TY  - GEN
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Öztürk, Ugur
A1  - Kurths, Jürgen
A1  - Merz, Bruno
T1  - Optimal design of hydrometric station networks based on complex network analysis
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Hydrometric networks play a vital role in providing information for decision-making in water resource management. They should be set up optimally to provide as much information as possible that is as accurate as possible and, at the same time, be cost-effective. Although the design of hydrometric networks is a well-identified problem in hydrometeorology and has received considerable attention, there is still scope for further advancement. In this study, we use complex network analysis, defined as a collection of nodes interconnected by links, to propose a new measure that identifies critical nodes of station networks. The approach can support the design and redesign of hydrometric station networks. The science of complex networks is a relatively young field and has gained significant momentum over the last few years in different areas such as brain networks, social networks, technological networks, or climate networks. The identification of influential nodes in complex networks is an important field of research. We propose a new node-ranking measure – the weighted degree–betweenness (WDB) measure – to evaluate the importance of nodes in a network. It is compared to previously proposed measures used on synthetic sample networks and then applied to a real-world rain gauge network comprising 1229 stations across Germany to demonstrate its applicability. The proposed measure is evaluated using the decline rate of the network efficiency and the kriging error. The results suggest that WDB effectively quantifies the importance of rain gauges, although the benefits of the method need to be investigated in more detail.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 951 
KW  - identifying influential nodes
KW  - climate networks
KW  - rainfall
KW  - streamflow
KW  - synchronization
KW  - precipitation
KW  - classification
KW  - events
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-471006
SN  - 1866-8372
IS  - 951
ER  - 
TY  - THES
A1  - Aich, Valentin
T1  - Floods in the Niger River Basin in the face of global change
T1  - Hochwasser im Niger Einzugsgebiet im Kontext des Globalen Wandels
BT  - analysis, attribution and projections
BT  - Analyse, Zuschreibung und Projektionen
N2  - In the last decade, the number and dimensions of catastrophic flooding events in the Niger River Basin (NRB) have markedly increased. Despite the devastating impact of the floods on the population and the mainly agriculturally based economy of the riverine nations, awareness of the hazards in policy and science is still low. The urgency of this topic and the existing research deficits are the motivation for the present dissertation.
The thesis is an initial detailed assessment of the increasing flood risk in the NRB. The research strategy is based on four questions regarding (1) features of the change in flood risk, (2) reasons for the change in the flood regime, (3) expected changes of the flood regime given climate and land use changes, and (4) recommendations from previous analysis for reducing the flood risk in the NRB.
The question examining the features of change in the flood regime is answered by means of statistical analysis. Trend, correlation, changepoint, and variance analyses show that, in addition to the factors exposure and vulnerability, the hazard itself has also increased significantly in the NRB, in accordance with the decadal climate pattern of West Africa. The northern arid and semi-arid parts of the NRB are those most affected by the changes.
As potential reasons for the increase in flood magnitudes, climate and land use changes are attributed by means of a hypothesis-testing framework. Two different approaches, based on either data analysis or simulation, lead to similar results, showing that the influence of climatic changes is generally larger compared to that of land use changes. Only in the dry areas of the NRB is the influence of land use changes comparable to that of climatic alterations.
Future changes of the flood regime are evaluated using modelling results. First ensembles of statistically and dynamically downscaled climate models based on different emission scenarios are analyzed. The models agree with a distinct increase in temperature. The precipitation signal, however, is not coherent. The climate scenarios are used to drive an eco-hydrological model. The influence of climatic changes on the flood regime is uncertain due to the unclear precipitation signal. Still, in general, higher flood peaks are expected. In a next step, effects of land use changes are integrated into the model. Different scenarios show that regreening might help to reduce flood peaks. In contrast, an expansion of agriculture might enhance the flood peaks in the NRB. Similarly to the analysis of observed changes in the flood regime, the impacts of climate- and land use changes for the future scenarios are also most severe in the dry areas of the NRB.
