@phdthesis{Pingel2015,
  author    = {Pingel, Heiko},
  title     = {Mountain-range uplift \& climate-system interactions in the Southern Central Andes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-82301},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xii, 178},
  year      = {2015},
  abstract  = {Zwei h{\"a}ufig diskutierte Aspekte der sp{\"a}tk{\"a}nozoischen Gebirgsbildung der Anden sind der Zeitpunkt sowie die Art und Weise der Heraushebung des Puna-Plateaus und seiner Randgebiete innerhalb der Ostkordillere und die damit verbundenen klimatischen {\"A}nderungen in NW Argentinien. Die Ostkordillere trennt die Bereiche des endorheischen, ariden Plateaus von semiariden und extern entw{\"a}sserten intermontanen Becken sowie dem humiden Andenvorland im Osten. Diese Unterschiede verdeutlichen die Bedeutung der {\"o}stlichen Flanken der Anden als orografische Barrieren gegen{\"u}ber feuchten Luftmassen aus dem Osten und spiegelt sich auch in ausgepr{\"a}gten Relief- und Topografiegradienten, der Niederschlagsverteilung, und der Effizienz von Oberfl{\"a}chenprozessen wider. Obwohl das {\"u}bergeordnete Deformationsmuster in diesem Teil der Anden eine ostw{\"a}rts gerichtete Wanderung der Deformationsprozesse im Gebirge indiziert, gibt es hier keine klar definierte Deformationsfront. Hebungsvorg{\"a}nge und die damit im Zusammenhang stehenden Sedimentprozesse setzen r{\"a}umlich und zeitlich sehr unterschiedlich ein. Zudem gestalten periodisch wiederkehrende Deformationsereignisse innerhalb intermontaner Becken und diachrone Hebungsvorg{\"a}nge, durch Reaktivierung {\"a}lterer Sockelstrukturen im Vorland, eine detaillierte Auswertung der r{\"a}umlich-zeitlichen Hebungsmuster zus{\"a}tzlich schwierig. Die vorliegende Arbeit konzentriert sich haupts{\"a}chlich auf die tektonische Entwicklung der Ostkordillere im Nordwesten Argentiniens, die Ablagerungsgeschichte ihrer intermontanen Sedimentbecken und die topografische Entwicklung der Ostflanke des andinen Puna-Plateaus. Im Allgemeinen sind sich die Sedimentbecken der Ostkordillere und der angrenzenden Provinzen, den Sierras Pampeanas und der Santa B{\´a}rbara Region, den durch St{\"o}rungen begrenzten und mit Sedimenten verf{\"u}llten Becken der hochandinen Plateauregion sehr {\"a}hnlich. Deutliche Unterschiede zur Puna bestehen aber dennoch, denn wiederholte Deformations-, Erosions- und Sedimentationsprozesse haben in den intermontanen Becken zu einer vielf{\"a}ltigen Stratigrafie, {\"U}berlagerungsprozessen und einer durch tektonische Prozesse und klimatischen Wandel charakterisierten Landschaft beigetragen. Je nach Erhaltungsgrad k{\"o}nnen in einigen F{\"a}llen Spuren dieser sediment{\"a}ren und tektonischen Entwicklung bis in die Zeit zur{\"u}ckreichen, als diese Bereiche des Gebirges noch Teil eines zusammenh{\"a}ngenden und unverformten Vorlandbeckens waren. Im Nordwesten Argentiniens enthalten k{\"a}nozoische Sedimente zahlreiche datierbare und geochemisch korrelierbare Vulkanaschen, die nicht nur als wichtige Leithorizonte zur Entschl{\"u}sselung tektonischer und sediment{\"a}rer Ereignisse dienen. Die vulkanischen Gl{\"a}ser dieser Aschen archivieren außerdem Wasserstoff-Isotopenverh{\"a}ltnisse fr{\"u}herer Oberfl{\"a}chenwasser, mit deren Hilfe - im Vergleich mit den Isotopenverh{\"a}ltnissen rezenter meteorischer W{\"a}sser - die r{\"a}umliche und zeitliche Entstehung orografischer Barrieren und tektonisch erzwungene Klima- und Umweltver{\"a}nderungen verfolgt werden k{\"o}nnen. Uran-Blei-Datierungen an Zirkonen aus den vulkanischen Aschelagen und die Rekonstruktion sediment{\"a}rer Pal{\"a}otransportrichtungen im intermontanen Humahuaca-Becken in der Ostkordillere (23.5° S) deuten an, dass das heutige Becken bis vor etwa 4.2 Ma Bestandteil eines gr{\"o}ßtenteils uneingeschr{\"a}nkten Ablagerungsbereichs war, der sich bis ins Vorland erstreckt haben muss. Deformation und Hebung {\"o}stlich des heutigen Beckens sorgten dabei f{\"u}r eine fortschreitende Entkopplung des Entw{\"a}sserungsnetzes vom Vorland und eine Umlenkung der Flussl{\"a}ufe nach S{\"u}den. In der Folge erzwang die weitere Hebung der Gebirgsbl{\"o}cke das Abregnen {\"o}stlicher