Publikationen - Lehrstuhl für Geomorphologie

Expanding the Late Quaternary morphochronology of Atacama’s coastal alluvial fans by Schmidt hammer exposure dating reveals spatially distinct genesis. Walk, Janek. In Quaternary Science Advances, 21, S. 100305. Elsevier BV, 2026.

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Late Quaternary alluvial fans along the coast of the hyperarid Atacama Desert have been exploited as palaeoenvironmental archives by several studies. However, a regional palaeoenvironmental interpretation remains challenging as established geochronological frameworks are based on a limited number of sites where fan aggradation was constrained by numerical dating. Consequently, it is unclear to what extent fan aggradation and progradation is controlled by large-scale allogenic versus individual autogenic forcing. To therefore expand the regional alluvial fan morphochronology along the south-central coast, the applicability of cost-effective Schmidt hammer exposure dating (SHD) was explored on boulders of plutonic lithology. The independently exposure-dated coastal alluvial fan (CAF) Paposo served as regional age-calibration site for SHD of 11 telescopic CAFs between 24.25°S and 25.25°S. SHD was complemented by the assessment of the CAFs’ terrestrial and shelf morphometry and the hydromorphometric and climatic catchment properties. The results of the successfully calibrated SHD suggest that weathering in the coastal desert allows for age ranges extending over the Late Quaternary. The expanded morphochronology reveals a distinct fan evolution segmenting a synchronous morphogenesis south of 24.85°S from a diachronous one in the north. Spatial segmentation is reflected in specific catchment hydromorphometric characteristics and differences in the relationships between terrestrial fan versus shelf gradients – the latter indicating a dominant allogenic control of eustatic sea-level changes at least in the south. While spatiotemporal variability in Late Quaternary precipitation and tectonic activity may constitute additional relevant factors, diachronism of northern CAF evolution could also be the response to individual autogenic fan dynamics.

Dynamics of dunes and climate variability over the last five decades: A remote sensing analysis of regional contrasts on the northeastern Tibetan Plateau and the adjacent Hexi Corridor. Dörwald, Lukas; Lehmkuhl, Frank; Delobel, Lucie; Yang, Xiaoping; Stauch, Georg. In Global and Planetary Change, 252, S. 104873. Elsevier BV, 2025.

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Dunes react quickly to climatic changes, with the main drivers being the dominating wind regime (e.g. magnitude and direction), precipitation, and temperature. Furthermore, human impact can alter dune movement by fixation of active dunes through greening projects, or reactivation of fixed dunes through overgrazing or neglect of former human structures. The northeastern Tibetan Plateau shows a high variability of climatic pa- rameters like wind, temperature, and precipitation within a high elevation environment, situated between the mid-latitude westerlies and the East Asian Summer monsoon. This study assesses changes in the movement of active barchans and sand sheets in three different regions of the northeastern Tibetan Plateau and additionally the adjacent Hexi Corridor to evaluate the different impact of climate change and anthropogenic activities in the past 54 years. Over 500 active barchan dunes and 46 sand sheets were studied to assess climatic influence on aeolian deposits. Since weather stations on the Tibetan Plateau are rare and their measurements often cover only a short time span, ERA-5 reanalysis data was utilized. Dune migration rates were deduced from different satellite imagery taken from 1968 onwards. The Normalized Difference Vegetation Index was implemented to observe changes in vegetation. As a further metric, dune field density changes were calculated, to investigate dynamics in dune field settings and human impact from agriculture in the Hexi Corridor. The results show similar migration rates in the Hexi Corridor and the Gonghe Basin with mean values of 8.54 and 7.33 m y 1, respectively, while in the Source Area of the Yellow River the dunes are migrating slower with a mean of 3.62 m y 1. The Zoige Basin sand sheets show mostly an expansion in size with a mean growth of 65.39 km2 y 1 and a sum extension of 3007.95 km2 since 1968. The results show the influence of the East Asian Summer Monsoon as a driver for precipitation and subsequent vegetation establishment altering dune movement through fixation. Furthermore, regional dune behavior is influenced by human activities during the past decades, diverting the climatic signal.

Late Quaternary geomorphological processes and landscape evolution in the Khur Basin, central Iran. Rashidi Koochi, Z.; Büdel, C.; Walk, J.; Fuchs, M.; Torabi, M.; Karimi, A.; Baumhauer, R.; Stauch, G. In E&G Quaternary Science Journal, 74(2), S. 193–212. 2025.

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The interior of the Central Iranian Plateau is an important area for the study of the palaeoenvironmental controls of early human dispersal in arid regions. In the now hyper-arid region, human migrations may have been affected by the major Quaternary climatic changes. However, due to the difficult access and harsh climate in the central desert, there are scarce palaeoenvironmental data available to reconstruct the interplay between migration of past cultures and environmental change. In the Khur Basin, located in the central part of the Iranian Plateau and on the eastern edge of the central Great Kavir, geomorphological landscape archives have been preserved that provide valuable information about the landscape evolution and climate dynamics of this characteristic desert region. As the spatiotemporal relationships between the dominant geomorphological forms and processes in this area have mostly been studied in isolation, this study adopted an integrative approach to better assess the diverse interactions. This involved geomorphological mapping and detailed field-based geomorphological and stratigraphical analyses of 12 sedimentary sequences distributed over eight geomorphic units of the Khur Basin. The resulting relative chronological classification of the morphostratigraphy suggests a logical sequence of six main phases of landscape evolution. By combining our mapping results with dated geoarchives of the region, a tentative chronology was developed. The early stages as observed in the stratigraphically oldest preserved landforms were characterised by a sequence of different processes, including pediment erosion, alluvial fan and dune formation, and soil development, and probably date to the phase before and during Marine Isotope Stage (MIS) 3. The subsequent landforms and deposits are to be interpreted as a result of alluvial fan progradation into the basin interior as well as dune development, which are probably attributable to the cold and arid conditions during the Last Glacial Maximum (LGM). The most recent morphostratigraphic findings correlate with the combined effects of pedological and geomorphological processes, including the formation of gypsum-rich soils, sand dune reactivation, and the deflation of playa surfaces. These findings indicate an increasing aridity in the area, which is often associated with the climatic development of the Holocene. Through the systematic integration of stratigraphical and geomorphological evidence, this study provides a first comprehensive historical–genetic model of landscape evolution in the Khur Basin.

Drivers of late Quaternary lake level fluctuations of Khyargas Nuur, western Mongolia - glacial meltwater discharge or atmospheric moisture supply?. Wolf, Dennis; Lehmkuhl, Frank; Schaubert, Viktor; Rahimzadeh, Neda; Frechen, Manfred; Stauch, Georg; Batkhishig, Ochirbat; Wegmann, Karl. In Quaternary Science Reviews, 359, S. 109373. 2025.

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This study presents the first comprehensive late Quaternary chronology of lake level variations of the Khyargas Nuur (western Mongolia), based on a geomorphological approach supported by luminescence dating of relict shorelines and lacustrine sediments. The endorheic Khyargas Nuur in the Basin of Great Lakes is the ultimate sink of a sequential water and sediment cascade from the adjacent Mongolian Altai and Khangai Mountains. Several intercalated lakes repeatedly joined as one major paleolake, as evidenced by various morphological shoreline features. Situated in the mid-latitude Westerlies-dominated climate regime of Arid Central Asia and affected by the distant effects of the East Asian Summer Monsoon, the dynamic climate of the Basin of Great Lakes is determined by the co-evolution of these atmospheric circulation systems. Our observations comprise 11 distinct paleolake levels between +7 m and +188 m above modern lake level (aml). Calculations of paleolake extent and water volume emphasize the periodically enhanced inflow and gradual capture and abandonment of upstream-located lakes. In the regional to global paleoclimatic context, our results reveal three distinct phases of lake level dynamics: (i) A transgression to a maximum level of +129 m aml during Marine Isotope Stage 5c (104.7 ± 14.4–88.8 ± 12.7 ka) primarily controlled by increased atmospheric moisture supply from the Westerlies. (ii) A post-Last Glacial Maximum lake expansion to a level of +118 m aml around 14 ka, ultimately controlled by enhanced glacial meltwater discharge into the basin. This is followed by a lake regression throughout the late Glacial to early Holocene transition in response to a gradually decreasing meltwater supply and a drier climate. (iii) A late Holocene transgression to +15 m aml reflecting a general Holocene wetting trend across arid Central Asia, followed by small-scale level fluctuations post 2.6 ka.

Late Quaternary geomorphological processes and landscape evolution in the Khur Basin, central Iran. Rashidi Koochi, Z.; Büdel, C.; Walk, J.; Fuchs, M.; Torabi, M.; Karimi, A.; Baumhauer, R.; Stauch, G. In E&G Quaternary Science Journal, 74(2), S. 193–212. 2025.

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The interior of the Central Iranian Plateau is an important area for the study of the palaeoenvironmental controls of early human dispersal in arid regions. In the now hyper-arid region, human migrations may have been affected by the major Quaternary climatic changes. However, due to the difficult access and harsh climate in the central desert, there are scarce palaeoenvironmental data available to reconstruct the interplay between migration of past cultures and environmental change. In the Khur Basin, located in the central part of the Iranian Plateau and on the eastern edge of the central Great Kavir, geomorphological landscape archives have been preserved that provide valuable information about the landscape evolution and climate dynamics of this characteristic desert region. As the spatiotemporal relationships between the dominant geomorphological forms and processes in this area have mostly been studied in isolation, this study adopted an integrative approach to better assess the diverse interactions. This involved geomorphological mapping and detailed field-based geomorphological and stratigraphical analyses of 12 sedimentary sequences distributed over eight geomorphic units of the Khur Basin. The resulting relative chronological classification of the morphostratigraphy suggests a logical sequence of six main phases of landscape evolution. By combining our mapping results with dated geoarchives of the region, a tentative chronology was developed. The early stages as observed in the stratigraphically oldest preserved landforms were characterised by a sequence of different processes, including pediment erosion, alluvial fan and dune formation, and soil development, and probably date to the phase before and during Marine Isotope Stage (MIS) 3. The subsequent landforms and deposits are to be interpreted as a result of alluvial fan progradation into the basin interior as well as dune development, which are probably attributable to the cold and arid conditions during the Last Glacial Maximum (LGM). The most recent morphostratigraphic findings correlate with the combined effects of pedological and geomorphological processes, including the formation of gypsum-rich soils, sand dune reactivation, and the deflation of playa surfaces. These findings indicate an increasing aridity in the area, which is often associated with the climatic development of the Holocene. Through the systematic integration of stratigraphical and geomorphological evidence, this study provides a first comprehensive historical–genetic model of landscape evolution in the Khur Basin.

Improved chronological constraints for Holocene rock glacier activity in the Ben Ohau Range, Southern Alps/New Zealand. Winkler, Stefan. In The Holocene, 35(3), S. 352–372. SAGE Publications, 2024.

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Investigation of the 2010 rock avalanche onto the regenerated glacier Brenndalsbreen, Norway. Engen, Siri H.; Gjerde, Marthe; Scheiber, Thomas; Seier, Gernot; Elvehoy, Hallgeir; Abermann, Jakob; Nesje, Atle; Winkler, Stefan; Haualand, Kristine F.; Rüther, Denise C.; Maschler, Alexander; Robson, Benjamin A.; Yde, Jacob C. In Landslides, 21(9), S. 2051–2072. 2024.

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Rock avalanches onto glaciers are rare in Norway. Here, we examine a rock avalanche that spread onto the regenerated Brenndalsbreen, an outlet glacier from Jostedalsbreen ice cap. The rock avalanche is intriguing in that limited information exists with respect to the exact time of failure, location of detachment area, and preparatory and triggering processes. Based on an analysis of ice stratigraphy and photographic documentation, we assess that the event happened between mid-March and June 4, 2010. A potential triggering factor could have been heavy snow and rainfall combined with above freezing air temperatures on March 18--19, 2010. We use digital terrain models to determine that the detachment area is at an almost vertical rock slope in a narrow gorge above Lower Brenndalsbreen. The deposit volume is estimated to 0.130\thinspace\textpm}{thinspace0.065 Mm3, and the H/L ratio and fahrböschung are 0.45 and 24textdegree, respectively. We apply a Voellmy flow model to confirm the detachment location and volume estimate by producing realistic runout lengths. Although glacial debuttressing may have been a likely preparatory process, the detachment area was exposed for 45--70 years before the rock avalanche occurred. The supraglacial rock avalanche debris was separated into two branches with a distinct melt-out line across the glacier. The debris reached the glacier front in 2019 and 2020, where it started being deposited proglacially while Lower Brenndalsbreen kept receding. The 2010 Brenndalsbreen rock avalanche may not be a unique event, as deposits constituting evidence of an old rock avalanche are currently melting out at the glacier front.

Implications of an Early Holocene climax in solifluction and related periglacial activity on Juvflye, Jotunheimen (southern Norway), as revealed by Schmidt-hammer exposure-age dating. Winkler, Stefan; Beylich, Achim A.; Laute, Katja; Matthews, John A.; Mourne, Richard W.; Wilson, Peter. In Geomorphology, 458, S. 109247. Elsevier BV, 2024.

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115 years of sediment deposition in a reservoir in Central Europe: Effects of the industrial history and environmental protection on heavy metals and microplastic. Stauch, Georg; Schulte, Philipp; Schwanen, Christina; Kümmerle, Eberhard Andreas; Dörwald, Lukas; Esch, Alexander; Lehmkuhl, Frank; Walk, Janek. In Earth Surface Processes and Landforms, 49(11), S. 3419–3436. Wiley, 2024.

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Humans have considerably influenced accumulation rates and sediment composition in lake deposits. Due to near-continuous accumulation, lakes and reservoirs are an excellent archive of these anthropogenic influences. The Urft Reservoir in the Eifel Mountains, western Germany, provides a unique record of the human influence on the landscape for the past 115 years. In 2020 and 2021, 24 cores and 23 surface samples were obtained from the bottom of the, by that time drained, reservoir. Grain size, heavy metals, weathering signatures and microplastic were analysed. For the chronology, caesium-137 and microplastic were used. Using the first occurrence of microplastic as well as different plastic types for dating was not successful. However, a distinct layer with a high number of microplastic particles could be traced back to a fire in 1991 and was used as an additional stratigraphic marker in the age-depth model. A period of relatively high accumulation rates in the reservoir occurred in the mid-1950s and was related to enhanced construction works in the local valleys. Analysis of heavy metal content in the reservoir sediments shows a strong connection to historical changes in ore industry in the valley of the Urft. Stricter environmental protection laws and the decline of the metal processing industry resulted in a reduced input of lead, copper and zinc in the reservoir until the mid-1980s. Since then, heavy metal content has remained relatively constant. A major flooding event in July 2021 did not lead to the remobilisation of older contaminated deposits as indicated by low heavy metal content in flood deposits. Accordingly, also the microplastic content is not increasing following the extreme event. Due to the degree of weathering of the flood deposits, it is argued that mainly hillslope material was transported into the Urft and subsequently into the Urft Reservoir during this event.

Schmidt-hammer R-values from glacially-scoured bedrock surfaces across glacier-foreland boundaries: Insights into Holocene weathering rates with implications for exposure-age dating. Matthews, John A.; Mourne, Richard W.; Wilson, Peter; Hill, Jennifer L.; Robbins, Celia; Winkler, Stefan. In Geomorphology, 454, S. 109139. Elsevier BV, 2024.

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115 years of sediment deposition in a reservoir in Central Europe: Effects of the industrial history and environmental protection on heavy metals and microplastic. Stauch, Georg; Schulte, Philipp; Schwanen, Christina; Kümmerle, Eberhard Andreas; Dörwald, Lukas; Esch, Alexander; Lehmkuhl, Frank; Walk, Janek. In Earth Surface Processes and Landforms. Wiley, 2024.

