense, the loss of spectral power at small scales is informative, too, as it reflects the limits of predictability as a function of spatial scale. Beyond the lead time of 5min, however, the increasing level of smoothing is a mere artifact – an analogue to numerical diffusion – that is not a property of RainNet itself but of its recursive application. In the context of early warning, the smoothing is particularly unfavorable since pronounced features of intense precipitation tend to get lost over longer lead times. Hence, we propose several options to address this issue in prospective research, including an adjustment of the loss function for model training, model training for longer lead times, and the prediction of threshold exceedance in terms of a binary segmentation task. Furthermore, we suggest additional input data that could help to better identify situations with imminent precipitation dynamics. The model code, pretrained weights, and training data are provided in open repositories as an input for such future studies.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 964 
KW  - weather
KW  - models
KW  - skill
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-472942
SN  - 1866-8372
IS  - 964
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy
A1  - Scheffer, Tobias
A1  - Heistermann, Maik
T1  - RainNet v1.0
BT  - a convolutional neural network for radar-based precipitation nowcasting
JF  - Geoscientific Model Development
N2  - In this study, we present RainNet, a deep convolutional neural network for radar-based precipitation nowcasting. Its design was inspired by the U-Net and SegNet families of deep learning models, which were originally designed for binary segmentation tasks. RainNet was trained to predict continuous precipitation intensities at a lead time of 5min, using several years of quality-controlled weather radar composites provided by the German Weather Service (DWD). That data set covers Germany with a spatial domain of 900km × 900km and has a resolution of 1km in space and 5min in time. Independent verification experiments were carried out on 11 summer precipitation events from 2016 to 2017. In order to achieve a lead time of 1h, a recursive approach was implemented by using RainNet predictions at 5min lead times as model inputs for longer lead times. In the verification experiments, trivial Eulerian persistence and a conventional model based on optical flow served as benchmarks. The latter is available in the rainymotion library and had previously been shown to outperform DWD's operational nowcasting model for the same set of verification events.

RainNet significantly outperforms the benchmark models at all lead times up to 60min for the routine verification metrics mean absolute error (MAE) and the critical success index (CSI) at intensity thresholds of 0.125, 1, and 5mm h⁻¹. However, rainymotion turned out to be superior in predicting the exceedance of higher intensity thresholds (here 10 and 15mm h⁻¹). The limited ability of RainNet to predict heavy rainfall intensities is an undesirable property which we attribute to a high level of spatial smoothing introduced by the model. At a lead time of 5min, an analysis of power spectral density confirmed a significant loss of spectral power at length scales of 16km and below. Obviously, RainNet had learned an optimal level of smoothing to produce a nowcast at 5min lead time. In that sense, the loss of spectral power at small scales is informative, too, as it reflects the limits of predictability as a function of spatial scale. Beyond the lead time of 5min, however, the increasing level of smoothing is a mere artifact – an analogue to numerical diffusion – that is not a property of RainNet itself but of its recursive application. In the context of early warning, the smoothing is particularly unfavorable since pronounced features of intense precipitation tend to get lost over longer lead times. Hence, we propose several options to address this issue in prospective research, including an adjustment of the loss function for model training, model training for longer lead times, and the prediction of threshold exceedance in terms of a binary segmentation task. Furthermore, we suggest additional input data that could help to better identify situations with imminent precipitation dynamics. The model code, pretrained weights, and training data are provided in open repositories as an input for such future studies.
KW  - weather
KW  - models
KW  - skill
Y1  - 2020
U6  - https://doi.org/10.5194/gmd-13-2631-2020
SN  - 1991-959X
SN  - 1991-9603
VL  - 13
IS  - 6
SP  - 2631
EP  - 2644
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy V.
T1  - Runoff predictions in ungauged arctic basins using conceptual models forced by reanalysis data
JF  - Water Resources
N2  - Due to global warming, the problem of assessing water resources and their vulnerability to climate drivers in the Arctic region has become a focus in the recent years. This study is aimed at investigating three lumped hydrological models to predict daily runoff of large-scale Arctic basins in the case of substantial data scarcity. All models were driven only by meteorological forcing reanalysis dataset without any additional information about landscape, soil, or vegetation cover properties of the studied basins. Model parameter regionalization based on transferring the whole parameter set showed good efficiency for predictions in ungauged basins. We run a blind test of the proposed methodology for ensemble runoff predictions on five sub-basins, for which only monthly observations were available, and obtained promising results for current water resources assessment for a broad domain of ungauged basins in the Russian Arctic.