Luftmassen in immer {\"o}stlicher gelegene Bereiche. Zudem k{\"o}nnen periodische Schwankungen der hydrologischen Verbindung des Beckens mit dem Vorland im Zusammenhang mit der Ablagerung und Erosion m{\"a}chtiger Beckenf{\"u}llungen identifiziert werden. Systematische Beziehungen zwischen Verwerfungen, regionalen Diskontinuit{\"a}ten und verstellten Terrassenfl{\"a}chen verweisen außerdem auf ein generelles Muster beckeninterner Deformation, vermutlich als Folge umfangreicher Beckenerosion und damit verbundenen {\"A}nderungen im tektonischen Spannungsfeld der Region. Einige dieser Beobachtungen k{\"o}nnen anhand ver{\"a}nderter Wasserstoff-Isotopenkonzentrationen vulkanischer Gl{\"a}ser aus der k{\"a}nozoischen Stratigrafie untermauert werden. Die δDg-Werte zeigen zwei wesentliche Trends, die einerseits in Verbindung mit Oberfl{\"a}chenhebung innerhalb des Einzugsgebiets zwischen 6.0 und 3.5 Ma stehen und andererseits mit dem Einsetzen semiarider Bedingungen durch Erreichen eines Schwellenwertes der Topografie der {\"o}stlich gelegenen Gebirgsz{\"u}ge nach 3.5 Ma erkl{\"a}rt werden k{\"o}nnen. Tektonisch bedingte Unterbrechung der Sedimentzufuhr aus westlich gelegenen Liefergebieten um 4.2 Ma und die folgende Hinterland-Aridifizierung deuten weiterhin auf die M{\"o}glichkeit hin, dass diese Prozesse die Folge eines lateralen Wachstums des Puna-Plateaus sind. Diese Aridifizierung im Bereich der Puna resultierte in einem ineffizienten, endorheischen Entw{\"a}sserungssystem, das dazu beigetragen hat, das Plateau vor Einschneidung und externer Entw{\"a}sserung zu bewahren und Reliefgegens{\"a}tze aufgrund fortgesetzter Beckensedimentation reduzierte. Die diachrone Natur der Hebungen und Beckenbildungen sowie deren Auswirkungen auf das Flusssystem im angrenzenden Vorland wird sowohl durch detaillierte Analysen der Sedimentherkunft und Transportrichtungen als auch Uran-Blei-Datierungen im Lerma- und Met{\´a}n-Becken (25° S) weiterhin unterstrichen. Das wird besonders deutlich am Beispiel der isolierten Hebung der Sierra de Met{\´a}n vor etwa 10 Ma, die mehr als 50 km von der aktiven orogenen Front im Westen entfernt liegt. Ab 5 Ma sind typische Lithologien der Puna nicht mehr in den Vorlandsedimenten nachweisbar, welches die weitere Hebung innerhalb der Ostkordillere und die hydrologische Isolation des Angastaco-Beckens in dieser Region dokumentiert. Im Sp{\"a}tplioz{\"a}n und Quart{\"a}r ist die Deformation letztlich {\"u}ber das gesamte Vorland verteilt und bis heute aktiv. Um die Beziehungen zwischen tektonisch kontrollierten Ver{\"a}nderungen der Topografie und deren Einfluss auf atmosph{\"a}rische Prozesse besser zu verstehen, werden in dieser Arbeit weitere altersspezifische Wasserstoff-Isotopendaten vulkanischer Gl{\"a}ser aus dem zerbrochenen Vorland, dem Angastaco-Becken in der {\"U}bergangsregion zwischen Ostkordillere und Punarand und anderer intermontaner Becken weiter s{\"u}dlich vorgestellt. Die Resultate dokumentieren {\"a}hnliche H{\"o}henlagen der untersuchten Regionen bis ca. 7 Ma, gefolgt von Hebungsprozessen im Bereich des Angastaco-Beckens. Ein Vergleich mit Isotopendaten vom benachbarten Puna-Plateau hilft abrupte δDg-Schwankungen in den intermontanen Daten zu erkl{\"a}ren und untermauert die Existenz wiederkehrender Phasen verst{\"a}rkt konvektiver Wetterlagen im Plioz{\"a}n, {\"a}hnlich heutigen Bedingungen. In dieser Arbeit werden gel{\"a}ndeorientierte und geochemische Methoden kombiniert, um Erkenntnisse {\"u}ber die Abl{\"a}ufe von topografiebildenden Deformations- und Hebungsprozessen zu gewinnen und Wechselwirkungen mit der daraus resultierenden Niederschlagsverteilung, Erosion und Sedimentation innerhalb tektonisch aktiver Gebirge zu erforschen. Diese Erkenntnisse sind f{\"u}r ein besseres Verst{\"a}ndnis von Subduktionsgebirgen essentiell, besonders hinsichtlich des Deformationsstils und der zeitlich-r{\"a}umlichen Beziehungen bei der Hebung und Sedimentbeckenbildung. Diese Arbeit weist dar{\"u}berhinaus auf die Bedeutung stabiler Isotopensysteme zur Beantwortung pal{\"a}oaltimetrischer Fragestellungen und zur Erforschung von Pal{\"a}oumweltbedingungen hin und liefert wichtige Erkenntnisse f{\"u}r einen kritischen Umgang mit solchen Daten in anderen Regionen.},