In order to answer the final research question, the results of the above analysis are integrated into a range of recommendations for science and policy on how to reduce flood risk in the NRB. The main recommendations include a stronger consideration of the enormous natural climate variability in the NRB and a focus on so called “no-regret” adaptation strategies which account for high uncertainty, as well as a stronger consideration of regional differences. Regarding the prevention and mitigation of catastrophic flooding, the most vulnerable and sensitive areas in the basin, the arid and semi-arid Sahelian and Sudano-Sahelian regions, should be prioritized. Eventually, an active, science-based and science-guided flood policy is recommended. The enormous population growth in the NRB in connection with the expected deterioration of environmental and climatic conditions is likely to enhance the region´s vulnerability to flooding. A smart and sustainable flood policy can help mitigate these negative impacts of flooding on the development of riverine societies in West Africa.
N2  - Während des vergangenen Jahrzehnts nahmen die Anzahl und die Ausmaße von katastrophalen Hochwassern im Einzugsgebiet des Nigerflussess (NEZG) deutlich zu. Trotz der verheerenden Auswirkungen der Hochwasserkatastrophen auf die Menschen und die hauptsächlich auf Landwirtschaft basierende Wirtschaft der Anrainerstaaten wird das Thema von Politik und Wissenschaft noch kaum beachtet.
Die vorliegende Dissertation ist die erste ausführliche Analyse des steigenden Hochwasserrisikos im NEZG. Die Forschungsstrategie basiert auf vier Fragen nach (1) der Art der Veränderungen des Hochwasserrisikos, (2) den Ursachen der Veränderungen im Hochwasserregime, (3) den zukünftigen Entwicklungen im Hochwasserregime hinsichtlich der erwartenden Klima- und Landnutzungswandel und (4) den aus den Untersuchungen abgeleiteten Empfehlungen zur Reduzierung des Hochwasserrisikos im NEZG.
Die Frage nach den Merkmalen der Veränderungen im Hochwasserrisiko wurde mithilfe von statistischen Untersuchungen beantwortet. Die Analysen zeigen, dass neben den Risikofaktoren Exponiertheit und Verwundbarkeit auch die Hochwasserstände selbst im NEZG in den letzten Jahrzehnten signifikant und entsprechend der typischen dekadischen Klimamuster Westafrikas angestiegen sind.
Als potentielle Ursachen des Hochwasseranstiegs werden Klima- und Landnutzungswandel untersucht. Zwei verschiedene Ansätze, basierend auf Daten sowie auf Simulationen, führen zu ähnlichen Ergebnissen und zeigen, dass der Einfluss der Klimaveränderungen im Allgemeinen größer als der des Landnutzungswandels ist.
Das zukünftige Hochwasserrisiko wird anhand des öko-hydrologisches Modells SWIM abgeschätzt. Der Einfluss des Klimawandels auf das Hochwasserregime ist auf Grund des problematischen Niederschlagssignals unsicher. Tendenziell werden aber höhere Maximalabflüsse erwartet. Der Effekt der Landnutzungsänderung beeinflusst das Hochwasserverhalten ebenfalls stark, besonders in den trockenen Gebieten. Verschiedene Szenarien zeigen, dass Renaturierung hülfe, Hochwasserspitzen zu kappen. Eine Ausweitung der Agrarflächen dagegen würde die Hochwässer im NEZG weiter verstärken
Zentrale Empfehlungen sind eine stärkere Einbeziehung der enorm starken natürlichen Klimavariabilität im NEZG und eine Fokussierung auf sogenannte „no-regret“ Anpassungsstrategien. Dabei sollte den verwundbarsten Regionen des Einzugsgebiets, den ariden und semi-ariden Regionen, Priorität eingeräumt werden. Die enorme Bevölkerungszunahme im NEZG verbunden mit der zu erwartenden Verschlechterung der Umwelt- und Klimabedingungen wird mit hoher Wahrscheinlichkeit auch die Verwundbarkeit bezüglich Hochwässer weiter ansteigen lassen. Eine vernünftige und nachhaltige Hochwasserpolitik kann helfen, die negativen Folgen auf die Entwicklung der Anrainerstaaten des Nigerflusses abzumindern.