KW  - hydrologic modeling
KW  - runoff
KW  - ungauged basins
KW  - reanalysis
KW  - Arctic
Y1  - 2018
U6  - https://doi.org/10.1134/S0097807818060180
SN  - 0097-8078
SN  - 1608-344X
VL  - 45
SP  - S1
EP  - S7
PB  - Pleiades Publ.
CY  - New York
ER  - 
TY  - GEN
A1  - Ayzel, Georgy
A1  - Varentsova, Natalia
A1  - Erina, Oxana
A1  - Sokolov, Dmitriy
A1  - Kurochkina, Liubov
A1  - Moreydo, Vsevolod
T1  - OpenForecast
BT  - The First Open-Source Operational Runoff Forecasting System in Russia
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The development and deployment of new operational runoff forecasting systems are a strong focus of the scientific community due to the crucial importance of reliable and timely runoff predictions for early warnings of floods and flashfloods for local businesses and communities. OpenForecast, the first operational runoff forecasting system in Russia, open for public use, is presented in this study. We developed OpenForecast based only on open-source software and data-GR4J hydrological model, ERA-Interim meteorological reanalysis, and ICON deterministic short-range meteorological forecasts. Daily forecasts were generated for two basins in the European part of Russia. Simulation results showed a limited efficiency in reproducing the spring flood of 2019. Although the simulations managed to capture the timing of flood peaks, they failed in estimating flood volume. However, further implementation of the parsimonious data assimilation technique significantly alleviates simulation errors. The revealed limitations of the proposed operational runoff forecasting system provided a foundation to outline its further development and improvement.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1338 
KW  - OpenForecast
KW  - open
KW  - operational service
KW  - runoff
KW  - forecasting
KW  - Russia
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-473295
SN  - 1866-8372
IS  - 1338
ER  - 
TY  - JOUR
A1  - Ayzel, Georgy
A1  - Varentsova, Natalia
A1  - Erina, Oxana
A1  - Sokolov, Dmitriy
A1  - Kurochkina, Liubov
A1  - Moreydo, Vsevolod
T1  - OpenForecast
BT  - The First Open-Source Operational Runoff Forecasting System in Russia
JF  - Water : Molecular Diversity Preservation International
N2  - The development and deployment of new operational runoff forecasting systems are a strong focus of the scientific community due to the crucial importance of reliable and timely runoff predictions for early warnings of floods and flashfloods for local businesses and communities. OpenForecast, the first operational runoff forecasting system in Russia, open for public use, is presented in this study. We developed OpenForecast based only on open-source software and data-GR4J hydrological model, ERA-Interim meteorological reanalysis, and ICON deterministic short-range meteorological forecasts. Daily forecasts were generated for two basins in the European part of Russia. Simulation results showed a limited efficiency in reproducing the spring flood of 2019. Although the simulations managed to capture the timing of flood peaks, they failed in estimating flood volume. However, further implementation of the parsimonious data assimilation technique significantly alleviates simulation errors. The revealed limitations of the proposed operational runoff forecasting system provided a foundation to outline its further development and improvement.
KW  - OpenForecast
KW  - open
KW  - operational service
KW  - runoff
KW  - forecasting
KW  - Russia
Y1  - 2019
U6  - https://doi.org/10.3390/w11081546
SN  - 2073-4441
VL  - 11
IS  - 8
PB  - MDPI
CY  - Basel
ER  - 
TY  - THES
A1  - Bach, Christoph
T1  - Improving statistical seismicity models
T1  - Weiterentwicklung statistischer Seismizitätsmodelle
N2  - Several mechanisms are proposed to be part of the earthquake triggering process, including static stress interactions and dynamic stress transfer. Significant differences of these mechanisms are particularly expected in the spatial distribution of aftershocks. However, testing the different hypotheses is challenging because it requires the consideration of the large uncertainties involved in stress calculations as well as the appropriate consideration of secondary aftershock triggering which is related to stress changes induced by smaller pre- and aftershocks. In order to evaluate the forecast capability of different mechanisms, I take the effect of smaller--magnitude earthquakes into account by using the epidemic type aftershock sequence (ETAS) model where the spatial probability distribution of direct aftershocks, if available, is correlated to alternative source information and mechanisms. Surface shaking, rupture geometry, and slip distributions are tested. As an approximation of the shaking level, ShakeMaps are used which are available in near real-time after a mainshock and thus could be used for first-order forecasts of the spatial aftershock distribution. Alternatively, the use of empirical decay laws related to minimum fault distance is tested and Coulomb stress change calculations based on published and random slip models. For comparison, the likelihood values of the different model combinations are analyzed in the case of several well-known aftershock sequences (1992 Landers, 1999 Hector Mine, 2004 Parkfield). The tests show that the fault geometry is the most valuable information for improving aftershock forecasts. Furthermore, they reveal that static stress maps can additionally improve the forecasts of off--fault aftershock locations, while the integration of ground shaking data could not upgrade the results significantly. In the second part of this work, I focused on a procedure to test the information content of inverted slip models. This allows to quantify the information gain if this kind of data is included in aftershock forecasts. For this purpose, the ETAS model based on static stress changes, which is introduced in part one, is applied. The forecast ability of the models is systematically tested for several earthquake sequences and compared to models using random slip distributions. The influence of subfault resolution and segment strike and dip is tested. Some of the tested slip models perform very good, in that cases almost no random slip models are found to perform better. Contrastingly, for some of the published slip models, almost all random slip models perform better than the published slip model. Choosing a different subfault resolution hardly influences the result, as long the general slip pattern is still reproducible. Whereas different strike and dip values strongly influence the results depending on the standard deviation chosen, which is applied in the process of randomly selecting the strike and dip values.