  language  = {en}
}
@phdthesis{Olen2016,
  author    = {Olen, Stephanie M.},
  title     = {Understanding Himalayan denudation at the catchment and orogen scale},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-91423},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xx, 174},
  year      = {2016},
  abstract  = {Understanding the rates and processes of denudation is key to unraveling the dynamic processes that shape active orogens. This includes decoding the roles of tectonic and climate-driven processes in the long-term evolution of high- mountain landscapes in regions with pronounced tectonic activity and steep climatic and surface-process gradients. Well-constrained denudation rates can be used to address a wide range of geologic problems. In steady-state landscapes, denudation rates are argued to be proportional to tectonic or isostatic uplift rates and provide valuable insight into the tectonic regimes underlying surface denudation. The use of denudation rates based on terrestrial cosmogenic nuclide (TCN) such as 10Beryllium has become a widely-used method to quantify catchment-mean denudation rates. Because such measurements are averaged over timescales of 102 to 105 years, they are not as susceptible to stochastic changes as shorter-term denudation rate estimates (e.g., from suspended sediment measurements) and are therefore considered more reliable for a comparison to long-term processes that operate on geologic timescales. However, the impact of various climatic, biotic, and surface processes on 10Be concentrations and the resultant denudation rates remains unclear and is subject to ongoing discussion. In this thesis, I explore the interaction of climate, the biosphere, topography, and geology in forcing and modulating denudation rates on catchment to orogen scales. There are many processes in highly dynamic active orogens that may effect 10Be concentrations in modern river sands and therefore impact 10Be-derived denudation rates. The calculation of denudation rates from 10Be concentrations, however, requires a suite of simplifying assumptions that may not be valid or applicable in many orogens. I investigate how these processes affect 10Be concentrations in the Arun Valley of Eastern Nepal using 34 new 10Be measurements from the main stem Arun River and its tributaries. The Arun Valley is characterized by steep gradients in climate and topography, with elevations ranging from <100 m asl in the foreland basin to >8,000 asl in the high sectors to the north. This is coupled with a five-fold increase in mean annual rainfall across strike of the orogen. Denudation rates from tributary samples increase toward the core of the orogen, from <0.2 to >5 mm/yr from the Lesser to Higher Himalaya. Very high denudation rates (>2 mm/yr), however, are likely the result of 10Be TCN dilution by surface and climatic processes, such as large landsliding and glaciation, and thus may not be representative of long-term denudation rates. Mainstem Arun denudation rates increase downstream from ~0.2 mm/yr at the border with Tibet to 0.91 mm/yr at its outlet into the Sapt Kosi. However, the downstream 10Be concentrations may not be representative of the entire upstream catchment. Instead, I document evidence for downstream fining of grains from the Tibetan Plateau, resulting in an order-of-magnitude apparent decrease in the measured 10Be concentration. In the Arun Valley and across the Himalaya, topography, climate, and vegetation are strongly interrelated. The observed increase in denudation rates at the transition from the Lesser to Higher Himalaya corresponds to abrupt increases in elevation, hillslope gradient, and mean annual rainfall. Thus, across strike (N-S), it is difficult to decipher the potential impacts of climate and vegetation cover on denudation rates. To further evaluate these relationships I instead took advantage of an along-strike west-to-east increase of mean annual rainfall and vegetation density in the Himalaya. An analysis of 136 published 10Be denudation rates from along strike of the revealed that median denudation rates do