KW  - flood
KW  - Niger
KW  - climate change
KW  - land use change
KW  - Hochwasser
KW  - Niger
KW  - Klimawandel
KW  - Landnutzungswandel
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-91577
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, T.
A1  - Huang, S.
A1  - Tecklenburg, J.
A1  - Hoffmann, P.
A1  - Koch, H.
A1  - Fournet, S.
A1  - Krysanova, Valentina
A1  - Mueller, N.
A1  - Hattermann, Fred
T1  - Comparing impacts of climate change on streamflow in four large African river basins
JF  - Hydrology and earth system sciences : HESS
N2  - This study aims to compare impacts of climate change on streamflow in four large representative African river basins: the Niger, the Upper Blue Nile, the Oubangui and the Limpopo. We set up the eco-hydrological model SWIM (Soil and Water Integrated Model) for all four basins individually. The validation of the models for four basins shows results from adequate to very good, depending on the quality and availability of input and calibration data.
 For the climate impact assessment, we drive the model with outputs of five bias corrected Earth system models of Coupled Model Intercomparison Project Phase 5 (CMIP5) for the representative concentration pathways (RCPs) 2.6 and 8.5. This climate input is put into the context of climate trends of the whole African continent and compared to a CMIP5 ensemble of 19 models in order to test their representativeness. Subsequently, we compare the trends in mean discharges, seasonality and hydrological extremes in the 21st century. The uncertainty of results for all basins is high. Still, climate change impact is clearly visible for mean discharges but also for extremes in high and low flows. The uncertainty of the projections is the lowest in the Upper Blue Nile, where an increase in streamflow is most likely. In the Niger and the Limpopo basins, the magnitude of trends in both directions is high and has a wide range of uncertainty. In the Oubangui, impacts are the least significant. Our results confirm partly the findings of previous continental impact analyses for Africa. However, contradictory to these studies we find a tendency for increased streamflows in three of the four basins (not for the Oubangui). Guided by these results, we argue for attention to the possible risks of increasing high flows in the face of the dominant water scarcity in Africa. In conclusion, the study shows that impact intercomparisons have added value to the adaptation discussion and may be used for setting up adaptation plans in the context of a holistic approach.
Y1  - 2014
U6  - https://doi.org/10.5194/hess-18-1305-2014
SN  - 1027-5606
SN  - 1607-7938
VL  - 18
IS  - 4
SP  - 1305
EP  - 1321
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, Tobias
A1  - Andersson, Jafet C. M.
A1  - Müller, Eva Nora
A1  - Hattermann, Fred
T1  - Climate or Land Use?
BT  - Attribution of Changes in River Flooding in the Sahel Zone
JF  - Water
N2  - This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950-2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.
Y1  - 2015
U6  - https://doi.org/10.3390/w7062796
SN  - 2073-4441
VL  - 7
IS  - 6
SP  - 2796
EP  - 2820
PB  - MDPI
CY  - Basel
ER  - 
TY  - GEN
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, Tobias
A1  - Andersson, Jafet C. M.
A1  - Müller, Eva Nora
A1  - Hattermann, Fred
T1  - Climate or land use?
BT  - Attribution of changes in river flooding in the Sahel Zone
N2  - This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950–2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 345 
KW  - simulation-based attribution
KW  - Sahel
KW  - Niger River
KW  - climate variability
KW  - hydrological modeling
KW  - flood mitigation
KW  - flood adaptation
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400115
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Zimmermann, Alexander
A1  - Elsenbeer, Helmut
T1  - Quantification and interpretation of suspended-sediment discharge hysteresis patterns: How much data do we need?