N2  - Verschiedene Mechanismen werden für das Triggern von Erdbeben verantwortlich gemacht, darunter statische Spannungsänderungen und dynamischer Spannungstransfer. Deutliche Unterschiede zwischen diesen Mechanismen werden insbesondere in der räumlichen Nachbebenverteilung erwartet. Es ist allerdings schwierig diese Hypothesen zu überprüfen, da die großen Unsicherheiten der Spannungsberechnungen berücksichtigt werden müssen, ebenso wie das durch lokale sekundäre Spannungsänderungen hervorgerufene initiieren von sekundären Nachbeben. Um die Vorhersagekraft verschiedener Mechanismen zu beurteilen habe ich die Effekte von Erdbeben kleiner Magnitude durch Benutzen des "epidemic type aftershock sequence" (ETAS) Modells berücksichtigt. Dabei habe ich die Verteilung direkter Nachbeben, wenn verfügbar, mit alternativen Herdinformationen korreliert. Bodenbewegung, Bruchgeometrie und Slipmodelle werden getestet. Als Aproximation der Bodenbewegung werden ShakeMaps benutzt. Diese sind nach großen Erdbeben nahezu in Echtzeit verfügbar und können daher für vorläufige Vorhersagen der räumlichen Nachbebenverteilung benutzt werden. Alternativ können empirische Beziehungen als Funktion der minimalen Distanz zur Herdfläche benutzt werden oder Coulomb Spannungsänderungen basierend auf publizierten oder zufälligen Slipmodellen. Zum Vergleich werden die Likelihood Werte der Hybridmodelle im Falle mehrerer bekannter Nachbebensequenzen analysiert (1992 Landers, 1999 Hector Mine, 2004 Parkfield). Die Tests zeigen, dass die Herdgeometrie die wichtigste Zusatzinformation zur Verbesserung der Nachbebenvorhersage ist. Des Weiteren können statische Spannungsänderungen besonders die Vorhersage von Nachbeben in größerer Entfernung zur Bruchfläche verbessern, wohingegen die Einbeziehung von Bodenbewegungskarten die Ergebnisse nicht wesentlich verbessern konnte. Im zweiten Teil meiner Arbeit führe ich ein neues Verfahren zur Untersuchung des Informationsgehaltes von invertierten Slipmodellen ein. Dies ermöglicht die Quantifizierung des Informationsgewinns, der durch Einbeziehung dieser Daten in Nachbebenvorhersagen entsteht. Hierbei wird das im ersten Teil eingeführte erweiterte ETAS Modell benutzt, welches statische Spannungsänderung zur Vorhersage der räumlichen Nachbebenverteilung benutzt. Die Vorhersagekraft der Modelle wird systematisch anhand mehrerer Erdbebensequenzen untersucht und mit Modellen basierend auf zufälligen Slipverteilungen verglichen. Der Einfluss der Veränderung der Auflösung der Slipmodelle, sowie Streich- und Fallwinkel der Herdsegmente wird untersucht. Einige der betrachteten Slipmodelle korrelieren sehr gut, in diesen Fällen werden kaum zufällige Slipmodelle gefunden, welche die Nachbebenverteilung besser erklären. Dahingegen korrelieren bei einigen Beispielen nahezu alle zufälligen Slipmodelle besser als das publizierte Modell. Das Verändern der Auflösung der Bewegungsmodelle hat kaum Einfluss auf die Ergebnisse, solange die allgemeinen Slipmuster noch reproduzierbar sind, d.h. ein bis zwei größere Slipmaxima pro Segment. Dahingegen beeinflusst eine zufallsbasierte Änderung der Streich- und Fallwinkel der Segmente die Resultate stark, je nachdem welche Standardabweichung gewählt wurde.
