TY - JOUR A1 - Mey, Jürgen A1 - Scherler, Dirk A1 - Wickert, Andrew D. A1 - Egholm, David L. A1 - Tesauro, Magdala A1 - Schildgen, Taylor F. A1 - Strecker, Manfred T1 - Glacial isostatic uplift of the European Alps JF - Nature Communications Y1 - 2016 U6 - https://doi.org/10.1038/ncomms13382 SN - 2041-1723 VL - 7 SP - 2357 EP - 2371 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Savi, Sara A1 - Schildgen, Taylor F. A1 - Tofelde, Stefanie A1 - Wittmann, Hella A1 - Scherler, Dirk A1 - Mey, Jürgen A1 - Alonso, Ricardo N. A1 - Strecker, Manfred T1 - Climatic controls on debris-flow activity and sediment aggradation: The Del Medio fan, NW Argentina JF - Journal of geophysical research : Earth surface N2 - In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between subhumid and arid climates and hosts the only active debris-flow fan within this intermontane valley. By combining Be-10 analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove aggradation in other nearby tributaries in the past. Y1 - 2016 U6 - https://doi.org/10.1002/2016JF003912 SN - 2169-9003 SN - 2169-9011 VL - 121 SP - 2424 EP - 2445 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mey, Jürgen A1 - Scherler, Dirk A1 - Zeilinger, Gerold A1 - Strecker, Manfred T1 - Estimating the fill thickness and bedrock topography in intermontane valleys using artificial neural networks JF - Journal of geophysical research : Earth surface N2 - Thick sedimentary fills in intermontane valleys are common in formerly glaciated mountain ranges but difficult to quantify. Yet knowledge of the fill thickness distribution could help to estimate sediment budgets of mountain belts and to decipher the role of stored material in modulating sediment flux from the orogen to the foreland. Here we present a new approach to estimate valley fill thickness and bedrock topography based on the geometric properties of a landscape using artificial neural networks. We test the potential of this approach following a four-tiered procedure. First, experiments with synthetic, idealized landscapes show that increasing variability in surface slopes requires successively more complex network configurations. Second, in experiments with artificially filled natural landscapes, we find that fill volumes can be estimated with an error below 20%. Third, in natural examples with valley fill surfaces that have steeply inclined slopes, such as the Unteraar and the Rhone Glaciers in the Swiss Alps, for example, the average deviation of cross-sectional area between the measured and the modeled valley fill is 26% and 27%, respectively. Finally, application of the method to the Rhone Valley, an overdeepened glacial valley in the Swiss Alps, yields a total estimated sediment volume of 9711km(3) and an average deviation of cross-sectional area between measurements and model estimates of 21.5%. Our new method allows for rapid assessment of sediment volumes in intermontane valleys while eliminating most of the subjectivity that is typically inherent in other methods where bedrock reconstructions are based on digital elevation models. KW - sediment storage KW - sediment thickness KW - intermontane valleys KW - geomorphometry KW - artificial neural networks Y1 - 2015 U6 - https://doi.org/10.1002/2014JF003270 SN - 2169-9003 SN - 2169-9011 VL - 120 IS - 7 SP - 1301 EP - 1320 PB - American Geophysical Union CY - Washington ER - TY - INPR A1 - Wang, Ping A1 - Scherler, Dirk A1 - Jing Liu-Zeng, A1 - Mey, Jürgen A1 - Avouac, Jean-Philippe A1 - Zhang, Yunda A1 - Shi, Dingguo T1 - GEOMORPHOLOGY Response to Comment on "Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet" T2 - Science N2 - In their Comment, Zeitler et al. do not challenge our results or interpretation. Our study does not disprove coupling between tectonic uplift and erosion but suggests that this coupling cannot be the sole explanation of rapid uplift in the Himalayan syntaxes. Y1 - 2015 SN - 0036-8075 SN - 1095-9203 VL - 349 IS - 6250 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Scherler, Dirk A1 - Munack, Henry A1 - Mey, Jürgen A1 - Eugster, Patricia A1 - Wittmann, Hella A1 - Codilean, Alexandru T. A1 - Kubik, Peter A1 - Strecker, Manfred T1 - Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau: A > 100 k.y. chronology from the Shyok Valley, Karakoram JF - Geological Society of America bulletin N2 - Some of the largest and most erosive floods on Earth result from the failure of glacial dams. While potentially cataclysmic ice dams are recognized to have repeatedly formed along ice-sheet margins, much less is known about the frequency and longevity of ice dams caused by mountain glaciers, and their impact on landscape evolution. Here we present field observations and results from cosmogenic nuclide dating that allow reconstructing a > 100-k.y.