JF  - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution
N2  - Sediment-discharge hysteresis loops are frequently analyzed to facilitate the understanding of sediment transport processes. Hysteresis patterns, however, are often complex and their interpretation can be complicated. Particularly, quantifying hysteresis patterns remains a problematic issue. Moreover, it is currently unknown how much data is required for analyzing sediment-discharge hysteresis loops in a given area. These open questions and challenges motivated us to develop a new method for quantifying suspended-sediment hysteresis. Subsequently, we applied the new hysteresis index to three suspended-sediment and discharge datasets from a small tropical rainforest catchment. The datasets comprised a different number of events and sampling sites. Our analyses show three main findings: (1) datasets restricted to only few events, which is typical for rapid assessment surveys, were always sufficient to identify the dominating hysteresis pattern in our research area. Furthermore, some of these small datasets contained multiple-peak events that allowed identifying intra-event exhaustion effects and hence, limitations in sediment supply. (2) Datasets comprising complete hydrological years were particularly useful for analyzing seasonal dynamics of hysteresis. These analyses revealed an exhaustion of hysteresis on the inter-event scale which also points to a limited sediment supply. (3) Datasets comprising measurements from two consecutive gauges installed at the catchment outlet and on a slope within that catchment allowed analyzing the change of hysteresis patterns along the flowpath. On the slope, multiple-peak events showed a stronger intra-event exhaustion of hysteresis than at the catchment outlet. Furthermore, exhaustion of hysteresis on the inter-event scale was not evident on the slope but occurred at the catchment outlet. Our results indicate that even small sediment datasets can provide valuable insights into sediment transport processes of small catchments. Furthermore, our results may serve as a first guideline on what to expect from an analysis of hysteresis patterns for datasets of varying quality and quantity. (c) 2014 Elsevier B.V. All rights reserved.
KW  - Suspended sediment
KW  - Hysteresis index
KW  - Sediment monitoring
KW  - Overland flow
KW  - Tropical forest
Y1  - 2014
U6  - https://doi.org/10.1016/j.catena.2014.06.020
SN  - 0341-8162
SN  - 1872-6887
VL  - 122
SP  - 120
EP  - 129
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - THES
A1  - Aichner, Bernhard
T1  - Aquatic macrophyte-derived biomarkers as palaeolimnological proxies on the Tibetan Plateau
T1  - Biomarker von Wasserpflanzen als Klimaindikatoren auf dem tibetischen Hochplateau
N2  - The Tibetan Plateau is the largest elevated landmass in the world and profoundly influences atmospheric circulation patterns such as the Asian monsoon system. Therefore this area has been increasingly in focus of palaeoenvironmental studies. This thesis evaluates the applicability of organic biomarkers for palaeolimnological purposes on the Tibetan Plateau with a focus on aquatic macrophyte-derived biomarkers. Submerged aquatic macrophytes have to be considered to significantly influence the sediment organic matter due to their high abundance in many Tibetan lakes. They can show highly 13C-enriched biomass because of their carbon metabolism and it is therefore crucial for the interpretation of δ13C values in sediment cores to understand to which extent aquatic macrophytes contribute to the isotopic signal of the sediments in Tibetan lakes and in which way variations can be explained in a palaeolimnological context. Additionally, the high abundance of macrophytes makes them interesting as potential recorders of lake water δD. Hydrogen isotope analysis of