KW  - Nachbeben
KW  - ETAS
KW  - Vorhersage
KW  - aftershock
KW  - ETAS
KW  - forecast
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-70591
ER  - 
TY  - JOUR
A1  - Bachmann, Raik
A1  - Oncken, Onno
A1  - Glodny, Johannes
A1  - Seifert, Wolfgang
A1  - Georgieva, Viktoria
A1  - Sudo, Masafumi
T1  - Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone
N2  - We present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central Alps of Europe related to Late Cretaceous-early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate. The material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation, thus reflecting a multistage evolution. Fabric formation and metamorphism, however, chiefly record the deformation conditions of the precollisional setting along the plate interface. We identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300 degrees C. This zone coincides with a domain of intense veining in the subduction melange with mineral growth into open cavities, indicating fast, possibly seismic, rupture. Evidence for transient near-lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes, possibly reflecting a zone of conditionally stable slip. The zone above the unstable slip area is devoid of veins but displays ample evidence of fluid-assisted processes similar to the deeper zone: solution-precipitation creep and dehydration reactions in the melange matrix, hydration, and sealing of the base of the upper plate. Seismic rupture here is possibly expressed by ubiquitous localized deformation zones. We hypothesize that trenchward sealing of parts of the plate interface as well as reaction-enhanced destruction of upper plate permeability is an important component, localizing the unstable slip zone. This relation may result from the competition of the pervasive, presumably interseismic, pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure.
Y1  - 2009
UR  - http://www.agu.org/journals/jb/
U6  - https://doi.org/10.1029/2008jb005927
SN  - 0148-0227
ER  - 
TY  - THES
A1  - Back, Stefan
T1  - Tectonics, Climate, and Sedimentation in the Northern Baikal Rift, Russia
Y1  - 1998
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - De Batist, Marc
A1  - Strecker, Manfred
T1  - The Frolikha Fan : a large Pleistocene glaciolacustrine outwash fan in northern Lake Baikal, Siberia
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - De Batist, Marc
A1  - Strecker, Manfred
A1  - Vanhauwaert, P.
T1  - Quaternary depositional systems in northern Lake Baikal, Siberia
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Back, Stefan
A1  - Strecker, Manfred
T1  - Asymmetric late Pleistocene glaciations in the North Basin of the Baikal Rift, Russia
Y1  - 1998
ER  - 
TY  - THES
A1  - Backers, Tobias
T1  - Fracture toughness determination and micromechanics of rock under Mode I and Mode II loading
N2  - This thesis work describes a new experimental method for the determination of Mode II (shear) fracture toughness, KIIC of rock and compares the outcome to results from Mode I (tensile) fracture toughness, KIC, testing using the International Society of Rock Mechanics Chevron-Bend method.Critical Mode I fracture growth at ambient conditions was studied by carrying out a series of experiments on a sandstone at different loading rates. The mechanical and microstructural data show that time- and loading rate dependent crack growth occurs in the test material at constant energy requirement.The newly developed set-up for determination of the Mode II fracture toughness is called the Punch-Through Shear test. Notches were drilled to the end surfaces of core samples. An axial load punches down the central cylinder introducing a shear load in the remaining rock bridge. To the mantle of the cores a confining pressure may be applied. The application of confining pressure favours the growth of Mode II fractures as large pressures suppress the growth of tensile cracks.Variation of geometrical parameters leads to an optimisation of the PTS- geometry. Increase of normal load on the shear zone increases KIIC bi-linear. High slope is observed at low confining pressures; at pressures above 30 MPa low slope increase is evident. The maximum confining pressure applied is 70 MPa. The evolution of fracturing and its change with confining pressure is described.The existence of Mode II fracture in rock is a matter of debate in the literature. Comparison of the results from Mode I and Mode II testing, mainly regarding the resulting fracture pattern, and correlation analysis of KIC and KIIC to physico-mechanical parameters emphasised the differences between the response of rock to Mode I and Mode II loading. On the microscale, neither the fractures resulting from Mode I the Mode II loading are pure mode fractures. On macroscopic scale, Mode I and Mode II do exist.