not vary considerably along strike of the Himalaya, ~1500 km E-W. However, the range of denudation rates generally decreases from west to east, with more variable denudation rates in the northwestern regions of the orogen than in the eastern regions. This denudation rate variability decreases as vegetation density increases (R=- 0.90), and increases proportionately to the annual seasonality of vegetation (R=0.99). Moreover, rainfall and vegetation modulate the relationship between topographic steepness and denudation rates such that in the wet, densely vegetated regions of the Himalaya, topography responds more linearly to changes in denudation rates than in dry, sparsely vegetated regions, where the response of topographic steepness to denudation rates is highly nonlinear. Understanding the relationships between denudation rates, topography, and climate is also critical for interpreting sedimentary archives. However, there is a lack of understanding of how terrestrial organic matter is transported out of orogens and into sedimentary archives. Plant wax lipid biomarkers derived from terrestrial and marine sedimentary records are commonly used as paleo- hydrologic proxy to help elucidate these problems. I address the issue of how to interpret the biomarker record by using the plant wax isotopic composition of modern suspended and riverbank organic matter to identify and quantify organic matter source regions in the Arun Valley. Topographic and geomorphic analysis, provided by the 10Be catchment-mean denudation rates, reveals that a combination of topographic steepness (as a proxy for denudation) and vegetation density is required to capture organic matter sourcing in the Arun River. My studies highlight the importance of a rigorous and careful interpretation of denudation rates in tectonically active orogens that are furthermore characterized by strong climatic and biotic gradients. Unambiguous information about these issues is critical for correctly decoding and interpreting the possible tectonic and climatic forces that drive erosion and denudation, and the manifestation of the erosion products in sedimentary archives.},
  language  = {en}
}
@phdthesis{LauerDuenkelberg2023,
  author    = {Lauer-D{\"u}nkelberg, Gregor},
  title     = {Extensional deformation and landscape evolution of the Central Andean Plateau},
  doi       = {10.25932/publishup-61759},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-617593},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xviii, 195},
  year      = {2023},
  abstract  = {Mountain ranges can fundamentally influence the physical and and chemical processes that shape Earths' surface. With elevations of up to several kilometers they create climatic enclaves by interacting with atmospheric circulation and hydrologic systems, thus leading to a specific distribution of flora and fauna. As a result, the interiors of many Cenozoic mountain ranges are characterized by an arid climate, internally drained and sediment-filled basins, as well as unique ecosystems that are isolated from the adjacent humid, low-elevation regions along their flanks and forelands. These high-altitude interiors of orogens are often characterized by low relief and coalesced sedimentary basins, commonly referred to as plateaus, tectono-geomorphic entities that result from the complex interactions between mantle-driven geological and tectonic conditions and superposed atmospheric and hydrological processes. The efficiency of these processes and the fate of orogenic plateaus is therefore closely tied to the balance of constructive and destructive processes - tectonic uplift and erosion, respectively. In numerous geological studies it has been shown that mountain ranges are delicate systems that can be obliterated by an imbalance of these underlying forces. As such, Cenozoic mountain ranges might not persist on long geological timescales and will be destroyed by erosion or tectonic collapse. Advancing headward erosion of river systems that drain the flanks of the orogen may ultimately sever the internal drainage conditions and the maintenance of storage of sediments within the plateau, leading to destruction of