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Reconstruction of the pollution history of the Urft reservoir: an organic-geochemical investigation. Schwanen, Christina A.; Stauch, Georg; Schulte, Philipp; Schwarzbauer, Jan. In Environmental Sciences Europe, 36(1). Springer Science and Business Media LLC, 2024.

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115 years of sediment deposition in a reservoir in Central Europe: Topographic change detection. Stauch, Georg; Dörwald, Lukas; Esch, Alexander; Walk, Janek. In Earth Surface Processes and Landforms, 49(2), S. 582–600. 2024.

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Reservoirs have become an important component in the worldwide river sediment flux. Reservoirs prevent downstream sediment transport and have become a major sediment sink. In this study, sediment deposition during the last 115 years in the Urft Reservoir in western Germany is reconstructed. The Urft Reservoir is the oldest reservoir in the Eifel Mountains and was almost completely drained in 2020. This enabled a detailed mapping of the lake bottom using an unmanned aerial system and the computation of a high-resolution digital surface model. Topographic maps with a nominal resolution of 1:1000 from the time prior to the construction of the dam (around 1900) were used to construct a pre-reservoir elevation model. A digital elevation model of difference (DoD) was calculated from these two datasets for the reservoir floor (0.72 km2). Based on the DoD, a net sediment accumulation of 1.16 × 106 m3 was calculated alongside a propagated volume error of 6.91 × 105 m3, resulting in a mean accumulation of 1.54 m. Conservative vertical error propagation results in an average level of detection (LoD) of 1.8 m. In contrast, the comparison of the DoD with 47 cores in the upper part of the reservoir showed a mean difference of −0.11 m, indicating a high, independently assessed accuracy of the DoD. Three depositional hotspots were identified in the reservoir. One is close to the Urft dam where very fine sediments are draped across the pre-reservoir topography. Two areas are related to reservoir management. Sediment deposition in the Urft Reservoir has been comparably low in comparison to other regions globally, resulting in a 3.25% ± 1.93% loss of reservoir volume between 1905 and 2020. To analyse the effect of strong flooding events, a subset of the reservoir was analysed after an extreme event in July 2021, but accumulation did almost entirely not exceed the LoD.

Fog controls biological cycling of soil phosphorus in the Coastal Cordillera of the Atacama Desert. Sun, Xiaolei; Amelung, Wulf; Klumpp, Erwin; Walk, Janek; Mörchen, Ramona; Böhm, Christoph; Moradi, Ghazal; May, Simon Matthias; Tamburini, Federica; Wang, Ye; Bol, Roland. In Global Change Biology, 30(1). Wiley, 2024.

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Soils in hyper-arid climates, such as the Chilean Atacama Desert, show indications of past and present forms of life despite extreme water limitations. We hypothesize that fog plays a key role in sustaining life. In particular, we assume that fog water is incorporated into soil nutrient cycles, with the inland limit of fog penetration corresponding to the threshold for biological cycling of soil phosphorus (P). We collected topsoil samples (0–10 cm) from each of 54 subsites, including sites in direct adjacency (<10 cm) and in 1 m distance to plants, along an aridity gradient across the Coastal Cordillera. Satellite-based fog detection revealed that Pacific fog penetrates up to 10 km inland, while inland sites at 10–23 km from the coast rely solely on sporadic rainfall for water supply. To assess biological P cycling we performed sequential P fractionation and determined oxygen isotope of HCl-extractable inorganic δ. Total P (Pt) concentration exponentially increased from 336 mg kg−1 to a maximum of 1021 mg kg−1 in inland areas ≥10 km. With increasing distance from the coast, soil δ values declined exponentially from 16.6‰ to a constant 9.9‰ for locations ≥10 km inland. Biological cycling of HCl-Pi near the coast reached a maximum of 76%–100%, which could only be explained by the fact that fog water predominately drives biological P cycling. In inland regions, with minimal rainfall (<5 mm) as single water source, only 24 ± 14% of HCl-Pi was biologically cycled. We conclude that biological P cycling in the hyper-arid Atacama Desert is not exclusively but mainly mediated by fog, which thus controls apatite dissolution rates and related occurrence and spread of microbial life in this extreme environment.

Opportunities for international cooperation in the field of Disaster Risk and Resilience Research. Fekete, Alexander; Priesmeier, Peter; Büdel, Christian; Flörchinger, Verena; Heyn, Timo; Knoche, Luisa; Krippner, Nils; Stauch, Georg; Winkhardt-Enz, Ronja. 2024.

Fernerkundung und Cloud-Computing – Eine kurze Einführung. Stauch, Georg. In Angewandte Fernerkundung mit der Google Earth Engine / mit Beiträgen von: Eileen Berg [und 7 anderen] ; Hrsg.: Georg Stauch, S. 1–7. Geographisches Institut der RWTH Aachen, Aachen, 2024.

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Angewandte Fernerkundung mit der Google Earth Engine. Stauch, Georg. S. III, 120 S. : Illustrationen, Tabellen, Diagramme. Geographisches Institut der RWTH Aachen, Aachen, 2024.

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Dune behavior in the Source Area of the Yellow River under climate changes observed from various remote sensing datasets. Dörwald, Lukas; Lehmkuhl, Frank; Delobel, Lucie; Zhang, Deguo; Yang, Xiaoping; Stauch, Georg. In Aeolian Research, 67-69, S. 100928. 2024.

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Sand dunes are a landscape feature with a quick response time to climate change and human influences (e.g. grazing, greening projects, and fixation structures). Their migration rates and their development can help to gather information about changing environmental conditions over time. The Source Area of the Yellow River (SAYR), located upon the Tibetan Plateau, is highly complex with topographical, hydrological, and climatological influences on active dunes, making it a good study area for these interactions. Based on remote sensing datasets, spanning the last 54 years, 415 dunes were mapped for migration rate calculations. Further, climate data from ERA-5 reanalysis and a local climate station was used to assess their changes within a changing climate. Generally, dune migration rates are rather slow with an average of 3.62 m y-1. In accordance, the averaged resultant drift potential (RDP) values are lower than 10 m3/s−3(−|-). Further, we assessed the density development of the main active barchan dune field in direct premise of the Yellow River. Throughout the past 54 years, we observed the emergence of more than 5 new barchans per square kilometer. This increase is likely attributed to higher sand flux from the Yellow River, which has resulted from increased discharge due to declining snowfall and rising precipitation levels.

115 years of sediment deposition in a reservoir in Central Europe: Topographic change detection. Stauch, Georg; Dörwald, Lukas; Esch, Alexander; Walk, Janek. In Earth Surface Processes and Landforms, 49(2), S. 582–600. Wiley, 2024.

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Reservoirs have become an important component in the worldwide river sediment flux. Reservoirs prevent downstream sediment transport and have become a major sediment sink. In this study, sediment deposition during the last 115 years in the Urft Reservoir in western Germany is reconstructed. The Urft Reservoir is the oldest reservoir in the Eifel Mountains and was almost completely drained in 2020. This enabled a detailed mapping of the lake bottom using an unmanned aerial system and the computation of a high-resolution digital surface model. Topographic maps with a nominal resolution of 1:1000 from the time prior to the construction of the dam (around 1900) were used to construct a pre-reservoir elevation model. A digital elevation model of difference (DoD) was calculated from these two datasets for the reservoir floor (0.72 km2). Based on the DoD, a net sediment accumulation of 1.16 × 106 m3 was calculated alongside a propagated volume error of 6.91 × 105 m3, resulting in a mean accumulation of 1.54 m. Conservative vertical error propagation results in an average level of detection (LoD) of 1.8 m. In contrast, the comparison of the DoD with 47 cores in the upper part of the reservoir showed a mean difference of −0.11 m, indicating a high, independently assessed accuracy of the DoD. Three depositional hotspots were identified in the reservoir. One is close to the Urft dam where very fine sediments are draped across the pre-reservoir topography. Two areas are related to reservoir management. Sediment deposition in the Urft Reservoir has been comparably low in comparison to other regions globally, resulting in a 3.25% ± 1.93% loss of reservoir volume between 1905 and 2020. To analyse the effect of strong flooding events, a subset of the reservoir was analysed after an extreme event in July 2021, but accumulation did almost entirely not exceed the LoD.

Dormant dune fields and ameliorative moisture conditions in the West Gobi Desert in East Asia during the Last Interglacial. Zheng, Junge; Zhang, Deguo; Yang, Xiaoping; Lehmkuhl, Frank; Stauch, Georg. In Palaeogeography, Palaeoclimatology, Palaeoecology, 643, S. 112170. 2024.

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Arid and semiarid regions are environmentally vulnerable to global warming. Thus, studying their environmental history during warm periods (e.g., the Last Interglacial, LIG) is crucial for understanding their future changes too. The West Gobi Desert is a transitional zone influenced by the westerlies and the East Asian monsoon system. Therefore, the variation in atmospheric circulation profoundly affects its water vapor transport and landscape evolution. Due to the scarcity of continuous records, the moisture transport process remains ambiguous, which limits further research on paleolake evolution and aeolian activity. Here, we combine paleoclimate simulations from the Coupled Model Intercomparison Project 6 (CMIP6)-Paleoclimate Modeling Intercomparison Project 4 (PMIP4) and geological records to clarify the water vapor transport pathways and aeolian activity in the West Gobi Desert during the LIG, compared to the reference period (the piControl). Our results show that increased rainfall and meltwater were possible supplies for surface water during the LIG and were associated with enhanced East Asian summer monsoon and higher surface air temperatures. Concomitantly, weakening aeolian activity and dormant dune fields occurred in the West Gobi Desert, resulting from higher surface moisture content and weaker surface wind regimes associated with the weakening westerlies and East Asian winter monsoon. Notably, the limited weakening of aeolian activity that occurred in the LIG winter and spring was caused by weaker surface wind and deteriorating surface moisture conditions, while the significant dormancy of dune fields in the LIG summer and autumn was initiated by the combined effects of ameliorative surface moisture conditions and lower surface wind speed.

Deglaciation of the highest mountains in Scandinavia at the Younger Dryas–Holocene transition: evidence from surface exposure‐age dating of ice‐marginal moraines. Matthews, John A.; Linge, Henriette; Nesje, Atle; Wilson, Peter; Mourne, Richard W.; Winkler, Stefan; Owen, Geraint; Hill, Jennifer L.; Haselberger, Stefan; Olsen, Jesper. In Boreas, 53(2), S. 139–163. Wiley, 2023.

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Glacier thinning, recession and advance, and the associated evolution of a glacial lake between 1966 and 2021 atAusterdalsbreen, westernNorway.. Seier, Gernot; Abermann, Jakob; Andreassen, Liss M.; Carrivick, Jonathan L.; Kielland, Pål H.; Löffler, Karina; Nesje, Atle; Robson, Benjamin A.; Røthe, Torgeir O.; Scheiber, Thomas; Winkler, Stefan; Yde, Jacob C. In Land Degradation & Development, 35(1), S. 394–414. Wiley, 2023.

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The Jostedalsbreen is the largest ice cap in Norway and mainland Europe. Rapid retreat of many of its outlet glaciers since the 2000s has led to the formation of several glacial lakes. Processes causing the formation and expansion of glacial lakes and their interaction with a glacier and terminal moraine have not been widely addressed yet. In this study, we investigate the degradation of the front of the southeast-facing outlet glacier Austerdalsbreen. Based on a variety of remotely sensed data (UAV-based and airborne orthophotos and DEMs, satellite images), we analyze the coincident glacial and proglacial changes of Austerdalsbreen and quantify the evolution of this transition zone during the last decades. In particular, we focus on the short-term evolution of the glacial lake since 2010, we examine the context of a glacier advance in the 1990s, and we report long-term changes by utilizing 1960s imagery. We discuss the evolution and conditions of Austerdalsbreen compared to other outlet glaciers of Jostedalsbreen. Overall, the glacier terminus has experienced a recession in the last decades. The 1990s terminus advance was more restricted than at other nearby outlet glaciers due to glacier surface debris cover, which is a critical factor for the glacier and lake evolution. However, in the most recent period, since 2012, a distinct expansion of a glacial lake is quantifiable. Since the rates of glacier surface lowering also considerably increased since approximately 2017 and the glacier retreated since the beginning of the 2000s with a clear maximum length decrease in 2015, we interpret the recently formed glacial lake as a contributory factor of glacial changes.

In the land of the apu: Cerro Llamocca as a sacred mountain and central place in the pre-Columbian Andes of southern Peru. Mader, Christian; Reindel, Markus; Isla, Johny; Behl, Martin; Meister, Julia; Hölzl, Stefan. In Journal of Archaeological Science: Reports, 49, S. 104045. Elsevier BV, 2023.

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Similar vegetation‐geomorphic disturbance feedbacks shape unstable glacier forelands across mountain regions. Eichel, Jana; Draebing, Daniel; Winkler, Stefan; Meyer, Nele. In Ecosphere, 14(2). Wiley, 2023.

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Glacier forelands are among the most rapidly changing landscapes on Earth. Stable ground is rare as geomorphic processes move sediments across large areas of glacier forelands for decades to centuries following glacier retreat. Yet, most ecological studies sample exclusively on stable terrain to fulfill chronosequence criteria, thus missing potential feedbacks between geomorphic disturbances and vegetation colonization. By influencing vegetation and soil development, such vegetation-geomorphic disturbance feedbacks could be crucial to understand glacier foreland ecosystem development in a changing climate. We surveyed vegetation and environmental properties, including geomorphic disturbance intensities, in 105 plots located on both stable and unstable moraine terrain in two geomorphologically active glacier forelands in New Zealand and Switzerland. Our plot data showed that geomorphic disturbance intensities permanently changed from high/moderate to low/stable when vegetation reached cover values of around 40%. Around this cover value, species with response and effect traits adapted to geomorphic disturbances dominated. This suggests that such species can act as “biogeomorphic” ecosystem engineers that stabilize ground through positive feedback loops. Across floristic regions, biogeomorphic ecosystem engineer traits creating ground stabilization, such as mat growth and association with mycorrhiza, are remarkably similar. Nonmetric multidimensional scaling revealed a linked sequence of decreasing geomorphic disturbance intensities and changing species composition from pioneer to late successional species. We interpret this linked geomorphic disturbance-vegetation succession sequence as “biogeomorphic succession,” a common successional pathway in unstable river and coastal ecosystems across the world. Soil and vegetation development were related to this sequence and only advanced once biogeomorphic ecosystem engineer species covered 40%–45% of a plot, indicating a crucial role of biogeomorphic ecosystem engineer stabilization. Different topoclimatic conditions could explain variance in biogeomorphic succession timescales and ecosystem engineer root traits between the glacier forelands. As glacier foreland ground is widely unstable, we propose to consider glacier forelands as “biogeomorphic ecosystems” in which ecosystem structure and function are shaped by geomorphic disturbances and their feedbacks with adapted plant species, similar to rivers and coasts.

Anthropogenic influence of open pit mining on river floods, an example of the Blessem flood 2021. Lehmkuhl, Frank; Stauch, Georg. In Geomorphology, 421, S. 108522-. 2023.