N2  - Diese Arbeit beschreibt eine neue experimentelle Methode zur Bestimmung der Modus II (Schub) Bruchzähigkeit, KIIC, von Gestein und vergleicht die Ergebnisse mit Resultaten aus Versuchen zur Bestimmung der Modus I (Zug) Bruchzähigkeit, KIC.An einer Serie von Versuchen mit verschiedenen Belastungsraten wurde das kritische Modus I Rißwachstum eines Sandsteines untersucht. Die mechanischen Daten zeigen, daß zeit- und belastungsratenabhängiges Rißwachstum in dem Material bei konstantem Energieverbrauch stattfindet. Der neu entwickelte Versuchsaufbau zur Ermittlung der Modus II Bruchzähigkeit wurde Punch- Through Shear Test genannt. Die Proben werden aus Bohrkernen hergestellt in deren Endflächen Nuten eingebracht werden. Eine Last auf den Innenzylinder induziert eine Schubspannung. Auf die Mantelfläche der Proben kann ein Umlagerungsdruck aufgebracht werden. Da durch Normalspannungen das Modus I Rißwachstum unterdrückt wird, wird das Modus II Rißwachstum gefördert.Die PTS- Probengeometrie wurde bezüglich Nutentiefe, -durchmessers, -breite und des Probendurchmessers optimiert. KIIC steigt bi-linear mit Zunahme des Umlagerungsdruckes an. Ein starker Anstieg ist bis zu Umlagerungsdrücken von etwa 30 MPa zu beobachten, oberhalb ist die Steigung geringer. Bisher wurden Umlagerungsdrücke bis maximal 70 MPa aufgebracht. Die Entwicklung der entstehenden Risse und deren Variation mit Umlagerungsdruck wird beschrieben.Ob die Entstehung eines Modus II Risses in Gestein möglich ist, wurde vielfach in der Literatur diskutiert. Der Vergleich der Ergebnisse der Modus I und II Experimente, insbesondere bezüglich der Rißmuster und der Korrelationsanalysen von KIC und KIIC zu physiko-mechanischen Parametern, zeigt die Unterschiede der Reaktion auf Modus I und Modus II Belastung auf. Mikroskopisch gesehen wachsen die Risse weder unter Modus I noch unter Modus II Belastung in einem reinen Modus. Allerdings existieren Modus I und Modus II Risse auf der makroskopischen Betrachtungsebene.
KW  - Rissmechanik
KW  - Felsmechanik
KW  - Bruchzähigkeit
KW  - Mikrostruktur
KW  - fracture mechanics
KW  - rock mechanics
KW  - fracture toughness
KW  - microsructure
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-2294
ER  - 
TY  - JOUR
A1  - Baes, Marzieh
A1  - Gerya, Taras V.
A1  - Sobolev, Stephan Vladimir
T1  - 3-D thermo-mechanical modeling of plume-induced subduction initiation
JF  - Earth & planetary science letters
N2  - Here, we study the 3-D subduction initiation process induced by the interaction between a hot thermochemical mantle plume and oceanic lithosphere using thermo-mechanical viscoplastic finite difference marker-in-cell models. Our numerical modeling results show that self-sustaining subduction is induced by plume-lithosphere interaction when the plume is sufficiently buoyant, the oceanic lithosphere is sufficiently old and the plate is weak enough to allow the buoyant plume to. pass through it. Subduction initiation occurs following penetration of the lithosphere by the hot plume and the downward displacement of broken, nearly circular segments of lithosphere (proto-slabs) as a result of partially molten plume rocks overriding the proto-slabs. Our experiments show four different deformation regimes in response to plume-lithosphere interaction: a) self-sustaining subduction initiation, in which subduction becomes self-sustaining; b) frozen subduction initiation, in which subduction stops at shallow depths; c) slab break-off, in which the subducting circular slab breaks off soon after formation; and d) plume underplating, in which the plume does not pass through the lithosphere and instead spreads beneath it (i.e., failed subduction initiation). These regimes depend on several parameters, such as the size, composition, and temperature of the plume, the brittle/plastic strength and age of the oceanic lithosphere, and the presence/absence of lithospheric heterogeneities. The results show that subduction initiates and becomes self-sustaining when the lithosphere is older than 10 Myr and the non dimensional ratio of the plume buoyancy force and lithospheric strength above the plume is higher than approximately 2. The outcomes of our numerical experiments are applicable for subduction initiation in the modern and Precambrian Earth and for the origin of plume-related corona structures on Venus. (C) 2016 Elsevier B.V. All rights reserved.
KW  - subduction initiation
KW  - mantle plume
KW  - oceanic lithosphere
KW  - numerical models
Y1  - 2016
U6  - https://doi.org/10.1016/j.epsl.2016.08.023
SN  - 0012-821X
SN  - 1385-013X
VL  - 453
SP  - 193
EP  - 203
PB  - Elsevier
CY  - Amsterdam
ER  -