-long history of glacial damming in the Shyok Valley, eastern Karakoram (South Asia). Our field observations provide evidence that Asia's second-longest glacier, the Siachen, once extended for over 180 km and blocked the Shyok River during the penultimate glacial period, leading to upstream deposition of a more than 400-m-thick fluvio-lacustrine valley fill. Be-10-depth profile modeling indicates that glacial damming ended with the onset of the Eemian interglacial and that the Shyok River subsequently incised the valley fill at an average rate of similar to 4-7 m k.y.(-1). Comparison with contemporary ice-dammed lakes in the Karakoram and elsewhere suggests recurring outburst floods during the aggradation period, while over 25 cycles of fining-upward lake deposits within the valley fill indicate impounding of floods from farther upstream. Despite prolonged damming, the net effect of this and probably earlier damming episodes by the Siachen Glacier is dominated by glacial erosion in excess of fluvial incision, as evidenced by a pronounced overdeepening that follows the glaciated valley reach. Strikingly similar overdeepened valleys at all major confluences of the Shyok and Indus Rivers with Karakoram tributaries indicate that glacial dams and subsequent outburst floods have been widespread and frequent in this region during the Quaternary. Our study suggests that the interaction of Karakoram glaciers with the Shyok and Indus Rivers promoted valley incision and headward erosion into the western margin of the Tibetan Plateau. Y1 - 2014 U6 - https://doi.org/10.1130/B30942.1 SN - 0016-7606 SN - 1943-2674 VL - 126 IS - 5-6 SP - 738 EP - 758 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Wang, Ping A1 - Scherler, Dirk A1 - Jing Liu-Zeng, A1 - Mey, Jürgen A1 - Avouac, Jean-Philippe A1 - Zhang, Yunda A1 - Shi, Dingguo T1 - Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet JF - Science N2 - The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay between river incision and rock uplift is important for understanding tectonic deformation in this region. We report here the discovery of a deeply incised canyon of the Yarlung Tsangpo River, at the eastern end of the Himalaya, which is now buried under more than 500 meters of sediments. By reconstructing the former valley bottom and dating sediments at the base of the valley fill, we show that steepening of the Tsangpo Gorge started at about 2 million to 2.5 million years ago as a consequence of an increase in rock uplift rates. The high erosion rates within the gorge are therefore a direct consequence of rapid rock uplift. Y1 - 2014 U6 - https://doi.org/10.1126/science.1259041 SN - 0036-8075 SN - 1095-9203 VL - 346 IS - 6212 SP - 978 EP - 981 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - THES A1 - Mey, Jürgen T1 - Intermontane valley fills T1 - Intermontane Talverfüllungen BT - recorders of climate, tectonics and landscape evolution BT - Zeugen von Klima, Tektonik und Landschaftsentwicklung N2 - Sedimentary valley fills are a widespread characteristic of mountain belts around the world. They transiently store material over time spans ranging from thousands to millions of years and therefore play an important role in modulating the sediment flux from the orogen to the foreland and to oceanic depocenters. In most cases, their formation can be attributed to specific fluvial conditions, which are closely related to climatic and tectonic processes. Hence, valley-fill deposits constitute valuable archives that offer fundamental insight into landscape evolution, and their study may help to assess the impact of future climate change on sediment dynamics. In this thesis I analyzed intermontane valley-fill deposits to constrain different aspects of the climatic and tectonic history of mountain belts over multiple timescales. First, I developed a method to estimate the thickness distribution of valley fills using artificial neural networks (ANNs). Based on the assumption of geometrical similarity between exposed and buried parts of the landscape, this novel and highly automated technique allows reconstructing fill thickness and bedrock topography on the scale of catchments to entire mountain belts. Second, I used the new method for estimating the spatial distribution of post-glacial sediments that are stored in the entire European Alps. A comparison with data from exploratory drillings and from geophysical surveys revealed that the model reproduces the measurements with a root mean squared error (RMSE) of 70m and a coefficient of determination (R2) of 0.81. I used the derived sediment thickness estimates in combination with a model of the Last Glacial Maximum (LGM) icecap to infer the lithospheric response to deglaciation, erosion and deposition, and deduce their relative contribution to the present-day rock-uplift rate. For a range of different lithospheric and upper mantle-material properties, the results suggest that the long-wavelength uplift signal can be explained by glacial isostatic adjustment with a small erosional contribution and a substantial but localized tectonic component exceeding 50% in parts of the Eastern Alps and in the Swiss Rhône Valley. Furthermore, this study reveals the particular importance of deconvolving the potential components of rock uplift when interpreting recent movements along active orogens and how this can be used to constrain physical properties of the Earth’s interior. In a third study, I used the ANN approach to estimate the sediment thickness of alluviated reaches of the Yarlung Tsangpo River, upstream of the rapidly uplifting Namche Barwa massif. This allowed my colleagues and me to reconstruct the ancient river profile of the Yarlung Tsangpo, and to show that in the past, the river had already been deeply incised into the eastern margin of the Tibetan Plateau. Dating of basal sediments from drill cores that reached the paleo-river bed to 2–2.5 Ma are consistent with mineral cooling ages from the Namche Barwa massif, which indicate initiation of rapid uplift at ~4 Ma. Hence, formation of the Tsangpo gorge and aggradation of the voluminous valley fill was most probably a consequence of rapid uplift of the Namche Barwa massif and thus tectonic activity. The fourth and last study focuses on the interaction of fluvial and glacial processes at the southeastern edge of the Karakoram. Paleo-ice-extent indicators and remnants of a more than 400-m-thick fluvio-lacustrine valley fill point to blockage of the Shyok River, a main tributary of the upper Indus, by the Siachen Glacier, which is the largest glacier in the Karakoram Range. Field observations and 10Be exposure dating attest to a period of recurring lake formation and outburst flooding during the penultimate glaciation prior to ~110 ka. The interaction of Rivers and Glaciers all along the Karakorum is considered a key factor in landscape evolution and presumably promoted headward erosion of the Indus-Shyok drainage system into the western margin of the Tibetan Plateau. The results of this thesis highlight the strong influence of glaciation and tectonics on valley-fill formation and how this has affected the evolution of different mountain belts. In the Alps valley-fill deposition influenced the magnitude and pattern of rock uplift since ice retreat approximately 17,000 years ago. Conversely, the analyzed valley fills in the Himalaya are much older and reflect environmental conditions that prevailed at ~110 ka and ~2.5 Ma, respectively. Thus, the newly developed method has proven useful for inferring the role of sedimentary valley-fill deposits in landscape evolution on timescales ranging from 1,000 to 10,000,000 years. N2 - Sedimentäre Talverfüllungen sind ein häufiges Merkmal von Gebirgen auf der ganzen Welt. Sie speichern Abtragungsprodukte über Zeiträume von Tausenden bis Millionen von Jahren und beeinflussen den Sedimenttransport vom Gebirge in das Vorland und in die ozeanischen Becken. Die Bildung solcher Sedimentspeicher geht oft auf Zustände im fluvialen System zurück, welche mit bestimmten klimatischen und tektonischen Prozessen in Verbindung gebracht werden können. Talverfüllungen stellen daher wertvolle Archive dar, die über fundamentale Zusammenhänge in der Landschaftsgenese Aufschluss geben und deren Untersuchung dazu beiträgt, die Auswirkungen des Klimawandels auf die Sedimentdynamik im Gebirge zu prognostizieren. In dieser Arbeit untersuchte ich intermontane Talverfüllungen, um die klimatische und tektonische Geschichte von Gebirgszügen über mehrere Zeitskalen hinweg zu ermitteln. Zuerst entwickelte ich eine Methode zur Abschätzung von Sedimentmächtigkeiten mit Hilfe von künstlichen neuralen Netzen, die auf der Annahme basiert, dass sich die zugeschütteten und die freiliegenden Bereiche der Landschaft geometrisch ähneln. Diese neuartige und hochautomatisierte Methode macht es möglich, Sedimentmächtigkeiten und Untergrundtopographien für einzelne Einzugsgebiete bis hin zu ganzen Gebirgen abzuschätzen. Als zweites benutzte ich die neue Methode, um die Mächtigkeitsverteilung der postglazialen Sedimentspeicher in den Europäischen Alpen zu rekonstruieren. Ein Vergleich mit Daten aus Bohrlochmessungen und geophysikalischen Explorationen zeigte, dass