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Large scale anthropogenic relief changes result in a non-equilibrium landscape and such landscapes are prone to catastrophic erosion events during river floods. An example is the major flood event in western German in July 2021. During this event, the Erft River flooded an open gravel pit near the village of Erftstadt-Blessem, resulting in a massive erosional event, including the catastrophic destruction of parts of the settlement. Three different geomorphological periods occurred during the event: I) rapid backward erosion caused the destruction of the overlaying soils and floodplain sediments. Consequently, the gravel pit was filled with water and sediments. Three different pathways of backward erosion were activated during this period. II) Sedimentation in a temporary lake and the formation of alluvial fans. III) The Erft River moved towards the gravel pit due to the erosional processes followed by a second flood. Understanding of such complex erosional and depositional processes in open pit mining areas might serve as a blueprint for processes and hazards in anthropogenic influenced landscapes.

High-resolution digital surface models ({DSM}s) of the Urft River valley (Urft {R}eservoir) from 2020 and 2021, northern Eifel Mountains, western Germany. Stauch, Georg; Dörwald, Lukas; Esch, Alexander; Walk, Janek. 2023.

[ Abstract ]
[ DOI ]

Affiliated publication: Stauch, G., Dörwald, L., Esch, A., Walk, J., 2023. 115 years of sediment deposition in a reservoir in central Europe: Topographic change detection. Earth Surface Processes and Landforms.

Dune movement under climatic changes on the north-eastern Tibetan Plateau as recorded by long-term satellite observation versus ERA-5 reanalysis. Dörwald, Lukas; Lehmkuhl, Frank; Walk, Janek; Delobel, Lucie; Boemke, Bruno; Baas, Andreas; Zhang, Deguo; Yang, Xiaoping; Stauch, Georg. In Earth Surface Processes and Landforms, 48(13), S. 2613–2629. 2023.

[ Abstract ]
[ DOI ]

The movement of active dunes is tightly linked to climatic conditions (e.g., wind regime, temperature and precipitation) as well as human influence (e.g., grazing, dune fixation and greening). Dune migration rates can be studied to draw conclusions of changing wind conditions over time. The Gonghe Basin (GB), located on the north-eastern Tibetan Plateau (TP), offers a good testing ground for these assumptions. The intramontane basin is highly influenced by two major wind regimes: the mid-latitude Westerlies and the East Asian summer monsoon. To investigate environmental changes, this study combines optical remote sensing techniques with climatic datasets. High-resolution satellite images of the last five decades, such as CORONA KH-4B, are used to map dunes and calculate their respective migration rates. Further, height information was extracted as well. Climatic changes from the ERA-5 reanalysis dataset and normalized difference vegetation index (NDVI) values were processed alongside. Relating the dunes' surface processes to climate model data shows an accordance between slowing migration, expanding vegetation and a decrease in sand drift potential. From 1968 to present time, an average dune migration rate of 7.3 m a−1 was extracted from the satellite images, with an overall reduction of −1.81 m a−1. The resultant drift potential (RDP) values for the GB are calculated to be below 10 m3 s−3 with a spatial decrease, following a direction from the NW to the SE, fitting well with a corresponding decrease in the migration rates. Our results indicate a good agreement between the development of aeolian landforms and the ERA-5 climate reanalysis model data, even in a high-altitude setting with complex topography, which is known to influence such datasets.

Pedogenesis at the coastal arid-hyperarid transition deduced from a Late Quaternary chronosequence at Paposo, Atacama Desert. Walk, Janek; Schulte, Philipp; Bartz, Melanie; Binnie, Ariane; Kehl, Martin; Mörchen, Ramona; Sun, Xiaolei; Stauch, Georg; Tittmann, Christopher; Bol, Roland; Brückner, Helmut; Lehmkuhl, Frank. In CATENA, 228, S. 107171. Elsevier BV, 2023.

[ Abstract ]
[ DOI ]

Under hyperarid climate conditions, pedogenesis is driven by the atmospheric deposition and subsequent accumulation of easily to moderately soluble salts forming extreme types of Aridisols. In contrast, the processes and timescales of soil formation in coastal desert environments are as yet not well understood. Therefore, a soil chronosequence at the arid-hyperarid transition in the south-central coastal Atacama Desert is investigated. We measured physicochemical soil parameters of shallow soil profiles on four generations of a multi-stage alluvial fan system, assisted by micromorphological analysis, allowing to deduce the soil-forming processes. We further established a geochronological framework by applying 10Be cosmogenic nuclide exposure dating on the abandoned surface generations, which allowed to infer the timescales for soil formation. The results indicate initial yet clearly identifiable pedogenesis occurring since MIS 5e–c. Along the Late Quaternary chronosequence, physicochemical soil properties show decreasing trends with growing age for the median grain size, salinity, long-term pH development, and CaCO3 contents. Contrarily, organic carbon, the ratio of organic to total phosphorus, the redness, and the contents of total and poorly crystalline pedogenic iron oxides tend to increase with age. This provides evidence for soil formation under an arid to hyperarid coastal climate characterized by (i) redistribution of salts by leaching causing topsoil desalinization; (ii) decalcification coupled with (iii) dealkalinization in totally decalcified horizons; (iv) accumulation of soil organic matter; (v) initial rubification through formation of pedogenic iron oxides (i.e. hematite); and (vi) initial loamification that, in turn, might have impeding effects on the translocation of soil constituents on timescales larger than 105 a. Furthermore, in situ pedogenesis might be superimposed considerably by aeolian dust influx. At Atacama’s south-central coast, the state of pedogenic alteration scales with the cumulative precipitation received throughout the entire Late Quaternary, yet evolved strongest between MIS 5 and the MIS 4/3-transition.

Dune movement under climatic changes on the north‐eastern Tibetan Plateau as recorded by long‐term satellite observation versus ERA‐5 reanalysis. Dörwald, Lukas; Lehmkuhl, Frank; Walk, Janek; Delobel, Lucie; Boemke, Bruno; Baas, Andreas; Zhang, Deguo; Yang, Xiaoping; Stauch, Georg. In Earth Surface Processes and Landforms, 48(13), S. 2613–2629. Wiley, 2023.

[ Abstract ]
[ DOI ]

The movement of active dunes is tightly linked to climatic conditions (e.g., wind regime, temperature and precipitation) as well as human influence (e.g., grazing, dune fixation and greening). Dune migration rates can be studied to draw conclusions of changing wind conditions over time. The Gonghe Basin (GB), located on the north-eastern Tibetan Plateau (TP), offers a good testing ground for these assumptions. The intramontane basin is highly influenced by two major wind regimes: the mid-latitude Westerlies and the East Asian summer monsoon. To investigate environmental changes, this study combines optical remote sensing techniques with climatic datasets. High-resolution satellite images of the last five decades, such as CORONA KH-4B, are used to map dunes and calculate their respective migration rates. Further, height information was extracted as well. Climatic changes from the ERA-5 reanalysis dataset and normalized difference vegetation index (NDVI) values were processed alongside. Relating the dunes' surface processes to climate model data shows an accordance between slowing migration, expanding vegetation and a decrease in sand drift potential. From 1968 to present time, an average dune migration rate of 7.3 m a−1 was extracted from the satellite images, with an overall reduction of −1.81 m a−1. The resultant drift potential (RDP) values for the GB are calculated to be below 10 m3 s−3 with a spatial decrease, following a direction from the NW to the SE, fitting well with a corresponding decrease in the migration rates. Our results indicate a good agreement between the development of aeolian landforms and the ERA-5 climate reanalysis model data, even in a high-altitude setting with complex topography, which is known to influence such datasets.

Pedogenesis at the coastal arid-hyperarid transition deduced from a Late Quaternary chronosequence at Paposo, Atacama Desert. Walk, Janek; Schulte, Philipp; Bartz, Melanie; Binnie, Ariane; Kehl, Martin; Mörchen, Ramona; Sun, Xiaolei; Stauch, Georg; Tittmann, Christopher; Bol, Roland; Brückner, Helmut; Lehmkuhl, Frank. In CATENA, 228, S. 107171-. 2023.

[ Abstract ]
[ DOI ]

Under hyperarid climate conditions, pedogenesis is driven by the atmospheric deposition and subsequent accumulation of easily to moderately soluble salts forming extreme types of Aridisols. In contrast, the processes and timescales of soil formation in coastal desert environments are as yet not well understood. Therefore, a soil chronosequence at the arid-hyperarid transition in the south-central coastal Atacama Desert is investigated. We measured physicochemical soil parameters of shallow soil profiles on four generations of a multi-stage alluvial fan system, assisted by micromorphological analysis, allowing to deduce the soil-forming processes. We further established a geochronological framework by applying 10Be cosmogenic nuclide exposure dating on the abandoned surface generations, which allowed to infer the timescales for soil formation. The results indicate initial yet clearly identifiable pedogenesis occurring since MIS 5e–c. Along the Late Quaternary chronosequence, physicochemical soil properties show decreasing trends with growing age for the median grain size, salinity, long-term pH development, and CaCO3 contents. Contrarily, organic carbon, the ratio of organic to total phosphorus, the redness, and the contents of total and poorly crystalline pedogenic iron oxides tend to increase with age. This provides evidence for soil formation under an arid to hyperarid coastal climate characterized by (i) redistribution of salts by leaching causing topsoil desalinization; (ii) decalcification coupled with (iii) dealkalinization in totally decalcified horizons; (iv) accumulation of soil organic matter; (v) initial rubification through formation of pedogenic iron oxides (i.e. hematite); and (vi) initial loamification that, in turn, might have impeding effects on the translocation of soil constituents on timescales larger than 105 a. Furthermore, in situ pedogenesis might be superimposed considerably by aeolian dust influx. At Atacama’s south-central coast, the state of pedogenic alteration scales with the cumulative precipitation received throughout the entire Late Quaternary, yet evolved strongest between MIS5 and the MIS4/3-transition.

High-resolution digital elevation model ({DEM}) of the Urft River valley (Urft {R}eservoir) from 1897, northern Eifel Mountains, western Germany. Stauch, Georg; Dörwald, Lukas; Esch, Alexander; Walk, Janek. 2023.

[ Abstract ]
[ DOI ]

Affiliated publication: Stauch, G., Dörwald, L., Esch, A., Walk, J., 2023. 115 years of sediment deposition in a reservoir in central Europe: Topographic change detection. Earth Surface Processes and Landforms.

Schmidt-hammer exposure-age dating: a review of principles and practice. Matthews, John A.; Winkler, Stefan. In Earth-Science Reviews, 230, S. 104038. Elsevier BV, 2022.

[ Abstract ]
[ DOI ]

Schmidt-hammer exposure-age dating (SHD) is a numerical, calibrated-age dating technique based on the degree of weathering of rock surfaces. The Schmidt hammer measures the hardness or strength of a rock surface by means of R-values (rebound values), which are produced as the hammer impacts the surface. Age calibration is carried out with reference to at least two surfaces of known age (control surfaces). Mean R-values then yield numerical estimates of the time elapsed since exposure of rock surfaces to subaerial weathering. Under favourable circumstances with a sufficiently large number of impacts, SHD has an age resolution of 300–500 years for rock surfaces exposed during the Holocene and Late Pleistocene, and a current age range of ~25 ka. Accurate independent dating of control surfaces and careful selection of sites to reduce the effects of lithological variability are essential. R-value distributions are an important aid in the interpretation of SHD ages from active and relict, synchronous and diachronous, single and multiple-event surfaces. Important research applications have been made within the fields of Quaternary geochronology, palaeoenvironmental reconstruction, geomorphology and subaerial processes, and landscape dynamics. SHD has been found particularly useful in relation to boulder deposits and bedrock surfaces in glacial and periglacial environments. There is much untapped potential in coastal, temperate and tropical landscapes wherever rock surfaces are exposed to undisturbed rock weathering. The advantages and limitations of SHD compare favourably with the complementary exposure-age technique of terrestrial cosmogenic nuclide dating (TCND). The capability to provide a large number of exposure ages at low cost, and non-destructively in sensitive natural and artefactual settings, are special strengths of SHD.

Age, origin and palaeoclimatic implications of peri- and paraglacial boulder-dominated landforms in Rondane, South Norway. Marr, Philipp; Winkler, Stefan; Dahl, Svein Olaf; Löffler, Jörg. In Geomorphology, 408, S. 108251. Elsevier BV, 2022.

[ Abstract ]
[ DOI ]

Boulder-dominated landforms of periglacial, paraglacial and related origin constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform development initiation and its subsequent stabilization can be linked to past climatic conditions offering the potential to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, rock-slope failure, paraglacial alluvial fan) in Rondane, eastern South Norway for the first time. On the basis of old and young control points a regional SHD calibration curve was established and successively utilized for the calculation of surface exposure ages for individual landforms. The chronological investigation of development and stabilization of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its impact on overall landform evolution. Our obtained SHD age estimates ranged from 11.44 ± 1.22 ka (ST-D2) to 4.09 ± 1.51 ka (AF1) showing their inactive and relict character. Most surface exposure ages for sorted stripes clustered between 9.88 ± 1.35 ka and 9.25 ± 1.21 ka, hence indicating stabilization during the late stage of the Erdalen Event or shortly thereafter. It is inferred that the blockfield formed prior to the Last Glacial Maximum, was protected by cold-based ice throughout glaciation and shortly reactivated during the Erdalen Event only to subsequently becoming inactive. The surface exposure age of a rock-slope failure (7.58 ± 0.73 ka) falls into the early phase of the Holocene Thermal Maximum (HTM, ~8.0–5.0 ka). This indicates permafrost degradation and/or increasing hydrological pressure negatively influencing slope stability. The paraglacial alluvial fan with its four subsites yielded ages between 8.73 ± 1.63 ka and 4.09 ± 1.51 ka. The old exposure ages point to fan aggradation following regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Our results underline the importance of meltwater for the activation of periglacial landforms in a continental climate and indicate that the Erdalen Event and immediately following onset of the HTM had major impact on landscape evolution in Rondane. Our obtained surface exposure ages from boulder-dominated landforms in Rondane give important insights into the local palaeoclimatic variability during the Holocene.

Late Quaternary landscape evolution and paleoenvironmental implications from multiple geomorphic dryland systems, Orog Nuur Basin, Mongolia. Nottebaum, Veit; Stauch, Georg; van der Wal, Jorien L. N.; Zander, Anja; Schlütz, Frank; Shumilovskikh, Lyudmila; Reicherter, Klaus; Batkhishig, Ochirbat; Lehmkuhl, Frank. In Earth Surface Processes and Landforms, 47(1), S. 275–297. 2022.

[ Abstract ]
[ DOI ]

This study investigates the late Quaternary development of the sedimentary system of Orog Nuur Basin in southern Mongolia. Geomorphological archives (lacustrine sediments and beach ridges, alluvial fans, aeolian deposits, peat) recorded palaeoenvironmental change from marine isotope stage (MIS) 7 to the late Holocene. Synthesizing the variety of archives allows a better understanding of geomorphological interactions in arid regions and palaeoenvironmental implications for the area. By performing palaeoshoreline mapping and dating, we identified eight palaeolake levels resulting in a refined lake level history of Orog Nuur. The highest reliably dated shoreline is about 56 m higher than today's lake level and provides evidence for a late MIS 5 lake level between 100 and 75 thousand years (ka). Reconstructions yield a minimum volume estimate of 24.5 km3, delineating a lake that is 153 times larger than that of today (0.16 km3). Massive lake extensions occurred also during MIS 3 and the Holocene. The geomorphological investigation reveals late MIS 5 and MIS 3 lake expansions were of similar magnitude. The palaeoenvironmental reconstruction from early Holocene archives indicates that lake expansion was caused by an increase in precipitation and meltwater inflow from the surrounding mountain systems. Afterwards, lake levels declined with some intermittent highstands during the mid-Holocene (7–5 ka), indicating a general trend towards a lower water inflow throughout the Holocene. Palynological reconstructions of the alpine vegetation development reveal that mid-Holocene highstands (c. 6.5 ka and 5.5 ka) were fed by higher precipitation in the nearby Gurvan Bogd range. Mountain silts, basin silty sands, and Holocene dune deposits provide further evidence for paleoenvironmental change. As controlling factors of the sedimentary system, we identified changes in effective moisture, higher precipitation values and the contribution of meltwater. Orog Nuur Basin archives are valuable for landscape and palaeoenvironmental reconstructions and for comparisons in supraregional reconstruction approaches.