plateau morphology and connectivity with the foreland. Orogenic collapse may be associated with the changeover from a compressional stress field with regional shortening and topographic growth, to a tensional stress field with regional extensional deformation and ensuing incision of the plateau. While the latter case is well-expressed by active extensional faults in the interior parts of the Tibetan Plateau and the Himalaya, for example, the former has been attributed to have breached the internally drained areas of the high-elevation sectors of the Iranian Plateau. In the case of the Andes of South America and their internally drained Altiplano-Puna Plateau, signs of both processes have been previously described. However, in the orogenic collapse scenario the nature of the extensional structures had been primarily investigated in the northern and southern terminations of the plateau; in some cases, the extensional faults were even regarded to be inactive. After a shallow earthquake in 2020 within the Eastern Cordillera of Argentina that was associated with extensional deformation, the state of active deformation and the character of the stress field in the central parts of the plateau received renewed interest to explain a series of extensional structures in the northernmost sectors of the plateau in north-western Argentina. This study addresses (1) the issue of tectonic orogenic collapse of the Andes and the destruction of plateau morphology by studying the fill and erosion history of the central eastern Andean Plateau using sedimentological and geochronological data and (2) the kinematics, timing and magnitude of extensional structures that form well-expressed fault scarps in sediments of the regional San Juan del Oro surface, which is an integral part of the Andean Plateau and adjacent morphotectonic provinces to the east. Importantly, sediment properties and depositional ages document that the San Juan del Oro Surface was not part of the internally-drained Andean Plateau, but rather associated with a foreland-directed drainage system, which was modified by the Andean orogeny and that became successively incorporated into the orogen by the eastward-migration of the Andean deformation front during late Miocene - Pliocene time. Structural and geomorphic observations within the plateau indicate that extensional processes must have been repeatedly active between the late Miocene and Holocene supporting the notion of plateau-wide extensional processes, potentially associated with Mw ~ 7 earthquakes. The close relationship between extensional joints and fault orientations underscores that 3 was oriented horizontally in NW-SE direction and 1 was vertical. This unambiguously documents that the observed deformation is related to gravitational forces that drive the orogenic collapse of the plateau. Applied geochronological analyses suggest that normal faulting in the northern Puna was active at about 3 Ma, based on paired cosmogenic nuclide dating of sediment fill units. Possibly due to regional normal faulting the drainage system within the plateau was modified, promoting fluvial incision.},
  language  = {en}
}
@phdthesis{KonradSchmolke2016,
  author    = {Konrad-Schmolke, Matthias},
  title     = {Thermodynamic and geochemical modeling in metamorphic geology},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-101805},
  school      = {Universit{\"a}t Potsdam},
  pages     = {232},
  year      = {2016},
  abstract  = {Quantitative thermodynamic and geochemical modeling is today applied in a variety of geological environments from the petrogenesis of igneous rocks to the oceanic realm. Thermodynamic calculations are used, for example, to get better insight into lithosphere dynamics, to constrain melting processes in crust and mantle as well as to study fluid-rock interaction. The development of thermodynamic databases and computer programs to calculate equilibrium phase diagrams have greatly advanced our ability to model geodynamic processes from subduction to orogenesis. However, a well-known problem is that despite its broad application the use and interpretation of thermodynamic models applied to natural rocks is