biomarkers is a rapidly evolving field to reconstruct past hydrological conditions and therefore of special relevance on the Tibetan Plateau due to the direct linkage between variations of monsoon intensity and changes in regional precipitation / evaporation balances. A set of surface sediment and aquatic macrophyte samples from the central and eastern Tibetan Plateau was analysed for composition as well as carbon and hydrogen isotopes of n-alkanes. It was shown how variable δ13C values of bulk organic matter and leaf lipids can be in submerged macrophytes even of a single species and how strongly these parameters are affected by them in corresponding sediments. The estimated contribution of the macrophytes by means of a binary isotopic model was calculated to be up to 60% (mean: 40%) to total organic carbon and up to 100% (mean: 66%) to mid-chain n-alkanes. Hydrogen isotopes of n-alkanes turned out to record δD of meteoric water of the summer precipitation. The apparent enrichment factor between water and n-alkanes was in range of previously reported ones (≈-130‰) at the most humid sites, but smaller (average: -86‰) at sites with a negative moisture budget. This indicates an influence of evaporation and evapotranspiration on δD of source water for aquatic and terrestrial plants. The offset between δD of mid- and long-chain n-alkanes was close to zero in most of the samples, suggesting that lake water as well as soil and leaf water are affected to a similar extent by those effects. To apply biomarkers in a palaeolimnological context, the aliphatic biomarker fraction of a sediment core from Lake Koucha (34.0° N; 97.2° E; eastern Tibetan Plateau) was analysed for concentrations, δ13C and δD values of compounds. Before ca. 8 cal ka BP, the lake was dominated by aquatic macrophyte-derived mid-chain n-alkanes, while after 6 cal ka BP high concentrations of a C20 highly branched isoprenoid compound indicate a predominance of phytoplankton. Those two principally different states of the lake were linked by a transition period with high abundances of microbial biomarkers. δ13C values were relatively constant for long-chain n-alkanes, while mid-chain n-alkanes showed variations between -23.5 to -12.6‰. Highest values were observed for the assumed period of maximum macrophyte growth during the late glacial and for the phytoplankton maximum during the middle and late Holocene. Therefore, the enriched values were interpreted to be caused by carbon limitation which in turn was induced by high macrophyte and primary productivity, respectively. Hydrogen isotope signatures of mid-chain n-alkanes have been shown to be able to track a previously deduced episode of reduced moisture availability between ca. 10 and 7 cal ka BP, indicated by a 20‰ shift towards higher δD values. Indications for cooler episodes at 6.0, 3.1 and 1.8 cal ka BP were gained from drops of biomarker concentrations, especially microbial-derived hopanoids, and from coincidental shifts towards lower δ13C values. Those episodes correspond well with cool events reported from other locations on the Tibetan Plateau as well as in the Northern Hemisphere. To conclude, the study of recent sediments and plants improved the understanding of factors affecting the composition and isotopic signatures of aliphatic biomarkers in sediments. Concentrations and isotopic signatures of the biomarkers in Lake Koucha could be interpreted in a palaeolimnological context and contribute to the knowledge about the history of the lake. Aquatic macrophyte-derived mid-chain n-alkanes were especially useful, due to their high abundance in many Tibetan Lakes and their ability to record major changes of lake productivity and palaeo-hydrological conditions. Therefore, they have the potential to contribute to a fuller understanding of past climate variability in this key region for atmospheric circulation systems.