Weathering under coastal hyperaridity – Late Quaternary development of spectral, textural, and gravelometric alluvial fan surface characteristics. Walk, Janek; Bartz, Melanie; Stauch, Georg; Binnie, Ariane; Brückner, Helmut; Lehmkuhl, Frank. In Quaternary Science Reviews, 277, S. 107339-. 2022.

[ Abstract ]
[ DOI ]

Hyperarid coasts develop under relatively high air humidity and abundant sea salt aerosols, resulting in physical and chemical weathering processes that distinctly differ from those present in inland deserts. However, neither the geomorphic effects of the weathering processes nor the timescales on which they alter depositional surfaces are sufficiently understood. In this study we therefore integrate spectral, textural, and gravelometric analyses based on high to very high resolution satellite and aerial remote sensing to assess the degree of post-depositional alteration of a multi-stage alluvial fan at the coast of the Atacama Desert. To further deduce the present-day as well as past intensities of responsible weathering processes we establish a morphochronology of the fan's evolution using cosmogenic 10Be exposure dating. Spectral, textural, and gravelometric parameters relatively date a succession of fan generations, assuming the weathering of fan surface sediments prior to deposition can be largely excluded. Under coastal hyperaridity, effects on the spectral surface signatures are primarily explained by the development of weathering rinds and related formation of secondary iron oxides. Spectral iron oxide ratios show little to no change during the Holocene but strongly increase during the Late Glacial, while over longer timescales an asymptotic increase is suggested. Clast breakdown can largely be attributed to salt weathering causing sublinear to roughly linear decreases in mean size, coarseness, and size variation of coarse clasts. Governed by clast breakdown as well as lateral remobilization of clasts, nano-scale surface roughness exhibits a non-monotonic, peak-shaped relationship with age, whereas the micro-relief experiences continuous smoothing due to denudation. Findings are summarized in a conceptual model showing that in hyperarid coastal environments fan surface weathering results over timescales of 104 to 105 a in a fully developed desert pavement. Two hypothetical scenarios are introduced which differ based on whether desert pavements remain stable over timescales exceeding the Late Pleistocene or not. Late Quaternary weathering intensity along the coast of the Atacama Desert is found to be related to sea surface temperature variability and sea level jointly driving the oceanic moisture supply.

Beispiele für morphodynamische Prozesse und Verlagerungen in Folge des Hochflutereignisses 2021 im Ahrtal. Lehmkuhl, Frank; Keßels, Johannes; Schulte, Philipp; Stauch, Georg; Dörwald, Lukas; Wolf, Stefanie; Brüll, Catrina; Schüttrumpf, Holger. In Wasser und Abfall, 24(11), S. 40–47. 2022.

[ DOI ]

Weathering under coastal hyperaridity – Late Quaternary development of spectral, textural, and gravelometric alluvial fan surface characteristics. Walk, Janek; Bartz, Melanie; Stauch, Georg; Binnie, Ariane; Brückner, Helmut; Lehmkuhl, Frank. In Quaternary Science Reviews, 277, S. 107339. Elsevier BV, 2022.

[ Abstract ]
[ DOI ]

Hyperarid coasts develop under relatively high air humidity and abundant sea salt aerosols, resulting in physical and chemical weathering processes that distinctly differ from those present in inland deserts. However, neither the geomorphic effects of the weathering processes nor the timescales on which they alter depositional surfaces are sufficiently understood. In this study we therefore integrate spectral, textural, and gravelometric analyses based on high to very high resolution satellite and aerial remote sensing to assess the degree of post-depositional alteration of a multi-stage alluvial fan at the coast of the Atacama Desert. To further deduce the present-day as well as past intensities of responsible weathering processes we establish a morphochronology of the fan's evolution using cosmogenic 10Be exposure dating. Spectral, textural, and gravelometric parameters relatively date a succession of fan generations, assuming the weathering of fan surface sediments prior to deposition can be largely excluded. Under coastal hyperaridity, effects on the spectral surface signatures are primarily explained by the development of weathering rinds and related formation of secondary iron oxides. Spectral iron oxide ratios show little to no change during the Holocene but strongly increase during the Late Glacial, while over longer timescales an asymptotic increase is suggested. Clast breakdown can largely be attributed to salt weathering causing sublinear to roughly linear decreases in mean size, coarseness, and size variation of coarse clasts. Governed by clast breakdown as well as lateral remobilization of clasts, nano-scale surface roughness exhibits a non-monotonic, peak-shaped relationship with age, whereas the micro-relief experiences continuous smoothing due to denudation. Findings are summarized in a conceptual model showing that in hyperarid coastal environments fan surface weathering results over timescales of 104 to 105 a in a fully developed desert pavement. Two hypothetical scenarios are introduced which differ based on whether desert pavements remain stable over timescales exceeding the Late Pleistocene or not. Late Quaternary weathering intensity along the coast of the Atacama Desert is found to be related to sea surface temperature variability and sea level jointly driving the oceanic moisture supply.

Smartphone-supported mapping of landforms – A new tool in teaching geomorphology. Stauch, Georg. In Erdkunde, 76(3), S. 227–234. 2022.

[ Abstract ]
[ DOI ]

Understanding 3D properties of objects is an integral part of geomorphological teaching. This can best be achieved during field trips. However, there are numerous reasons why teaching outdoor might not be possible, either for a group of students or just individuals. 3D models of landforms, either static or interactive, are a great method to improve students learning success, e.g. in a blended learning environment. Preparation of 3D models of individual geomorphological landforms has been so far time-consuming. But since 2020, LiDAR sensors have been integrated into some new smartphones. These systems offer great potential for geomorphological teaching, as they enable simple and cost-effective recording of geomorphological landforms and objects in three dimensions. The smartphone LiDAR systems are suitable for the documentation and 3D reconstruction of objects in the range of several decimetres to metres. By means of three examples, the possible applications of smartphone-based LiDAR systems in the field of geomorphological teaching will be demonstrated. All in all, these smartphone LiDAR systems offer great potential, as they support the understanding of the three-dimensional structure of geomorphological landforms and objects in teaching in schools and universities and thus increase the success of teaching among pupils and students. Furthermore, 3D models make geomorphology more inclusive, e.g. for people not able to conduct field work. At the same time, in research, they offer new opportunities for scientific observation projects, e.g. through the continuous monitoring of geomorphological changes in the context of Citizen Science projects.

New evidence for active talus-foot rock glaciers at Øyberget, southern Norway, and their development during the Holocene. Nesje, Atle; Matthews, John A; Linge, Henriette; Bredal, Marie; Wilson, Peter; Winkler, Stefan. In The Holocene, 31(11–12), S. 1786–1796. SAGE Publications, 2021.

[ Abstract ]
[ DOI ]

Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530 m above sea level, with an estimated mean annual air temperature of ~1.6°C, currently exhibit deformation attributed to viscous creep. Five years of InSAR measurements for six lobes demonstrate average surface velocities of 1.2–22.0 mm/year with maximum rates of 17.5–55.6 mm/year. New Schmidt-hammer exposure-age dating (SHD) of two proximal lobes reveals mid-Holocene ages (7.6 ± 1.3 ka and 6.0 ± 1.2 ka), which contrast with the early-Holocene SHD and 10Be ages obtained previously from distal lobes, and late-Holocene SHD ages presented here from two adjacent talus slopes (2.3 ± 1.0 ka and 2.4 ± 1.0 ka). Although passive transport of boulders on the surfaces of these small, slow-moving rock glaciers affected by compressive flow means that the exposure ages are close to minimum estimates of the time elapsed since lobe inception, disturbance of boulders on rock glaciers is a source of potentially serious underestimates of rock-glacier age. Rock-glacier development at Øyberget began shortly after local deglaciation around 10 ka before present and continued throughout the Holocene in response to microclimatic undercooling within the coarse blocky surface layer of the talus and rock-glacier lobes. We suggest this enhanced cooling lowers mean annual surface-layer temperature by at least ~3.6°C, which is needed at such a low altitude to sustain sporadic permafrost and avoid fast thawing as atmospheric temperatures rise. Our results point to circumstances where inferences about rock glaciers as indicators of regional climate should be interpreted with caution, and where they may be less useful in palaeoclimatic reconstruction than previously thought.

Late Pleistocene–Holocene pedogenesis and palaeoclimate in western Asia from palaeosols of the Central Iranian Plateau. Rashidi, Zakieh; Karimi, Alireza; Murray, Andrew; Khormali, Farhad; Farpoor, Mohammad Hady; Sohbati, Reza. In Boreas, 51(1), S. 201–218. Wiley, 2021.

[ DOI ]

Why analysing microplastics in floodplains matters: application in a sedimentary context. Lechthaler, Simone; Esser, Verena; Schüttrumpf, Holger; Stauch, Georg. In Environmental Science: Processes & Impacts, 23(1), S. 117–131. 2021.

[ Abstract ]
[ DOI ]

Microplastics in the environment are a relatively new form of anthropogenic contamination. Right now, the research focus is on the detection of microplastic accumulation in different environmental compartments and understanding the processes that have led to its transport. Detailed information on microplastics in floodplain areas and their distribution in depth are still missing to better understand accumulation points. Therefore, this study presents on the one hand microplastic detection in fluvial sediments from nine sampling sites along a river course. Polymers were determined with infrared spectroscopy and additional sedimentary analysis of the grain size and heavy metal concentration was performed. In total, there was less microplastic in the upper than in the lower river course and slip-off slopes were identified as accumulation hotspots also in deeper sediment layers. Mostly, microplastic particles were detected in fine sediment and heavy metal concentrations along the river were similar to those of microplastics. On the other hand, besides the spatial distribution of microplastics and accumulation in floodplain areas, microplastic analysis offered information in a sedimentary context. Sedimentation rates (0.29–4.00 cm a−1) and patterns between temporal deposition and microplastic polymers were identified. The basis for the development of a dating method by detection of MPs in sediments was thus established. Microplastics as a contaminant provide, in addition to the identification of deposition areas, further data in a temporal and sedimentary perspective.

Schmidt-hammer exposure-age dating (SHD) of sorted stripes on Juvflye, Jotunheimen (central South Norway): Morphodynamic and palaeoclimatic implications. Winkler, Stefan; Matthews, John A.; Haselberger, Stefan; Hill, Jennifer L.; Mourne, Richard W.; Owen, Geraint; Wilson, Peter. In Geomorphology, 353, S. 107014. Elsevier BV, 2020.

[ DOI ]

Arsenic distribution and pathway scenarios for sediments and water in a peri-urban Mongolian small-scale coal mining area (Nalaikh District, Ulaanbaatar). Nottebaum, Veit; Walk, Janek; Knippertz, Martin; Karthe, Daniel; Batbayar, Gunsmaa; Pötter, Stephan; Lehmkuhl, Frank. In Environmental Science and Pollution Research, 27(6), S. 5845–5863. 2019.

[ Abstract ]
[ DOI ]

The distribution of arsenic (As) in environmental compartments is investigated in the Nalaikh Depression of N-Mongolia. In Nalaikh, lignite coal is mined by artisanal small-scale mining (ASM) approaches. Because As is often associated with sulfuric minerals in coal, it was hypothesized that enrichment of As is related to coal ASM. A second hypothesis considered coal combustion in power plants, and stoves are a key source of As in the local environment. Three mobilization and distribution scenarios were developed for potential As pathways in this semiarid environment. About 43 soil and 14 water sites were analyzed for As concentrations and meaningful parameters in soil and water. About 28 topsoil samples were analyzed in surface-subsurface pairs in order to identify potential eolian surface enrichment. Additionally, fluvial-alluvial sediments and geogenic and anthropogenic deposits were sampled. Water was sampled as surface water, groundwater, precipitation, and industrial water. Results show that As does not pose a ubiquitous risk in the Nalaikh Depression. However, locally and specifically in water, As concentrations may exceed the WHO guideline value for drinking water by up to a factor of 10. A carefully selected sampling strategy allows the evaluation of the distribution scenarios, which reveals a combination of (a) geogenic As in groundwater and distribution via surface water with (b) anthropogenic As redistribution via eolian pathways. An immediate linkage between As redistribution and coal mining is not evident. However, As distribution in fly ash from coal combustion in the local power plant and yurt settlements is the most likely As pathway. Hence, the results indicate the potential influence of diffuse, low-altitude sources on As emission to the environment. As such, this study provides a good example for As distribution under semiarid climate conditions influenced by geogenic and anthropogenic factors.

Morphotectonics of the northern Bogd fault and implications for Middle Pleistocene to modern uplift rates in southern Mongolia. van der Wal, Jorien L.N; Nottebaum, V.C; Gailleton, B.; Stauch, G.; Weismüller, C.; Batkhishig, O.; Lehmkuhl, F.; Reicherter, K. In Geomorphology, 367, S. 107330-. 2020.

[ Abstract ]
[ DOI ]

Assessing the activity of strike-slip faults is often facilitated by cumulative offsets of morphological features. The December 4th 1957 Mongolia earthquake, generally referred to as the “Gobi Altai” or “Bogd” earthquake, had MW 8.1 and created long and complex surface ruptures of c. 350 km length along the Bogd fault that cuts across the foothills of the Gurvan Bogd mountains. Several left-laterally and vertically displaced Quaternary alluvial fans and morphogenic markers show cumulative offsets, allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution. We propose to expand the active tectonic record along this fault up to a Middle Pleistocene time scale that spans regional climatic fluctuations, i.e. repeated glacial-interglacial cycles, and hence varying erosional and depositional rates. Five main drainage areas crosscutting the North Ikh Bogd segment of the Bogd fault were analysed and compared in terms of hypsometry, drainage steepness and alluvial fan slope inclination. Along the mountain front, deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition-incision cycles. Previously published ages, as well as the spatial distribution of these fan levels, suggest that their incision and abandonment is induced by regionally dominant climate fluctuations. However, the increase of fan slope angles over time and the increased intensity of sub-surface folding observed in ground-penetrating radar profiles, suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology. Estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that Middle Pleistocene to modern vertical slip rates along the North Ikh Bogd segment of the Bogd fault are in the order of 0.9–1 mm/yr. However, much slower vertical slip rates along individual fault segments, ranging between 0.06 ± 0.01 mm/yr and 0.28 ± 0.07 mm/yr, indicate that uplift of the Ikh Bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans. Our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation.

The Way of Macroplastic through the Environment. Lechthaler, Simone; Waldschläger, Kryss; Stauch, Georg; Schüttrumpf, Holger. In Environments, 7(10), S. 73-. 2020.

[ Abstract ]
[ DOI ]

With the focus on microplastic in current research, macroplastic is often not further considered. Thus, this review paper is the first to analyse the entry paths, accumulation zones, and sinks of macroplastic in the aquatic, terrestrial, and atmospheric environment by presenting transport paths and concentrations in the environment as well as related risks. This is done by applying the Source–Pathway–Receptor model on macroplastic in the environment. Based on this model, the life cycle of macroplastic is structurally described, and knowledge gaps are identified. Hence, current research aspects on macroplastic as well as a sound delimitation between macro- and microplastic that can be applied to future research are indicated. The results can be used as basic information for further research and show a qualitative assessment of the impact of macroplastic that ends up in the environment and accumulates there. Furthermore, the applied model allows for the first time a quantitative and structured approach to macroplastic in the environment.