far from straightforward. For example, chemical disequilibrium and/or unknown rock properties, such as fluid activities, complicate the application of equilibrium thermodynamics. One major aspect of the publications presented in this Habilitationsschrift are new approaches to unravel dynamic and chemical histories of rocks that include applications to chemically open system behaviour. This approach is especially important in rocks that are affected by element fractionation due to fractional crystallisation and fluid loss during dehydration reactions. Furthermore, chemically open system behaviour has also to be considered for studying fluid-rock interaction processes and for extracting information from compositionally zoned metamorphic minerals. In this Habilitationsschrift several publications are presented where I incorporate such open system behaviour in the forward models by incrementing the calculations and considering changing reacting rock compositions during metamorphism. I apply thermodynamic forward modelling incorporating the effects of element fractionation in a variety of geodynamic and geochemical applications in order to better understand lithosphere dynamics and mass transfer in solid rocks. In three of the presented publications I combine thermodynamic forward models with trace element calculations in order to enlarge the application of geochemical numerical forward modeling. In these publications a combination of thermodynamic and trace element forward modeling is used to study and quantify processes in metamorphic petrology at spatial scales from µm to km. In the thermodynamic forward models I utilize Gibbs energy minimization to quantify mineralogical changes along a reaction path of a chemically open fluid/rock system. These results are combined with mass balanced trace element calculations to determine the trace element distribution between rock and melt/fluid during the metamorphic evolution. Thus, effects of mineral reactions, fluid-rock interaction and element transport in metamorphic rocks on the trace element and isotopic composition of minerals, rocks and percolating fluids or melts can be predicted. One of the included publications shows that trace element growth zonations in metamorphic garnet porphyroblasts can be used to get crucial information about the reaction path of the investigated sample. In order to interpret the major and trace element distribution and zoning patterns in terms of the reaction history of the samples, we combined thermodynamic forward models with mass-balance rare earth element calculations. Such combined thermodynamic and mass-balance calculations of the rare earth element distribution among the modelled stable phases yielded characteristic zonation patterns in garnet that closely resemble those in the natural samples. We can show in that paper that garnet growth and trace element incorporation occurred in near thermodynamic equilibrium with matrix phases during subduction and that the rare earth element patterns in garnet exhibit distinct enrichment zones that fingerprint the minerals involved in the garnet-forming reactions. In two of the presented publications I illustrate the capacities of combined thermodynamic-geochemical modeling based on examples relevant to mass transfer in subduction zones. The first example focuses on fluid-rock interaction in and around a blueschist-facies shear zone in felsic gneisses, where fluid-induced mineral reactions and their effects on boron (B) concentrations and isotopic compositions in white mica are modeled. In the second example, fluid release from a subducted slab and associated transport of B and variations in B concentrations and isotopic compositions in liberated fluids and residual rocks are modeled. I show that, combined with experimental data on elemental partitioning and isotopic fractionation, thermodynamic forward modeling unfolds enormous capacities that are far from exhausted. In my publications presented in this Habilitationsschrift I compare the modeled results to geochemical data of natural minerals and rocks and demonstrate that the combination of thermodynamic and geochemical models enables quantification of metamorphic processes and insights into element cycling that would have been unattainable so far. Thus, the contributions to the science community presented in this Habilitatonsschrift concern the fields of petrology, geochemistry, geochronology but also ore geology that all use thermodynamic and geochemical models to solve various problems related to geo-materials.},