N2  - Das tibetische Hochplateau ist die größte gehobene Landmasse der Erde und beeinflusst maßgeblich atmosphärische Zirkulationsmuster wie den Asiatischen Monsun. Um die Auswirkungen zukünftiger Schwankungen der Monsundynamik auf das regionale Klima besser einschätzen zu können, ist es wichtig, ein fundiertes Verständnis vergangener Klimaänderungen zu entwickeln. Daher ist das Tibetplateau in den letzten Jahren mehr und mehr in den Fokus paläoklimatischer Studien gerückt. Die große Anzahl an Seen in der Region bietet ein unerschöpfliches Klimaarchiv und viele Studien haben sich bereits mit Seesedimenten zur Klimarekonstruktion befasst. Dabei wurde in erster Linie auf biologische, sedimentologische und geochemische Parameter zurückgegriffen, wohingegen organische Biomarker bisher recht selten benutzt wurden. Die vorliegende Arbeit untersucht die Anwendbarkeit dieser potentiellen Klimaindikatoren auf dem Tibetplateau. Hierbei wurde ein Schwerpunkt auf die Analyse kutikularer Blattwachse von Wasserpflanzen gelegt, da diese wegen ihres starken Auftretens in tibetischen Seen einen erheblichen Beitrag zur organischen Substanz im Sediment leisten. Um den Einfluss von Wasserpflanzen auf das Sediment über einen weiten klimatischen Gradienten zu untersuchen, wurden Oberflächensedimente und Wasserpflanzen vom zentralen und östlichen Tibetplateau auf ihre Biomarkerzusammensetzung sowie auf ihre Kohlen- und Wasserstoffisotopensignatur untersucht. Dadurch wurde das Verständnis über beeinflussende Faktoren auf diese Parameter in Sedimenten vertieft. In einem Sedimentbohrkern des Koucha-Sees (östliches Tibetplateau) konnten diese Parameter dann im Hinblick auf Änderungen der Produktivität im See sowie der hydrologischen und klimatischen Bedingungen der letzten 15000 Jahre interpretiert werden. Es zeigte sich, dass der See bis 8000 Jahre vor Heute stark mit Wasserpflanzen bewachsen war, während die letzten 6000 Jahre Algen dominierten. Mit Hilfe von Wasserstoffisotopen wurden eine Zunahme des Monsuns und steigende Niederschläge zwischen 15000 und 10000 Jahren vor Heute sowie eine relativ trockene Periode zwischen 10000 und 7000 Jahren vor Heute rekonstruiert. Durch Kombination von Biomarkerkonzentrationen sowie deren Kohlenstoffisotopensignal wurden außerdem kurzzeitige Kälteperioden um ca. 6000, 3100 und 1800 Jahren vor Heute nachgewiesen, die vorher bereits in anderen Klimaarchiven in Tibet sowie auf der nördlichen Hemisphäre belegt wurden. Mit Hilfe von organischen Biomarkern konnte so ein detailliertes Bild über die Entwicklung des Koucha-Sees seit dem letzten Glazial gewonnen werden. Organische Biomarker haben sich somit als geeignet erwiesen, einen Beitrag zur Klimarekonstruktion auf dem Tibetplateau zu leisten.
KW  - Biomarker
KW  - Isotope
KW  - Tibet
KW  - Paläolimnologie
KW  - Klima
KW  - Wasserpflanzen
KW  - biomarker
KW  - isotopes
KW  - Tibetan Plateau
KW  - palaeolimnology
KW  - climate
KW  - macrophytes
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42095
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Bussian, Bernd M.
A1  - Lehnik-Habrink, Petra
A1  - Hein, Sebastian
T1  - Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils
JF  - Environmental pollution
N2  - Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to more Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints. (C) 2015 Elsevier Ltd. All rights reserved.
KW  - Organic pollutants
KW  - PAHs
KW  - Soil
KW  - Emissions
KW  - Long-range transport
KW  - Enrichment factor
KW  - Humic layer
KW  - Mineral soil
KW  - O horizon
Y1  - 2015
U6  - https://doi.org/10.1016/j.envpol.2015.03.026
SN  - 0269-7491
SN  - 1873-6424
VL  - 203
SP  - 31
EP  - 39
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Feakins, Sarah J.
A1  - Lee, J. E.
A1  - Herzschuh, Ulrike
A1  - Liu, X.