Gradients in climate, geology, and topography affecting coastal alluvial fan morphodynamics in hyperarid regions – The Atacama perspective. Walk, Janek; Stauch, Georg; Reyers, Mark; Vásquez, Paulina; Sepúlveda, Fernando A.; Bartz, Melanie; Hoffmeister, Dirk; Brückner, Helmut; Lehmkuhl, Frank. In Global and Planetary Change, 185, S. 102994-. 2020.

[ Abstract ]
[ DOI ]

Along the coast of the hyperarid Atacama Desert, late Quaternary alluvial fans emerge from the Coastal Cordillera to the Pacific Ocean between 20.5°S and 25.5°S. Coastal alluvial fans (CAF) show, in comparison to the interior fans of the Atacama Desert, pronounced recent activity. However, the complex interplay between climate, lithology, and tectonics affecting the CAF morphodynamics in such hyperarid coastal settings needs to be better understood. We therefore aim at assessing the major factors driving CAF activity and evaluate their effects along gradients. We conducted an extensive study relating climatic, lithologic, and tectonic characteristics to fan and catchment geomorphology of 123 CAF. Geomorphometric analyses are based on the 12.5 m TanDEM-X WorldDEM™, catchment lithology and faults are extracted from 13 regional geological maps, and the frequency of heavy rainfall events capable of activating CAF is derived from a Weather Research and Forecasting (WRF) regional climate model. Our results point to a primary climatic control on CAF morphodynamics shown in functional relationships with catchment hydromorphometric characteristics reflecting a high susceptibility to debris flows – the main CAF-constructing process. Catchment properties along the latitudinal gradient reflect the source of significant precipitation events: frontal systems and cut-off lows which mainly originate in the extratropics and become increasingly rare towards the north. The frequency of precipitation extremes can only be correlated to the hydromorphometry and geomorphic maturity of catchments that feature a high degree of sediment transport potential and generally do not cut back far into the Coastal Cordillera. Related to the strongly reduced influence of the Pacific precipitation source towards the east, this additional climatic transition is governed by the orographic effect of the steep W-E gradient in topography. In contrast, source-area lithology is of negligible relevance for CAF catchment morphometry and fan activity. An important indirect influence of tectonics, however, can be seen in the long-term (neo)tectonic activity within the Coastal Cordillera, which in turn shapes catchments and controls the topography.

Late Pleistocene alluvial fan evolution along the coastal Atacama Desert (N Chile). Bartz, Melanie; Walk, Janek; Binnie, Steven A.; Brill, Dominik; Stauch, Georg; Lehmkuhl, Frank; Hoffmeister, Dirk; Brückner, Helmut. In Global and Planetary Change, 190, S. 103091. Elsevier BV, 2020.

[ Abstract ]
[ DOI ]

Due to their sensitivity to both tectonic activity and climatic variations, coastal alluvial fans (CAF) along the western flank of the Coastal Cordillera in the Atacama Desert (northern Chile) are important geo-archives for unravelling Quaternary environmental change. Our study focuses on terrestrial and marine deposits of five CAF complexes between 20° and 25°S along the coastal zone of the Atacama to identify phases of alluvial fan activity during the Late Quaternary. Based on a combination of luminescence dating and 10Be cosmogenic nuclide exposure dating as well as existing chronological data in the area, insights into climatic variations along the hyper-arid coast are presented for the Late Pleistocene derived from CAF morphodynamics. Activity of alluvial fans could be documented during time spans 95–80 ka, 60–45 ka, 35–20 ka, as well as the Holocene. Numerical dating of marine terrace deposits gives insights into the tectonic uplift of the Coastal Plain in northern Chile during the Late Quaternary period, for which estimated uplift rates between ~0.06 and ~0.57 m/ka were derived. While tectonic activity induces base-level changes, long-term tectonic activity rather indirectly controls alluvial fan activity. We suggest that alluvial fan activity is mainly controlled by atmospheric changes from the Pacific Ocean. Based on our observations, CAF in the hyper-arid Atacama Desert serve as suitable geo-archives for reconstructing climate changes during the Quaternary. In particular, the usefulness of alluvial fan systems in a water-limited environment is important for understanding the palaeoenvironmental evolution in a coastal desert.

Late Pleistocene alluvial fan evolution along the coastal Atacama Desert (N Chile). Bartz, Melanie; Walk, Janek; Binnie, Steven A.; Brill, Dominik; Stauch, Georg; Lehmkuhl, Frank; Hoffmeister, Dirk; Brückner, Helmut. In Global and Planetary Change, 190, S. 103091-. 2020.

[ Abstract ]
[ DOI ]

Due to their sensitivity to both tectonic activity and climatic variations, coastal alluvial fans (CAF) along the western flank of the Coastal Cordillera in the Atacama Desert (northern Chile) are important geo-archives for unravelling Quaternary environmental change. Our study focuses on terrestrial and marine deposits of five CAF complexes between 20° and 25°S along the coastal zone of the Atacama to identify phases of alluvial fan activity during the Late Quaternary. Based on a combination of luminescence dating and 10Be cosmogenic nuclide exposure dating as well as existing chronological data in the area, insights into climatic variations along the hyper-arid coast are presented for the Late Pleistocene derived from CAF morphodynamics. Activity of alluvial fans could be documented during time spans 95–80 ka, 60–45 ka, 35–20 ka, as well as the Holocene. Numerical dating of marine terrace deposits gives insights into the tectonic uplift of the Coastal Plain in northern Chile during the Late Quaternary period, for which estimated uplift rates between ~0.06 and ~0.57 m/ka were derived. While tectonic activity induces base-level changes, long-term tectonic activity rather indirectly controls alluvial fan activity. We suggest that alluvial fan activity is mainly controlled by atmospheric changes from the Pacific Ocean. Based on our observations, CAF in the hyper-arid Atacama Desert serve as suitable geo-archives for reconstructing climate changes during the Quaternary. In particular, the usefulness of alluvial fan systems in a water-limited environment is important for understanding the palaeoenvironmental evolution in a coastal desert.

Regional study of microplastics in surface waters and deep sea sediments south of the Algarve Coast. Lechthaler, Simone; Schwarzbauer, Jan; Reicherter, Klaus; Stauch, Georg; Schüttrumpf, Holger. In Regional Studies in Marine Science, 40, S. 101488-. 2020.

[ Abstract ]
[ DOI ]

Various studies show a contamination of the marine environment with microplastics due to the material persistence and a resulting accumulation. Right now, the environmental impact of microplastics is not fully determined and in order to obtain further information on contaminated areas, water surface samples and (deep sea) sediment from the Atlantic Ocean south of Algarve Coast (Portugal) were taken and analysed. Microfibres, 3 black fibres, were visually detected in 2 of the 20 sediment samples without verifying their polymeric identity. Assuming that they are microplastics, concentration from 0.00–0.29 particles/g dry sediment result. In the eleven water samples, 81.8% contained microplastics including polymeric identification (0.00–14.09 particles/m3) with an average contamination of 1.36 ± 4.03 particles/m3. A significant positive correlation between the microplastic concentration in the water and the average water depth during sampling was identified. This regional study is one of a few that analysed also deep sea sediment and provides results about microplastics as anthropogenic contaminants south of the Algarve coast.

Testing the potential of K-feldspar pIR-IRSL and quartz ESR for dating coastal alluvial fan complexes in arid environments. Bartz, Melanie; Duval, Mathieu; Brill, Dominik; Zander, Anja; King, Georgina E.; Rhein, Alexander; Walk, Janek; Stauch, Georg; Lehmkuhl, Frank; Brückner, Helmut. In Electron spin resonance (ESR) dating in Quaternary studies: evolution, recent advances and applications, 556, S. 124–143. 2020.

[ Abstract ]
[ DOI ]

Coastal alluvial fans (CAF) are important geo-archives due to their sensitivity to both tectonic activity and climatic changes. Thus, they can give key insights for geomorphic and sedimentary processes. In this study we test the potential of K-feldspar post infrared-infrared stimulated luminescence (pIR-IRSL) and quartz electron spin resonance (ESR) methods for dating alluvial fan complexes in arid environments. The existing chronological data from marine terraces that interact with CAF make the Atacama Desert in northern Chile an excellent setting for this research. Samples have been collected from alluvial, marine and aeolian sediments embedded in the CAF complexes, allowing evaluation of the different signal properties and bleaching characteristics of the pIR-IRSL and ESR signals over Late Pleistocene time scales. pIR-IRSL dose distributions of clast-rich alluvial fan samples are characterised by higher scatter and demonstrate heterogeneous bleaching, while matrix-rich alluvial fan deposits show rather homogeneous poor bleaching in the dose dispersion as indicated by a modern analogue sample. In contrast, marine and aeolian deposits are homogeneously well bleached, supported by a modern littoral sample. Following the quartz multiple centre (MC) ESR dating approach (Al and Ti centres), bleaching of the different centres prior to deposition has been achieved. While the Ti–H centre provides mostly lower doses than the Ti–Li centre, in most cases the Al centre provides the highest dose values. This pattern is consistent with their respective bleaching kinetics and suggests that the Ti centre signals most likely provide the closest estimate to the true burial dose for samples with doses >200 Gy. ESR and pIR-IRSL ages are consistent at 2σ for the marine, aeolian and clast-rich debris-flow deposits, which is in agreement with existing chronological data in this area. It appears that the mode of sediment transport on alluvial fans, either as matrix- or clast-rich flows, plays an important role in sediment bleaching. While clast-rich alluvial fan deposits are likely better bleached, we cannot exclude insufficient bleaching during matrix-rich alluvial fan flows; our dating results suggest that both pIR-IRSL and ESR dating overestimate the true burial age. The combination of pIR-IRSL and MC ESR dating can be considered as a promising tool for deciphering alluvial fan formation over (Late) Pleistocene time scales.

Oil Extraction as Separation Method for Microplastic in Sediment Samples. Lechthaler, Simone; Stauch, Georg; Schüttrumpf, Holger. M. Cocca, E. Di Pace, M. E. Errico, G. Gentile, A. Montarsolo, R. Mossotti, M. Avella (Hrsg.), S. 282–286. Springer International Publishing, 2020.

[ Abstract ]

Microplastic (MP), plastic particles smaller than 5 mm [1], is widely distributed in the environment [2] and has not only been detected in the aquatic environment [3] but also in terrestrial areas [4]. To understand the whole life cycle of MP it is important to analyse samples from different areas. With the detection of MP in different environmental compartments, it is possible to define sources, entry and transport paths and temporary and ultimate sinks of MP.

Gradients in climate, geology, and topography affecting coastal alluvial fan morphodynamics in hyperarid regions – The Atacama perspective. Walk, Janek; Stauch, Georg; Reyers, Mark; Vásquez, Paulina; Sepúlveda, Fernando A.; Bartz, Melanie; Hoffmeister, Dirk; Brückner, Helmut; Lehmkuhl, Frank. In Global and Planetary Change, 185, S. 102994. Elsevier BV, 2020.

[ Abstract ]
[ DOI ]

Along the coast of the hyperarid Atacama Desert, late Quaternary alluvial fans emerge from the Coastal Cordillera to the Pacific Ocean between 20.5°S and 25.5°S. Coastal alluvial fans (CAF) show, in comparison to the interior fans of the Atacama Desert, pronounced recent activity. However, the complex interplay between climate, lithology, and tectonics affecting the CAF morphodynamics in such hyperarid coastal settings needs to be better understood. We therefore aim at assessing the major factors driving CAF activity and evaluate their effects along gradients. We conducted an extensive study relating climatic, lithologic, and tectonic characteristics to fan and catchment geomorphology of 123 CAF. Geomorphometric analyses are based on the 12.5 m TanDEM-X WorldDEM™, catchment lithology and faults are extracted from 13 regional geological maps, and the frequency of heavy rainfall events capable of activating CAF is derived from a Weather Research and Forecasting (WRF) regional climate model. Our results point to a primary climatic control on CAF morphodynamics shown in functional relationships with catchment hydromorphometric characteristics reflecting a high susceptibility to debris flows – the main CAF-constructing process. Catchment properties along the latitudinal gradient reflect the source of significant precipitation events: frontal systems and cut-off lows which mainly originate in the extratropics and become increasingly rare towards the north. The frequency of precipitation extremes can only be correlated to the hydromorphometry and geomorphic maturity of catchments that feature a high degree of sediment transport potential and generally do not cut back far into the Coastal Cordillera. Related to the strongly reduced influence of the Pacific precipitation source towards the east, this additional climatic transition is governed by the orographic effect of the steep W-E gradient in topography. In contrast, source-area lithology is of negligible relevance for CAF catchment morphometry and fan activity. An important indirect influence of tectonics, however, can be seen in the long-term (neo)tectonic activity within the Coastal Cordillera, which in turn shapes catchments and controls the topography.

Canola Oil Extraction in Conjunction with a Plastic Free Separation Unit Optimises Microplastics Monitoring in Water and Sediment. Lechthaler, Simone; Hildebrandt, Lars; Stauch, Georg; Schüttrumpf, Holger. In Analytical Methods. 2020.

[ Abstract ]
[ DOI ]

Microplastics are widely distributed in the environment and to define contamination hot spots, environmental samples have to be analysed by means of cost- as well as time-efficient and reliable standardised protocols. Due to the lipophilic characteristics of plastic, oil extraction as a fast and density-independent separation is beneficial for the crucial extraction step. It was extensively validated (480 experiments) in two test setups by using canola oil and a cost-effective, plastic-free separation unit with spiked microplastic (19 different polymer types) in the density range from ρ = 11 - 1,760 kg/m³ and in the size range from 0.02 mm - 4.4 mm. Thus, an innovative, new method combination was developed and profoundly validated for water and sediment samples using only a short settling time of 15 minutes. Some experiments were also carried out with zinc chloride to obtain additional reference data (particles ≤ 359 µm). The total mean recovery rate was 89.3%, 91.7% within the larger microplastic fraction and 85.7% for the small fraction. Compared to zinc chloride (87.6%), recovery rates differed not significantly with oil (87.1%). Furthermore, size limits were set, since the method works best with particles 0.02 mm ≥ d ≤ 3 mm. The proposed method exhibits higher efficiency (84.8% for 20 - 63 µm) for the potentially most harmful microplastic size fraction than the classic setup using brine solution. As a result, oil is a comparably effective separation medium and offers further advantages for separating water and sediment samples due to its density independence, simple and fast application and environmental friendliness. Based on this, a new extraction protocol is presented here that confirms oil separation as a sound and effective separation in microplastic analysis and identifies previously missing information.

The way of microplastic through the environment – Application of the source-pathway-receptor model (review). Waldschläger, Kryss; Lechthaler, Simone; Stauch, Georg; Schüttrumpf, Holger. In Science of The Total Environment, 713, S. 136584-. 2020.

[ Abstract ]
[ DOI ]

Microplastics in the environment is a highly relevant research topic. However, although more and more studies on environmental concentrations of microplastics are published, a profound risk assessment could not be carried out yet. This is mainly attributable to the fact that the current sampling and analysis methods do not provide a representative picture of the environmental pollution, as the fundamental knowledge about transport processes of microplastic is not present, and the ecotoxicological studies therefore cannot consider the relevant exposures of the organisms. To provide a methodological basis for further research and risk assessments, this paper applies the Source-Pathway-Receptor model to the context of microplastics, whereby the current state of knowledge can be compiled in a structured way and important knowledge gaps can be identified.

Alluvial fans along the coastal Atacama Desert - landforms, processes, and evolution. Technical Report (PhD dissertation), . Walk, Janek. PhD dissertation, S. 165. Rheinisch-Westfälische Technische Hochschule Aachen, Aachen, 2020.