das Modell die gemessenen Mächtigkeiten mit einem quadratischen Mittelwert des Fehlers (RMSE) von 70m und einem Bestimmtheitsmaß (R2) von 0.81 reproduziert. Ich verwendete diese Sedimentverteilung in Kombination mit einem Modell der alpinen Eiskappe des letzten glazialen Maximums (LGM), um die Reaktion der Lithosphäre auf Abschmelzen, Erosion und Ablagerung zu berechnen und deren Beiträge zur derzeitigen Gesteinshebung abzuleiten. Unter Berücksichtigung einer Reihe verschiedener Eigenschaften der Lithosphäre und des oberen Erdmantels zeigten die Resultate, dass das langwellige Hebungsmuster im Wesentlichen durch Glazialisostasie erklärt werden kann und dass die Entlastung durch Erosion eine untergeordnete Rolle spielt. Darüber hinaus postulierte ich eine tektonische Komponente von über 50% in Teilen der Ostalpen und im Schweizer Rhône Tal. Die Studie verdeutlicht, dass die Entflechtung der Prozesse, die zur Gesteinshebung beitragen, eine entscheidende Rolle spielt bei der Interpretation rezenter Bewegungen entlang aktiver Orogene und bei der Abschätzung von physikalischen Eigenschaften des Erdinneren. Im dritten Teil berechnete ich die Mächtigkeitsverteilung der sedimentären Talverfüllung des Yarlung Tsangpo Tales oberhalb des Namche Barwa Massivs am östlichen Rand des Tibet Plateaus. Dies ermöglichte meinen Kollegen und mir das ehemalige Flusslängsprofil zu rekonstruieren und zu zeigen, dass sich der Yarlung Tsangpo in der Vergangenheit bereits tief in den östlichen Rand des Tibet Plateaus einschnitt. Die Basis der Sedimente wurde erbohrt und beprobt und deren Ablagerung auf 2–2.5 Ma datiert was konsistent mit Abkühlungsaltern von Mineralen des Namche Barwa Massivs ist, die auf den Beginn einer beschleunigten Hebung vor ~4 Ma hindeuten. Dies führte zu der Schlussfolgerung, dass die Bildung der Tsangpo Schlucht und die Aggradation der Talsedimente höchstwahrscheinlich in Folge der schnellen Hebung des Namche Barwa Massivs geschah, welche letztendlich auf tektonische Aktivität zurück geht. Der vierte und letzte Teil behandelt die Interaktion fluvialer und glazialer Prozesse am südöstlichen Rand des Karakorums. Indikatoren für die frühere Eisausdehnung und die Überreste einer bis zu 400m mächtigen fluvio-lakustrinen Talverfüllung weisen auf eine Blockade des Shyok, eines Hauptzuflusses es Oberen Indus, durch den Siachen Gletscher, den größten Gletscher des Karakorums, hin. Weitere Geländebefunde und Oberflächendatierungen mittels kosmogenem 10Be bezeugen, dass es während des vorletzten Glaziales zu einem mehrfachen Aufstauen des Shyok und damit assoziierten Seeausbrüchen gekommen ist. Das Zusammenwirken von Flüssen und Gletschern entlang des Karakorums war maßgeblich für die Landschaftsentwicklung und führte möglicherweise zum Einschneiden von Tälern in den westlichen Rand des Tibet Plateaus. Die vorliegende Arbeit unterstreicht die Bedeutung von Vergletscherung und Tektonik bei der Bildung von intermontanen Sedimentspeichern und deren Einwirken auf die Entwicklung zweier Gebirge. In den Alpen beeinflusst die Ablagerung von Talfüllungen die Raten und das Muster der Gesteinshebung seit Rückzug des Eises vor ca. 17,000 Jahren. Demgegenüber sind die in dieser Arbeit betrachteten Talfüllungen des Himalayas weit älter und geben Aufschluss über die Umweltbedingungen vor jeweils 110 ka und 2.5 Ma. Es zeigt sich, dass die neue Methode zur Abschätzung von Mächtigkeiten und Volumina intermontaner Talverfüllungen dazu beiträgt, die Landschaftsentwicklung über Zeiträume von 1,000 bis 10,000,000 Jahren zu rekonstruieren. KW - intermontane valley fill KW - sediment thickness KW - bedrock elevation KW - artificial neural networks KW - sediment volume KW - landscape evolution KW - glacial isostatic adjustment KW - isostatic uplift KW - LGM KW - Ice model KW - European Alps KW - outburst floods KW - glacial incision KW - Tibetan Plateau KW - Shyok River KW - cosmogenic nuclides KW - exposure age dating KW - ice dam KW - Karakoram KW - Namche Barwa KW - Yarlung-Tsangpo Gorge KW - burial dating KW - tectonic uplift KW - syntaxis KW - intermontane Talverfüllungen KW - Sedimentmächtigkeit KW - Grundgesteinshöhe KW - künstliche neurale Netzwerke KW - Sedimentvolumen KW - Landschaftsentwicklung KW - Glazialisostasie KW - isostatische Hebung KW - LGM KW - Eismodell KW - Europäische Alpen KW - Seeausbrüche KW - glaziale Einschneidung KW - Tibet Plateau KW - Shyok Fluss KW - kosmogene Nuklide KW - Expositionsaltersdatierung KW - Eisdamm KW - Karakorum KW - Namche Barwa KW - Yarlung-Tsangpo Schlucht KW - Verschüttungsaltersdatierung KW - tektonische Hebung KW - Syntaxe Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-103158 ER -