T1  - High-resolution leaf wax carbon and hydrogen isotopic record of the late Holocene paleoclimate in arid Central Asia
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Central Asia is located at the confluence of large-scale atmospheric circulation systems. It is thus likely to be highly susceptible to changes in the dynamics of those systems; however, little is still known about the regional paleoclimate history. Here we present carbon and hydrogen isotopic compositions of n-alkanoic acids from a late Holocene sediment core from Lake Karakuli (eastern Pamir, Xinjiang Province, China). Instrumental evidence and isotopeenabled climate model experiments with the Laboratoire de Meteorologie Dynamique Zoom model version 4 (LMDZ4) demonstrate that delta D values of precipitation in the region are influenced by both temperature and precipitation amount. We find that these parameters are inversely correlated on an annual scale, i.e., the climate has varied between relatively cool and wet and more warm and dry over the last 50 years. Since the isotopic signals of these changes are in the same direction and therefore additive, isotopes in precipitation are sensitive recorders of climatic changes in the region. Additionally, we infer that plants use year-round precipitation (including snowmelt), and thus leaf wax delta D values must also respond to shifts in the proportion of moisture derived from westerly storms during late winter and early spring. Downcore results give evidence for a gradual shift to cooler and wetter climates between 3.5 and 2.5 cal kyr BP, interrupted by a warm and dry episode between 3.0 and 2.7 kyr BP. Further cool and wet episodes occur between 1.9 and 1.5 and between 0.6 and 0.1 kyr BP, the latter coeval with the Little Ice Age. Warm and dry episodes from 2.5 to 1.9 and 1.5 to 0.6 kyr BP coincide with the Roman Warm Period and Medieval Climate Anomaly, respectively. Finally, we find a drying tend in recent decades. Regional comparisons lead us to infer that the strength and position of the westerlies, and wider northern hemispheric climate dynamics, control climatic shifts in arid Central Asia, leading to complex local responses. Our new archive from Lake Karakuli provides a detailed record of the local signatures of these climate transitions in the eastern Pamir.
Y1  - 2015
U6  - https://doi.org/10.5194/cp-11-619-2015
SN  - 1814-9324
SN  - 1814-9332
VL  - 11
IS  - 4
SP  - 619
EP  - 633
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Herzschuh, Ulrike
A1  - Wilkes, Heinz
A1  - Schulz, Hans-Martin
A1  - Wang, Yongbo
A1  - Plessen, Birgit
A1  - Mischke, Steffen
A1  - Diekmann, Bernhard
A1  - Zhang, Chengjun
T1  - Ecological development of Lake Donggi Cona, north-eastern Tibetan Plateau, since the late glacial on basis of organic geochemical proxies and non-pollen palynomorphs
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - Organic geochemical proxy data from surface sediment samples and a sediment core from Lake Donggi Cona were used to infer environmental changes on the northeastern Tibetan Plateau spanning the last 18.4 kyr. Long-chain n-alkanes dominate the aliphatic hydrocarbon fraction of the sediment extract from most surface sediment samples and the sediment core. Unsaturated mid-chain n-alkanes (nC(23:1) and nC(25:1)) have high abundances in some samples, especially in core samples from the late glacial and early Holocene. TOC contents, organic biomarker and non-pollen-palynomorph concentrations and results from organic petrologic analysis on selected samples suggest three major episodes in the history of Lake Donggi Cona. Before ca. 12.6 cal ka BP samples contain low amounts of organic matter due to cold and arid conditions during the late glacial. After 12.6 cal ka BP, relatively high contents of TOC and concentrations of Botryococcus fossils, as well as enhanced concentrations of mid-chain n-alkanes and n-alkenes suggest a higher primary and macrophyte productivity than at present This is supported by high contents of palynomorphs derived from higher plants and algae and was possibly triggered by a decrease of salinity and amelioration of climate during the early Holocene. Since 6.8 cal ka BP Lake Donggi Cona has been an oligotrophic freshwater lake. Proxy data suggest that variations in insolation drive ecological changes in the lake, with increased aquatic productivity during the early Holocene summer insolation maximum. Short-term drops of TOC contents or biomarker concentrations (at 9.9 cal ka BP, after 8.0 and between 3.5 and 1.7 cal ka BP) can possibly be related to relatively cool and dry episodes reported from other sites on the north-eastern Tibetan Plateau, which are hypothesized to occur in phase with Northern Hemisphere cooling events.
KW  - Biomarker
KW  - Holocene
KW  - n-alkanes
KW  - Total organic carbon
KW  - Organic matter
KW  - Macerals
KW  - Aquatic macrophytes
Y1  - 2012
U6  - https://doi.org/10.1016/j.palaeo.2011.10.015
SN  - 0031-0182
VL  - 313
IS  - 2
SP  - 140
EP  - 149
PB  - Elsevier
CY  - Amsterdam
ER  - 
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  -