[ Abstract ]
[ DOI ]

Alluvial fans represent the dominant sedimentary systems within and along the margins of mountain regions where laterally confined, sediment-rich flows enter open plains or broader valleys. Successive aggradation creates a fan-shaped depositional landform featuring a complex internal architecture. Due to the direct coupling of alluvial fans to the source area, they are principally simple sediment routing systems and ideal archives to study local fluvial morphodynamics but also long-term landscape responses to (palaeo) climatic variability, tectonic activity, and base level changes. In most settings, however, it remained challenging to decipher these allogenic environmental controls. Along the coast of the hyperarid Atacama Desert in northern Chile (20.5°S-25.5°S), alluvial fans radiate from the steep western flank of the Coastal Cordillera, presenting the source area, over the narrow Coastal Plain, the sink. In the distal part, the coastal alluvial fans (CAF) interact with the marine environment, which forms an additional external control. In contrast to the last major alluvial activity in the interior Atacama Desert, dating back to the Miocene to Pliocene, the onset of CAF formation is much younger and CAF show a higher recent activity. However, the timing of their activity beyond the Holocene has barely received any attention yet. A major influence of climate on CAF formation has been proposed for a small part of the coastal Atacama; however, the interplay of climate, lithology, and tectonics in conjunction with strong, marine-driven base-level changes is still insufficiently explored. Hence, the CAF of the Atacama Desert are investigated in this comprehensive study as archives for recent to past sediment transport dynamics under coupled allogenic forcing. For this purpose, the CAF morphology as well as sedimentology, primary processes constructing the alluvial fans, relationships between the CAF systems’ hydromorphometry and the prevailing environmental characteristics (climate, tectonics, and source-area lithology), and the timing of their Quaternary evolution were assessed. While detailed field studies were concentrated on five key sites, overarching large-scale analyses of regional climatic and geologic geodata as well as geomorphometric analyses included 123 CAF systems.Results reveal that alluvial fans along the coastal Atacama Desert are in an overall advanced evolutionary state featuring voluminous aggradation and in approximately half of all cases also significant to deep entrenchment. Detailed geomorphological mapping and morphometric terrain analysis at the CAF complex Guanillos (21.97°S), enabled - besides the introduction of a multi-phase morphostratigraphic model comprising the fan’s prograde evolution and successive incision - to infer debris flows as the main depositional process in this hyperarid coastal setting. The morphological evidence is further supported by the CAF stratigraphy described in detail at five sites. Secondarily, hyperconcentrated flows were found to contribute to a large extent to the CAF aggradation. In contrast, sheetfloods are of negligible relevance, which is in accordance with previous sedimentological observations. Functional relationships between hydromorphometric catchment characteristics, the frequency of extreme precipitation events, fault density, and source-area lithology suggest a primarily climatic control on the CAF morphodynamics. Mostly restricted to catchments draining the western flank of the Coastal Cordillera, a higher frequency of precipitation extremes correlates positively with morphometric parameters indicating an increased susceptibility to debris flows (mean catchment gradient and basin relief ratio) as well as geomorphic catchment maturity. Spatial trends in catchment hydromorphometry and maturity reflect the major climatic source of rainfall events capable of creating effective sediment mobilization: frontal systems and cut-off lows which originate from the extratropical austral Westerlies and become increasingly rare towards the north. Furthermore, an increasing density of Loma vegetation can be observed towards higher latitudes so that possible feedback mechanisms of biota on sediment supply need to be considered for the southern CAF catchments. The relationships between climate and CAF morphodynamics are only seen in the geomorphometry of catchments characterized by a high degree of sediment connectivity and generally do not cut back far into the hinterlands of the Coastal Cordillera. Reflecting the strongly reduced influence of the Pacific precipitation source to the E, this sharp longitudinal climatic transition is governed by the orographic effect of the Coastal Cordillera’s steep topography. In contrast, source-area lithology could be excluded as a major controlling factor for CAF depositional processes along the coastal Atacama Desert. An important indirect influence of tectonics, however, can be seen in the long-term (neo)tectonic activity within the Coastal Cordillera, which in turn shapes catchments and controls the topography. CAF aggradation - those in the Late Pleistocene dated within the context of this study - shows peaks during the marine isotope stage (MIS) 5 (95-80 ka), MIS 3 (60-45 ka), Last Glacial Maximum (LGM) (35-20 ka), and Holocene (⪅7 ka). Those phases all coincide with more humid periods related to (i) warmer sea-surface temperatures (SST) of the SE Pacific provoking a southward shift of the Inter-Tropical Convergence Zone (ITCZ) in MIS 5 and parts of MIS 3, (ii) a weakening of the SE Pacific anticyclone and equatorward shift of the austral Westerlies during the LGM, and (iii) the onset of the modern El Niño-Southern Oscillation (ENSO) in the Middle Holocene characterized by positive SST during El Niño, which in turn favours convection of northward reaching atmospheric humidity and thus torrential rainfall. The coupling of CAF palaeoactivity to wetter phases implies that alluvial fan aggradation in the hyperarid Atacama Desert is primarily controlled by climate and is strongly transport-limited. At the CAF key site Botija (24.57°S), incision of the main channel occurred since the late MIS 3 to early LGM and can be interpreted as either a climate-driven effect due to the northward shift of the Southern Westerlies in MIS 2, the result of sudden base-level fall due to short-term megathrust earthquakes, or simply internal alluvial fan dynamics governed by autogenic controls. Regarding the onset of Pleistocene CAF formation, it cannot be excluded that remnants older than MIS 5 are buried under the younger, dated deposits. Further geochronological data along the coast is thus required to check, whether the widespread geomorphic changes of the CAF are a systematic response to an allogenic environmental control. Nonetheless, the CAF represent crucial archives for the Late Quaternary palaeoclimate of the hyperarid Atacama Desert, which preserve the climatic changes driven by the SE Pacific Ocean to a much higher degree than the interior alluvial fans. Besides the dominant control of climate on CAF evolution, tectonic impulses exert a significant short-term influence by sudden large-magnitude earthquakes changing the CAF base-level independently of eustatic sea-level changes. Against this background, mean Late Quaternary coastal uplift rates between ~0.06 and ~0.57 m/ka were derived from the datings of the elevated marine terraces.

Testing the potential of K-feldspar pIR-IRSL and quartz ESR for dating coastal alluvial fan complexes in arid environments. Bartz, Melanie; Duval, Mathieu; Brill, Dominik; Zander, Anja; King, Georgina E.; Rhein, Alexander; Walk, Janek; Stauch, Georg; Lehmkuhl, Frank; Brückner, Helmut. In Quaternary International, 556, S. 124–143. Elsevier BV, 2020.

[ Abstract ]
[ DOI ]

Coastal alluvial fans (CAF) are important geo-archives due to their sensitivity to both tectonic activity and climatic changes. Thus, they can give key insights for geomorphic and sedimentary processes. In this study we test the potential of K-feldspar post infrared-infrared stimulated luminescence (pIR-IRSL) and quartz electron spin resonance (ESR) methods for dating alluvial fan complexes in arid environments. The existing chronological data from marine terraces that interact with CAF make the Atacama Desert in northern Chile an excellent setting for this research. Samples have been collected from alluvial, marine and aeolian sediments embedded in the CAF complexes, allowing evaluation of the different signal properties and bleaching characteristics of the pIR-IRSL and ESR signals over Late Pleistocene time scales. pIR-IRSL dose distributions of clast-rich alluvial fan samples are characterised by higher scatter and demonstrate heterogeneous bleaching, while matrix-rich alluvial fan deposits show rather homogeneous poor bleaching in the dose dispersion as indicated by a modern analogue sample. In contrast, marine and aeolian deposits are homogeneously well bleached, supported by a modern littoral sample. Following the quartz multiple centre (MC) ESR dating approach (Al and Ti centres), bleaching of the different centres prior to deposition has been achieved. While the Ti–H centre provides mostly lower doses than the Ti–Li centre, in most cases the Al centre provides the highest dose values. This pattern is consistent with their respective bleaching kinetics and suggests that the Ti centre signals most likely provide the closest estimate to the true burial dose for samples with doses >200 Gy. ESR and pIR-IRSL ages are consistent at 2σ for the marine, aeolian and clast-rich debris-flow deposits, which is in agreement with existing chronological data in this area. It appears that the mode of sediment transport on alluvial fans, either as matrix- or clast-rich flows, plays an important role in sediment bleaching. While clast-rich alluvial fan deposits are likely better bleached, we cannot exclude insufficient bleaching during matrix-rich alluvial fan flows; our dating results suggest that both pIR-IRSL and ESR dating overestimate the true burial age. The combination of pIR-IRSL and MC ESR dating can be considered as a promising tool for deciphering alluvial fan formation over (Late) Pleistocene time scales.

Surface Roughness Estimation in the Orog Nuur Basin (Southern Mongolia) Using Sentinel-1 SAR Time Series and Ground-Based Photogrammetry. Ullmann, Tobias; Stauch, Georg. In Remote Sensing, 12(19), S. 3200-. 2020.

[ Abstract ]
[ DOI ]

This study demonstrates an application-oriented approach to estimate area-wide surface roughness from Sentinel-1 time series in the semi-arid environment of the Orog Nuur Basin (southern Mongolia) to support recent geomorphological mapping efforts. The relation of selected mono- and multi-temporal SAR features and roughness is investigated by using an empirical multi-model approach and selected 1D and 2D surface roughness indices. These indices were obtained from 48 high-resolution ground-based photogrammetric digital elevation models, which were acquired during a single field campaign. The analysis is backed by a time series analysis, comparing Sentinel-1 features to temporal-corresponding observations and reanalysis datasets on soil moisture conditions, land surface temperature, occurrence of precipitation events, and presence and development of vegetation. Results show that Sentinel-1 features are hardly sensitive to the changing surface conditions over none to sparsely vegetated land, indicating very dry conditions throughout the year. Consequently, surface roughness is the dominating factor altering SAR intensity. The best correlation is found for the combined surface roughness index Z-Value (ratio between the root mean square height and the correlation length) and the mean summer VH intensity with an r2 coefficient of 0.83 and an Root-Mean-Square Error of 0.032.

Constraining the timing of palaeosol development in Iranian arid environments using OSL dating. Rashidi, Zakieh; Sohbati, Reza; Karimi, Alireza; Farpoor, Mohammad Hady; Khormali, Farhad; Thompson, Warren; Murray, Andrew. In Quaternary Geochronology, 49, S. 92–100. Elsevier BV, 2019.

[ DOI ]

Late Quaternary environments in the Gobi Desert of Mongolia: Vegetation, hydrological, and palaeoclimate evolution. Yu, Kaifeng; Lehmkuhl, Frank; Schlütz, Frank; Diekmann, Bernhard; Mischke, Steffen; Grunert, Jörg; Murad, Waheed; Nottebaum, Veit; Stauch, Georg; Zeeden, Christian. In Palaeogeography, Palaeoclimatology, Palaeoecology, 514, S. 77–91. Elsevier BV, 2019.

[ DOI ]

Geomorphology of the coastal alluvial fan complex Guanillos, northern Chile. Walk, Janek; Stauch, Georg; Bartz, Melanie; Brückner, Helmut; Lehmkuhl, Frank. In Journal of Maps, 15(2), S. 436–447. Informa UK Limited, 2019.

[ Abstract ]
[ DOI ]

The evolution of alluvial fans on the narrow coastal plain of the Atacama Desert in northern Chile is so far poorly investigated. Therefore, a detailed geomorphological map at a scale of 1:7500 of a coastal alluvial fan complex at Guanillos (21°58′S, 70°10.5′W) is provided as a first step to understand the fan’s morphogenesis. Geomorphological mapping was based on a digital elevation model with a resolution of 2 m generated from Pleiades-1 tri-stereo satellite imagery, derived terrain parameters, and on-site field mapping. The resultant map is used to characterize and categorize the overall morphology of the alluvial fan complex. In particular, linear features constructed by primary alluvial fan processes can be differentiated successfully from those developed by secondary processes. Furthermore, the advanced evolutionary state of the fan complex is revealed. We introduce a morphostratigraphic model comprising the fan’s prograde evolution, dissection, and successive abandonment of surface generations.

A conceptual model for the interpretation of aeolian sediments from a semiarid high-mountain environment since the late glacial. Stauch, Georg. In Quaternary Research, 91(1), S. 24–34. Cambridge University Press, 2019.

[ Abstract ]
[ DOI ]

Different interpretations of accumulation and preservation of aeolian sediments lead to divergent and sometimes contradictory palaeoclimate reconstructions. Although aeolian transport mainly occurs during dry climate, the preservation of the aeolian sediment is a critical factor in many environments in determining the nature of the aeolian sedimentary archive. Analysis of more than 200 optically stimulated luminescence ages for aeolian sands from Tibet shows four different aeolian phases of accumulation. Strong aeolian activity occurred during the last glacial maximum, but hardly any aeolian sediments are preserved. Consequently, the period with the highest aeolian activity is not recorded in the sedimentary record. A phase of aeolian accumulation occurred in the late glacial and the early Holocene. The duration of deposition for this phase is a consequence of the complex topography and an increase in moisture. This phase was punctuated by exceptionally strong accumulation during the Younger Dryas stade. The mid-Holocene is characterised by weak aeolian accumulation and fluvial erosion caused by greater precipitation during the maximum height of the Asian summer monsoon. Aeolian activity resumed in the late Holocene because of drier conditions. The conceptual model provides an approach that can be applied to other mountain and desert margin regions that have limited sediment availability.

Geomorphology of the coastal alluvial fan complex Guanillos, northern Chile. Walk, Janek; Stauch, Georg; Bartz, Melanie; Brückner, Helmut; Lehmkuhl, Frank. In Journal of Maps, 15(2), S. 436–447. 2019.

[ Abstract ]
[ DOI ]

The evolution of alluvial fans on the narrow coastal plain of the Atacama Desert in northern Chile is so far poorly investigated. Therefore, a detailed geomorphological map at a scale of 1:7500 of a coastal alluvial fan complex at Guanillos (21°58?S, 70°10.5?W) is provided as a first step to understand the fan?s morphogenesis. Geomorphological mapping was based on a digital elevation model with a resolution of 2?m generated from Pleiades-1 tri-stereo satellite imagery, derived terrain parameters, and on-site field mapping. The resultant map is used to characterize and categorize the overall morphology of the alluvial fan complex. In particular, linear features constructed by primary alluvial fan processes can be differentiated successfully from those developed by secondary processes. Furthermore, the advanced evolutionary state of the fan complex is revealed. We introduce a morphostratigraphic model comprising the fan?s prograde evolution, dissection, and successive abandonment of surface generations.

Response of lake-catchment processes to Holocene climate variability: Evidences from the NE Tibetan Plateau. Yan, Dada; Wünnemann, Bernd; Zhang, Yongzhan; Long, Hao; Stauch, Georg; Sun, Qianli; Cao, Guangchao. In Quaternary Science Reviews, 201, S. 261–279. Elsevier BV, 2018.

[ DOI ]

Environmental changes during the late Pleistocene and the Holocene in the Gonghe Basin, north-eastern Tibetan Plateau. Stauch, Georg; Lai, Zhongping; Lehmkuhl, Frank; Schulte, Philipp. In Palaeogeography, Palaeoclimatology, Palaeoecology, 509, S. 144–155. Elsevier BV, 2018.

[ DOI ]

Paleolakes in the Gobi region of southern Mongolia. Lehmkuhl, Frank; Grunert, Jörg; Hülle, Daniela; Batkhishig, Ochirbat; Stauch, Georg. In Quaternary Science Reviews, 179, S. 1–23. Elsevier BV, 2018.