  language  = {en}
}
@phdthesis{Eugster2018,
  author    = {Eugster, Patricia},
  title     = {Landscape evolution in the western Indian Himalaya since the Miocene},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-420329},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XXI, 208},
  year      = {2018},
  abstract  = {The Himalayan arc stretches >2500 km from east to west at the southern edge of the Tibetan Plateau, representing one of the most important Cenozoic continent-continent collisional orogens. Internal deformation processes and climatic factors, which drive weathering, denudation, and transport, influence the growth and erosion of the orogen. During glacial times wet-based glaciers sculpted the mountain range and left overdeepend and U-shaped valleys, which were backfilled during interglacial times with paraglacial sediments over several cycles. These sediments partially still remain within the valleys because of insufficient evacuation capabilities into the foreland. Climatic processes overlay long-term tectonic processes responsible for uplift and exhumation caused by convergence. Possible processes accommodating convergence within the orogenic wedge along the main Himalayan faults, which divide the range into four major lithologic units, are debated. In this context, the identification of processes shaping the Earth's surface on short- and on long-term are crucial to understand the growth of the orogen and implications for landscape development in various sectors along the arc. This thesis focuses on both surface and tectonic processes that shape the landscape in the western Indian Himalaya since late Miocene. In my first study, I dated well-preserved glacially polished bedrock on high-elevated ridges and valley walls in the upper of the Chandra Valley the by means of 10Be terrestrial cosmogenic radionuclides (TCN). I used these ages and mapped glacial features to reconstruct the extent and timing of Pleistocene glaciation at the southern front of the Himalaya. I was able to reconstruct an extensive valley glacier of ~200 km length and >1000 m thickness. Deglaciation of the Chandra Valley glacier started subsequently to insolation increase on the Northern Hemisphere and thus responded to temperature increase. I showed that the timing this deglaciation onset was coeval with retreat of further midlatitude glaciers on the Northern and Southern Hemispheres. These comparisons also showed that the post-LGM deglaciation very rapid, occurred within a few thousand years, and was nearly finished prior to the B{\o}lling/Aller{\o}d interstadial. A second study (co-authorship) investigates how glacial advances and retreats in high mountain environments impact the landscape. By 10Be TCN dating and geomorphic mapping, we obtained maximal length and height of the Siachen Glacier within the Nubra Valley. Today the Shyok and Nubra confluence is backfilled with sedimentary deposits, which are attributed to the valley blocking of the Siachen Glacier 900 m above the present day river level. A glacial dam of the Siachen Glacier blocked the Shyok River and lead to the evolution of a more than 20 km long lake. Fluvial and lacustrine deposits in the valley document alternating draining and filling cycles of the lake dammed by the Siachen Glacier. In this study, we can show that glacial incision was outpacing fluvial incision. In the third study, which spans the million-year timescale, I focus on exhumation and erosion within the Chandra and Beas valleys. In this study the position and discussed possible reasons of rapidly exhuming rocks, several 100-km away from one of the main Himalayan faults (MFT) using Apatite Fission Track (AFT) thermochronometry. The newly gained AFT ages indicate rapid exhumation and confirm earlier studies in the Chandra