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Geochemical imprints of coupled paleoenvironmental and provenance change in the lacustrine sequence of Orog Nuur, Gobi Desert of Mongolia. Yu, Kaifeng; Lehmkuhl, Frank; Diekmann, Bernhard; Zeeden, Christian; Nottebaum, Veit; Stauch, Georg. In Journal of Paleolimnology, 58(4), S. 511–532. 2017.

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In the arid environment, due to the scarcity of a continuous terrestrial archive, lacustrine sequences are often employed as a paleoenvironmental repository. However, numerous spatial and temporal heterogeneities exist concerning previously studied sites in arid central Asia. Furthermore, surveys using a XRF core scanning technique on lacustrine sequences retrieved in hyperarid desert settings are largely rare. Hence, two parallel sediment cores (ONW I; ONW II) were retrieved from Orog Nuur, in the Gobi Desert of Mongolia. Continuous, high-resolution elemental abundances at a 1-cm scanning step size were examined in core ONW II using XRF core scanning. To constrain the data quality, elements with high error margins relative to measured peak areas and those elements/proxies below the significance level during the multivariate statistics are excluded for environmental/provenance implications. Based on multivariate statistical evaluation, the bulk-geochemistry of the core sediments are governed by (1) grain-size composition, (2) authigenic productivity (Ca, Cl, CaCO3) in an alkaline environment, (3) allochthonous organic material (TOC and C/Natomic), and (4) terrigenous input via fluvial inflows, as well as quasi-constant aeolian input through the late Quaternary (Al, Si, K, Ti, and Fe). Disparate source lithotypes, as well as authigenic productivity of the lake system existed before and after Termination I. The Holocene was dominated by a distinct high productivity alkaline environment with more felsic and alkaline input relative to the late Pleistocene. This might be attributed to an increased hydrodynamic strength of riverine inflow and/or intensified erosion and weathering of felsic source rocks in the upper catchment of the Orog Nuur. Therefore, in order to gain a better understanding of the bulk-geochemistry of lake sediments, the coupled provenance and environmental signatures, as well as land surface processes in the catchment need to be systematically discerned. Thus, the XRF core scanning data obtained in this study would have practical and complimentary merit for other lacustrine studies focused on the desert realm across the globe.

Project house water: a novel interdisciplinary framework to assess the environmental and socioeconomic consequences of flood-related impacts. Crawford, Sarah E.; Cofalla, Catrina Brüll nee; Aumeier, Benedikt; Brinkmann, Markus; Classen, Elisa; Esser, Verena; Ganal, Caroline; Kaip, Elena; Häussling, Roger; Lehmkuhl, Frank; Letmathe, Peter; Müller, Anne-Katrin; Rabinovitch, Ilja; Reicherter, Klaus; Schwarzbauer, Jan; Schmitt, Marco; Stauch, Georg; Wessling, Matthias; Yüce, Süleyman; Hecker, Markus; Kidd, Karen A.; Altenburger, Rolf; Brack, Werner; Schüttrumpf, Holger; Hollert, Henner. In Environmental Sciences Europe, 29(1). Springer Science and Business Media LLC, 2017.

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Landscape and climate on the northern Tibetan Plateau during the late Quaternary. Stauch, G.; Schulte, P.; Ramisch, A.; Hartmann, K.; Hülle, D.; Lockot, G.; Diekmann, B.; Nottebaum, V.; Müller, C.; Wünnemann, B.; Yan, D.; Lehmkuhl, F. In Geomorphology, 286, S. 78–92. Elsevier BV, 2017.

[ DOI ]

Characterization of Arctic Surface Morphology by Means of Intermediated TanDEM-X Digital Elevation Model Data. Ullmann, Tobias; Büdel, Christian; Baumhauer, Roland. In Zeitschrift für Geomorphologie, Supplementary Issues, 61(1), S. 3–25. Schweizerbart, 2017.

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The correlation of North-Iranian Late-Pleistocene and Holocene playa sediments to basin geomorphology. Büdel, Christian; Padashi, Seyed Majid; Hoelzmann, Philipp; Fuchs, Markus; Baumhauer, Roland. In Zeitschrift für Geomorphologie, Supplementary Issues, 61(1), S. 77–99. Schweizerbart, 2017.

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Late Pleistocene glaciations at Lake Donggi Cona, eastern Kunlun Shan (NE Tibet): early maxima and a diminishing trend of glaciation during the last glacial cycle.. Rother, Henrik; Stauch, Georg; Loibl, David; Lehmkuhl, Frank; Freeman, Stewart P. H. T. In Boreas, 46(3), S. 503–524. Wiley, 2017.

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Aeolian sediments on the northern Tibetan Plateau. Stauch, Georg. G. Stauch (Hrsg.). 2017.

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Sentinel-1 SAR Data Revealing Fluvial Morphodynamics in Damghan (Iran): Amplitude and Coherence Change Detection. Tobias, Ullmann; Christian, Büdel; Roland, Baumhauer; Majid, Padashi. In International Journal of Earth Science and Geophysics, 2(1). VIBGYOR ePress, 2016.

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Multi-decadal periods of enhanced aeolian activity on the north-eastern Tibet Plateau during the last 2ka. Stauch, Georg. In Quaternary Science Reviews, 149, S. 91–101. Elsevier BV, 2016.

[ DOI ]

A persistent northern boundary of Indian Summer Monsoon precipitation over Central Asia during the Holocene. Ramisch, Arne; Lockot, Gregori; Haberzettl, Torsten; Hartmann, Kai; Kuhn, Gerhard; Lehmkuhl, Frank; Schimpf, Stefan; Schulte, Philipp; Stauch, Georg; Wang, Rong; Wünnemann, Bernd; Yan, Dada; Zhang, Yongzhan; Diekmann, Bernhard. In Scientific Reports, 6(1), S. 25791. 2016.

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Extra-tropical circulation systems impede poleward moisture advection by the Indian Summer Monsoon. In this context, the Himalayan range is believed to insulate the south Asian circulation from extra-tropical influences and to delineate the northern extent of the Indian Summer Monsoon in central Asia. Paleoclimatic evidence, however, suggests increased moisture availability in the Early Holocene north of the Himalayan range which is attributed to an intensification of the Indian Summer Monsoon. Nevertheless, mechanisms leading to a surpassing of the Himalayan range and the northern maximum extent of summer monsoonal influence remain unknown. Here we show that the Kunlun barrier on the northern Tibetan Plateau [{\textasciitilde}36{textdegree}N] delimits Indian Summer Monsoon precipitation during the Holocene. The presence of the barrier relocates the insulation effect 1,000thinspacekm further north, allowing a continental low intensity branch of the Indian Summer Monsoon which is persistent throughout the Holocene. Precipitation intensities at its northern extent seem to be driven by differentiated solar heating of the Northern Hemisphere indicating dependency on energy-gradients rather than absolute radiation intensities. The identified spatial constraints of monsoonal precipitation will facilitate the prediction of future monsoonal precipitation patterns in Central Asia under varying climatic conditions.

Discriminating sediment archives and sedimentary processes in the arid endorheic Ejina Basin, NW China using a robust geochemical approach. Yu, Kaifeng; Hartmann, Kai; Nottebaum, Veit; Stauch, Georg; Lu, Huayu; Zeeden, Christian; Yi, Shuangwen; Wünnemann, Bernd; Lehmkuhl, Frank. In Journal of Asian Earth Sciences, 119, S. 128–144. Elsevier BV, 2016.

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Spatio-temporal pattern of detrital clay-mineral supply to a lake system on the north-eastern Tibetan Plateau, and its relationship to late Quaternary paleoenvironmental changes. Opitz, Stephan; Ramisch, Arne; IJmker, Janneke; Lehmkuhl, Frank; Mischke, Steffen; Stauch, Georg; Wünnemann, Bernd; Zhang, Yongzhan; Diekmann, Bernhard. In CATENA, 137, S. 203–218. Elsevier BV, 2016.

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Influence of HCl pretreatment and organo-mineral complexes on laser diffraction measurement of loess–paleosol-sequences. Schulte, Philipp; Lehmkuhl, Frank; Steininger, Florian; Loibl, David; Lockot, Gregori; Protze, Jens; Fischer, Peter; Stauch, Georg. In CATENA, 137, S. 392–405. Elsevier BV, 2016.

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Late Quaternary Lake Dynamics in the Verkhoyansk Mountains of Eastern Siberia: Implications for Climate and Glaciation History. Diekmann, Bernhard; Pestryakova, Luidmilla; Nazarova, Larisa; Subetto, Dmitry; Tarasov, Pavel E; Stauch, Georg; Thiemann, Arne; Lehmkuhl, Frank; Biskaborn, Boris K; Kuhn, Gerhard; Henning, Denis; Müller, Stefanie. In Polarforschung. Alfred-Wegener-Institut für Polar- und Meeresforschung und Deutsche Gesellschaft für Polarforschung, 2016.

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Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor — An example from northern Chinese drylands. Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg; Lu, Huayu; Yi, Shuangwen. In Geomorphology, 250, S. 113–127. Elsevier BV, 2015.

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Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene–Holocene transition (~12ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (<5700m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene–Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed. Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer consideration of the fluvial influence on aeolian archives in palaeoenvironmental studies from central Asian and other drylands.

Geomorphological and palaeoclimate dynamics recorded by the formation of aeolian archives on the Tibetan Plateau. Stauch, Georg. In Earth-Science Reviews, 150, S. 393–408. Elsevier BV, 2015.

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[ DOI ]

Aeolian sediments are an important archive for palaeoclimate reconstructions on the Tibetan Plateau. The accumulation of aeolian sediments and the formation of palaeosols are used as a proxy for dry and wet phases, respectively. During the last decade the number of OSL (optically stimulated luminescence) ages of aeolian sediments has been rapidly increasing. This study summarises the results from more than 300 individual OSL ages. Despite the widespread occurrence of aeolian sediments on the Tibetan Plateau nearly all OSL samples are located on the northeastern and the southern part. In most regions the strongest accumulation occurred during the late Glacial and in the early Holocene. This coincides with the strengthening of the Asian summer monsoon on the Tibetan Plateau and wetter climate conditions after the relatively dry glacial times. The development of a sufficient vegetation cover, acting as a sediment trap, seems to be an important requirement for the preservation of aeolian archives. Short dry periods like the Younger Dryas led to a more enhanced aeolian accumulation without destruction of previously formed archives in some regions. The formation of palaeosols occurred mainly during the wet early and mid-Holocene, but the number of ages is relatively small. In contrast, a second phase of aeolian accumulation during the late Holocene was related to the weakening of the Asian summer monsoon and drier climate conditions. This indicates that the reaction of aeolian accumulation on the Tibetan Plateau depends on the previous climate state. A comparison between the OSL ages from aeolian sands and loess deposits yields a different timing of deposition of these two sediment types. While the sand deposits in different basins resemble wet and dry phases, loess deposits show no common signal between the analysed areas. This indicates an influence of local factors, such as varying source areas and erosive processes on the slopes. In general, the aeolian archives in the high mountain environment are governed by numerous factors besides the climatic influence.

Seismites as indicators for Holocene seismicity in the northeastern Ejina Basin, Inner Mongolia. Rudersdorf, Andreas; Hartmann, Kai; Yu, Kaifeng; Stauch, Georg; Reicherter, Klaus. In Geological Society, London, Special Publications, 432(1), S. 213–231. Geological Society of London, 2015.

[ DOI ]

Unmixed loess grain size populations along the northern Qilian Shan (China): Relationships between geomorphologic, sedimentologic and climatic controls. Nottebaum, Veit; Stauch, Georg; Hartmann, Kai; Zhang, Jingran; Lehmkuhl, Frank. In Quaternary International, 372, S. 151–166. Elsevier BV, 2015.

[ DOI ]

Effect of Scale and Type of Classification System on the Results of Soil Mapping Using Geopedologic Approach (A Case Study: Damavand Region, Tehran Province). Rashidi, Zakieh. Unpublished, 2015.

[ DOI ]

Effect of Landform’s Type on The Results of Geopedology Approach in Soil Mapping of The Damavand Region. Rashidi, Zakieh. Unpublished, 2015.

[ DOI ]

Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor — An example from northern Chinese drylands. Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg; Lu, Huayu; Yi, Shuangwen. In Geomorphology, 250, S. 113–127. 2015.

[ Abstract ]
[ DOI ]

Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene–Holocene transition (~12ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (<5700m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene–Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed. Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer consideration of the fluvial influence on aeolian archives in palaeoenvironmental studies from central Asian and other drylands.

Timing and spatial distribution of loess and loess-like sediments in the mountain areas of the northeastern Tibetan Plateau. Lehmkuhl, Frank; Schulte, Philipp; Zhao, Hui; Hülle, Daniela; Protze, Jens; Stauch, Georg. In CATENA, 117, S. 23–33. Elsevier BV, 2014.

[ DOI ]

Regional grain size variations in aeolian sediments along the transition between Tibetan highlands and north‐western Chinese deserts – the influence of geomorphological settings on aeolian transport pathways. Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg; Hartmann, Kai; Wünnemann, Bernd; Schimpf, Stefan; Lu, Huayu. In Earth Surface Processes and Landforms, 39(14), S. 1960–1978. Wiley, 2014.

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Sediment distribution is investigated applying grain size analysis to 279 surface samples from the transitional zone between high mountains (Qilian Shan) and their arid forelands (Hexi Corridor) in north-western China. Six main sediment types were classified. Medium scale (103 m) geomorphological setting is carefully considered as it may play an important role concerning sediment supply and availability. A tripartite distribution of sedimentological landscape units along the mountain to foreland transition is evident. Aeolian sediments (e.g. loess and dune sands) are widespread. They are used to identify aeolian transport pathways. The mU/fS-ratio (5–11 µm/48–70 µm) among primary loess opposes the two grain size fractions being most sensitive to varying accumulation conditions. The first fraction is attributed to long-distance transport in high suspension clouds whereas the latter represents local transport in saltation mode. The ratio shows strong correlation with elevation (R2 = 0.77). Thus, it indicates a relatively higher far-traveled dust supply in mountainous areas (>3000 m above sea level [a.s.l.]) compared to the foreland. The contribution of westerlies to high mountain loess deposits is considered likely. Hereby, the influence of the geomorphological setting on grain size composition of aeolian sediments becomes apparent: the contribution from distant dust sources is ubiquitous in the study area. However, the far-distance contribution may be reduced by the availability of fine sand provided in low topography settings. Plain foreland areas support fine sand deflation from supplying river beds, allowing the formation of sandy loess in foreland areas and intramontane basins. In contrast, high mountain topography inhibits strong sand deflation into loess deposits. Eastern parts of the Hexi Corridor show higher aeolian sand occurrence. In contrast, the western parts are dominated by gravel gobi surfaces. This is attributed to higher sand supply in eastern parts provided by the Badain Jaran Desert and fluvial storages as sand sources.

Interaction of geomorphological processes on the north-eastern Tibetan Plateau during the Holocene, an example from a sub-catchment of Lake Donggi Cona. Stauch, Georg; Pötsch, Steffen; Zhao, Hui; Lehmkuhl, Frank. In Geomorphology, 210, S. 23–35. Elsevier BV, 2014.