Valley. I assume that the rapid exhumation is most likely related to uplift over subsurface structures. I tested this hypothesis by combining further low-temperature thermochronometers from areas east and west of my study area. By comparing two transects, each parallel to the Beas/Chandra Valley transect, I demonstrate similarities in the exhumation pattern to transects across the Sutlej region, and strong dissimilarities in the transect crossing the Dhauladar Range. I conclude that the belt of rapid exhumation terminates at the western end of the Kullu-Rampur window. Therewith, I corroborate earlier studies suggesting changes in exhumation behavior in the western Himalaya. Furthermore, I discussed several causes responsible for the pronounced change in exhumation patterns along strike: 1) the role of inherited pre-collisional features such as the Proterozoic sedimentary cover of the Indian basement, former ridges and geological structures, and 2) the variability of convergence rates along the Himalayan arc due to an increased oblique component towards the syntaxis. The combination of field observations (geological and geomorphological mapping) and methods to constrain short- and long-term processes (10Be, AFT) help to understand the role of the individual contributors to exhumation and erosion in the western Indian Himalaya. With the results of this thesis, I emphasize the importance of glacial and tectonic processes in shaping the landscape by driving exhumation and erosion in the studied areas.},
  language  = {en}
}
@phdthesis{Bergner2003,
  author    = {Bergner, Andreas G. N.},
  title     = {Lake-level fluctuations and Late Quaternary climate change in the Central Kenya Rift},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001428},
  school      = {Universit{\"a}t Potsdam},
  year      = {2003},
  abstract  = {Diese Arbeit besch{\"a}ftigt sich mit der Rekonstruktion von Klima in historischen Zeiten im tropischen Ostafrika. Nach einer {\"U}bersicht {\"u}ber die heutigen klimatischen Bedingungen der Tropen und den Besonderheiten des ostafrikanischen Klimas, werden die M{\"o}glichkeiten der Klimarekonstruktion anhand von Seesedimenten diskutiert. Es zeigt sich, dass die hoch gelegenen Seen des Zentralen Keniarifts, als Teil des Ostafrikanischen Grabensystems, besonders geeignete Klimaarchive darstellen, da sie sensibel auf klimatische Ver{\"a}nderungen reagieren. Ver{\"a}nderungen der Seechemie, wie sie in den Sedimenten aufgezeichnet werden, eignen sich um die nat{\"u}rlichen Schwankungen in der Quart{\"a}ren Klimageschichte Ostafrikas nachzuzeichnen. Basierend auf der guten 40Ar/39Ar- und 14C-Datierbarkeit der Seesedimente wird eine Chronologie der pal{\"a}o{\"o}kologischen Bedingungen anhand von Diatomeenvergesellschaftungen restauriert. Dabei zeigen sich f{\"u}r die Seen Nakuru, Elmenteita und Naivasha kurzfristige Transgression/ Regressions-Zyklen im Intervall von ca. 11.000 Jahren w{\"a}hrend des letzten (ca. 12.000 bis 6.000 J.v.H.) und vorletzten Interglazials (ca. 140.000 bis 60.000 J.v.H.). Zus{\"a}tzlich kann ein allgemeiner, langfristiger Trend der Seeentwicklung von großen Frischwasserseen hin zu st{\"a}rker salinen Gew{\"a}ssern innerhalb der letzen 1 Mio. Jahre festgestellt werden. Mittels Transferfunktionen und einem hydro-klimatischen Modellansatz k{\"o}nnen die restaurierten limnologischen Bedingungen als klimatische Schwankungen des Einzugsgebietes interpretiert werden. Wenngleich auch der zus{\"a}tzliche Einfluss von tektonischen Ver{\"a}nderungen auf das Seeeinzugsgebiet und das Gewicht ver{\"a}nderter Grundwasserstr{\"o}me abgewogen werden, zeigt sich, dass allein geringf{\"u}gig erh{\"o}hte Niederschlagswerte von ca. 30±10 \% zu dramatischen Seespiegelanstiegen im Zentralen Keniarift f{\"u}hren. Aufgrund der etablierten hydrrologisch-klimatischen Wechselwirkungen werden R{\"u}ckschl{\"u}sse auf die nat{\"u}rliche Variabilit{\"a}t des ostafrikanischen Klimas gezogen. Zudem wird die Sensitivit{\"a}t der Keniarift-Seen in Bezug auf die St{\"a}rke der {\"a}quatorialen Insolation und hinsichtilch variabler Oberfl{\"a}chenwassertemperaturen des Indischen Ozeans bewertet.},
  language  = {en}
}