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[ DOI ]

Abstract Geomorphological landforms on a large alluvial fan and neighboring areas on the eastern side of the Donggi Cona show a complex spatial pattern. Sediment availability is an important factor in the formation of these archives and is partly associated with lake level fluctuation. Different sedimentary archives therefore show a similar geomorphological signal while in some cases similar archives are related to different forcing. The chronology of the processes is based on 22 optical stimulated luminescence (OSL) ages obtained from coarse-grained quartz or potassium-feldspar. The base of the alluvial fan formed during the late Pleistocene but deposition of cover sediments on the fan only started at around 7 ka ago. Silty sediments form a thin cover on the uppermost terraces and have been available only during short timespans. Most of the sediments are sandy deposits which form an internal sediment cycle on the fan. They developed throughout the Holocene. Sandy deposits on the footslopes of the neighboring hills have been preserved since the Pleistocene-Holocene transition. Thicker eolian deposits accumulated during the late Holocene. These sediments were washed into the Donggi Cona and formed sandy lake sediments which were susceptible to remobilization during lower lake levels. In combination with drier climatic conditions during the late Holocene these sediments formed small dunes on the fan. Sediments on the alluvial fan are highly active, for which erosion and deposition vary in space and time. The interaction of fluvial and eolian processes is an important part of this dynamic high mountain system.

Early to mid-Holocene lake high-stand sediments at Lake Donggi Cona, northeastern Tibetan Plateau, China. Dietze, Elisabeth; Wünnemann, Bernd; Hartmann, Kai; Diekmann, Bernhard; Jin, Huijun; Stauch, Georg; Yang, Sizhong; Lehmkuhl, Frank. In Quaternary Research, 79(3), S. 325–336. Cambridge University Press, 2013.

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Lake high-stand sediments are found in three onshore terraces at Lake Donggi Cona, northeastern Tibetan Plateau, and reveal characteristics of hydrological changes on lake shorelines triggered by climate change, geomorphological processes, and neo-tectonic movements. The terraces consist of fluvial–alluvial to littoral-lacustrine facies. End-member modeling of grain-size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition. Radiocarbon dating revealed higher than modern lake levels during the early and mid Holocene. Lake levels follow the trend of Asian monsoon dynamics, and are modified by local non-climatic drivers. Site-specific impacts explain fluctuations during the initial lake-level rise ~ 11 cal ka BP. Maximum lake extension reached ~ 9.2 cal ka BP, at ~ 16.5 m above present lake level (a.p.l.l.). Littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post-depositional cryoturbations at ~ 8.5 cal ka BP, when the lake level fell to ~ 8 m a.p.l.l. After a second maximum at ~ 7.5 cal ka BP, lake level declined slightly at ~ 6.8 cal ka BP, probably due to a non-climatic pulse that caused lake opening. The level remained high until a transition towards drier conditions ~ 4.7 cal ka BP. Though discontinuous, high-stand sediments provide a unique, high-resolution archive.

Characterisation of transport processes and sedimentary deposits by statistical end-member mixing analysis of terrestrial sediments in the Donggi Cona lake catchment, NE Tibetan Plateau. IJmker, Janneke; Stauch, Georg; Dietze, Elisabeth; Hartmann, Kai; Diekmann, Bernhard; Lockot, Gregori; Opitz, Stephan; Wünnemann, Bernd; Lehmkuhl, Frank. In Sedimentary Geology, 281, S. 166–179. Elsevier BV, 2012.

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Abstract Unmixing of grain-size distributions with multivariate statistical analysis gives indications of the main sediment transport processes and related environmental conditions in an area. We performed end-member mixing analysis (EMMA) of sedimentological data from 912 terrestrial sediment samples collected in the Donggi Cona catchment, north-eastern Tibetan Plateau. Up to the present, this is the largest sedimentological dataset on the Tibetan Plateau. EMMA resulted in the characterisation of three end-members that explain 88% of the variance within the dataset. The end-members all represent aeolian deposits. The first end-member EM 1 represents very fine dune sediments that were deflated from a former lake system. EM 2 represents medium sand deposits that were blown out from playa and alluvial fan sediments. EM 3 represents fine loess(− like) sediments mainly found at higher elevations. Different transformations, adding of a fourth end-member and adding of up to 200 loess samples do not change the composition of the end-members, demonstrating the robustness of the model. EMMA allows the synchronous interpretation of very large datasets, resulting in a general characterisation of sediment transport in a particular area. Performing EMMA on the dataset demonstrates the importance of aeolian transport in this part of the world.

Aeolian sediments on the north-eastern Tibetan Plateau. Stauch, Georg; IJmker, Janneke; Pötsch, Steffen; Zhao, Hui; Hilgers, Alexandra; Diekmann, Bernhard; Dietze, Elisabeth; Hartmann, Kai; Opitz, Stephan; Wünnemann, Bernd; Lehmkuhl, Frank. In Quaternary Science Reviews, 57, S. 71–84. Elsevier BV, 2012.

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Aeolian sediments on the Tibetan Plateau are an important archive of palaeoclimatic information. This study presents a detailed analysis of sediments from the Donggi Cona catchment on the north-eastern part of the Tibetan Plateau. Long- and short-distance sediment transport leads to a complex pattern of aeolian sediment deposition that depends on climatic changes as well as on the availability of sediments. Based on the largest dataset of OSL datings (51) from a single catchment on the Tibetan Plateau so far, different periods of increased sediment transport have been reconstructed. Increased aeolian deposition in this high elevation environment started in the early Holocene with the accumulation of sands from around 10.5 to 7 ka. Loess sediments have been preserved from a period from 10.5 to 7.5 ka. Both archives are related to the strengthening of the Asian summer monsoons characterized by wetter and warmer climate. This change in climate supported the trapping of aeolian sediments. Under full monsoon conditions from around 9 ka onwards fluvial processes resulted in erosion of the aeolian archives and the formation of colluvial sediments until 6 ka. A dry and cooler climate resulted in the reactivation of dune sands from 3 ka to present, possibly in combination with stronger human influence. Aeolian sediments on the Tibetan Plateau therefore indicate two different climatic modes. During the early Holocene wetter conditions were favourable to retain aeolian sediments. The reactivation of sediment in the late Holocene due to small-scale disturbances in the vegetation cover, points to a cooler and drier climate.

Dry periods on the NE Tibetan Plateau during the late Quaternary. IJmker, Janneke; Stauch, Georg; Pötsch, Steffen; Diekmann, Bernhard; Wünnemann, Bernd; Lehmkuhl, Frank. In Palaeogeography, Palaeoclimatology, Palaeoecology, 346–347, S. 108–119. Elsevier BV, 2012.

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Environmental conditions on the Tibetan Plateau are changing rapidly. This study reconstructs late Quaternary environmental changes on the northeastern Tibetan Plateau based on sand deposits. The study area is located close to the present maximum extent of the East‐Asian summer monsoon and is likely to register shifts in monsoon extent. Furthermore, different sediment deposits are available that allow reconstruction of sediment pathways between the different archives. Sediment deposition in the catchment is dominated by deposition of sand. Sandy deposits in the form of dune fields and sand sheets are widespread on the northeastern Tibetan Plateau and are an important archive for paleoclimatic reconstruction. This study shows that sand deposits on the northeastern Tibetan Plateau are local phenomena that still bear the sedimentological and geochemical fingerprint of their source materials. Reconstruction of transport processes in the local sediment cascade shows that local sand deposits are the main source of Tibetan mountain loess. Six long sections were sampled and analysed for their geochemical and sedimentological characteristics, showing that both sand and loess deposits have a local source. A special focus was placed on the manganese concentration and the related environmental implications. In several sections, an increase in Mn concentration from 318 ± 44 to 878 ± 294 ppm was found, independent of concentrations in Fe and organic compounds. Since the increase in Mn is caused by solid Mn3+ and Mn4+ alone, it is interpreted as increased dust input. The synchronicity with climatic variations on the northeastern Tibetan Plateau confirms the climatic interpretation of the variations in Mn. Sand and dust transport both took place around 11 ka, followed by a period of fixation or even erosion of sediments. Although increased sand transport in the catchment already started around 3 ka, the increased dust input did not take place before 0.7 ka. Therefore, the Mn concentrations are interpreted as an indication of increased dust transport during the very late Holocene, related to colder and drier circumstances during that time. The use of manganese as a proxy for dust is a valuable addition to the toolbox of paleoclimate reconstruction, since it is a direct proxy of dust in deposits. However, further validation and testing should be performed before general acceptation of Mn as a paleoclimate proxy in terrestrial sediments.

Late Glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis. Opitz, Stephan; Wünnemann, Bernd; Aichner, Bernhard; Dietze, Elisabeth; Hartmann, Kai; Herzschuh, Ulrike; IJmker, Janneke; Lehmkuhl, Frank; Li, Shijie; Mischke, Steffen; Plotzki, Anna; Stauch, Georg; Diekmann, Bernhard. In Palaeogeography, Palaeoclimatology, Palaeoecology, 337–338, S. 159–176. Elsevier BV, 2012.

[ Abstract ]
[ DOI ]

Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19 kyr. The lake today fills a 30 × 8 km big and 95 m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatio-temporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system. The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39 m below the present level and started to rise after 19 ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13 cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3 cal ka BP, grain-size fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2 m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early to mid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3 cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base.

Environmental conditions in the Donggi Cona lake catchment, NE Tibetan Plateau, based on factor analysis of geochemical data. IJmker, Janneke; Stauch, Georg; Hartmann, Kai; Diekmann, Bernhard; Dietze, Elisabeth; Opitz, Stephan; Wünnemann, Bernd; Lehmkuhl, Frank. In Journal of Asian Earth Sciences, 44, S. 176–188. Elsevier BV, 2012.

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We present a methodological approach for the characterization of spatial variations of environmental and transport conditions based on geochemical data. We analyzed the geochemical characteristics of terrestrial sediments on an alluvial fan and adjacent areas in the eastern part of the Donggi Cona catchment. The geochemical characteristics of the sediment samples were measured using X-ray fluorescence spectroscopy. A factor model based on nine elements (Sr, Rb, Zn, Fe, Mn, V, Ti, Ca and K) gave the best results using factor analysis. Our results show that factor analysis of geochemical data can explain spatial variations in the catchment, even within a relatively small area with more or less constant climatological conditions. The four most important factors of our model explain 68.4% of the total variance within the dataset. The four factors represent a carbonate, weathering and two redox condition signals, respectively. The spatial distribution of factor loadings points to regions with specific environmental conditions. These regions show a certain carbonate input or production (factor 1), specific weathering rates (factor 2) or specific redox conditions (factors 3 and 4). The factor loadings of the first and second factor are used to reclassify the data into four groups, being dune, loess, lake and fluvial gravel sediments. This reclassification confirms or improves the prior field classification in 70% of all cases. For 23% of the samples, the model gave a different interpretation. The factor loadings in these cases represent the origin of the material rather than its present sediment type, thereby giving valuable information about sediment provenance. Since the third and fourth factor seem more dependent on location, they do not differentiate between different sediment types. Multivariate statistics of the geochemistry of terrestrial sediments (i) allows the subdivision of samples into different sediment types, (ii) indicates dominant regions for weathering, carbonate production and manganese washout and (iii) gives suggestions about the provenance of the sediments. This is the first detailed study of geochemical parameters on the Tibetan Plateau not focusing on lake cores, resulting in a spatial characterization of the local geochemistry. This gives insight in the sediment transport connections between the catchment and the lake, illustrating the value of terrestrial sediments as additional indicator of environmental variations.

An end-member algorithm for deciphering modern detrital processes from lake sediments of Lake Donggi Cona, NE Tibetan Plateau, China. Dietze, Elisabeth; Hartmann, Kai; Diekmann, Bernhard; IJmker, Janneke; Lehmkuhl, Frank; Opitz, Stephan; Stauch, Georg; Wünnemann, Bernd; Borchers, Andreas. In Sedimentary Geology, 243–244, S. 169–180. Elsevier BV, 2012.

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Deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes. One approach going beyond classical methods is the unmixing of grain-size distributions. This paper presents a flexible end-member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties. It has been applied to the detrital grain-size components of lacustrine surface sediment samples of Lake Donggi Cona, Qinghai Province, China. It allows up to five grain-size end-members to be characterised and quantified in an optimal model. An end-member with a major mode in the clay domain accounts for 34% of variance within the grain-size data set. It may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer. Three end-members in the fine sand to medium silt domains make up 60% of lacustrine sedimentation. They may represent local to remote aeolian processes that peak in wintertime. A multimodal end-member explaining the remaining 6% of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors. Several model runs of different scaling and numbers of end-members provided a suitable way to determine uncertainties inherent to the model. A comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end-members. The clay and medium silt end-members are robust features of detrital sedimentation within Lake Donggi Cona. They alone explain 54.4% of total variance in the data. However, no spatial pattern or relation to water depth is found for any of the grain-size end-members. Thus, when past detrital sedimentation at Lake Donggi Cona is reconstructed, a special focus should be on the robust features attributed to aeolian and suspension-related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes. Further applications of the end-member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability.

Global, regional and local scale factors determining glaciation extent in Eastern Siberia over the last 140,000 years. Krinner, Gerhard; Diekmann, Bernhard; Colleoni, Florence; Stauch, Georg. In Quaternary Science Reviews, 30(7–8), S. 821–831. Elsevier BV, 2011.

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The aim of this work is to evaluate the effect of variations of greenhouse gas concentrations, orbital parameters, sea-surface conditions, vegetation and dust deposition on the extent of East Siberian mountain glaciations during the late Quaternary. An atmosphere-only general circulation model is used in a series of 16 sensitivity tests at high spatial resolution over the region of interest to systematically evaluate the relative importance of these different forcing parameters. No attempt was made to reproduce in detail the history of late Quaternary mountain glaciations in East Siberia, because, given (a) the temporal and spatial scarcity of available evidence of mountain glaciations in this region and (b) the large uncertainties concerning the boundary conditions to be prescribed in this model, such an exercise must necessarily remain incomplete and partially inconclusive. The results of this study suggest that moisture delivery from the Atlantic is an important factor determining mountain glacier mass balance in Eastern Siberia and is very sensitive to the geometry of the West Eurasian ice sheet. This means that variable moisture blocking by the West Eurasian ice sheet during the Weichselian is the most important single factor explaining the opposite history of glacier and ice sheet extent in West and East Eurasia during the Weichselian. This work confirms earlier results showing that the large 140kyrBP West Eurasian ice sheet caused regional-scale cooling extending towards Eastern Eurasia. Nevertheless, the simulated response of the regional summer temperature (and thus glacier extent because of the strong dependency of glacier mass balance of summer melt rates) is to a very large extent directly determined by insolation. For the Early Weichselian, this leads to a clear maximum of local glacier extent at 70kyrBP, which is in line with the variations of top-of-the-atmosphere insolation on orbital time scales, but to some degree at odds with geological evidence which suggests larger glacier extent at 115 and 90kyrBP than at 70kyrBP. Through snow feedbacks, the effects of changes in the prescribed vegetation distribution and dust deposition rate are also substantial. In summary, it appears that the broad features of late Quaternary glaciation history in Eastern Eurasia can be understood in terms of known forcings.

Basin morphology and seismic stratigraphy of Lake Donggi Cona, north-eastern Tibetan Plateau, China. Dietze, E.; Wünnemann, B.; Diekmann, B.; Aichner, B.; Hartmann, K.; Herzschuh, U.; IJmker, J.; Jin, H.; Kopsch, C.; Lehmkuhl, F.; Li, S.; Mischke, S.; Niessen, F.; Opitz, S.; Stauch, G.; Yang, S. In Quaternary International, 218(1–2), S. 131–142. Elsevier BV, 2010.

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Basin morphology and depositional stratigraphy of Lake Donggi Cona on the north-eastern Tibetan Plateau has been studied with echo depth sounding and shallow seismic sub-bottom profiling. The basin is a pull-apart structure situated at the highly active Kunlun fault. It is characterised by a 92 m deep graben structure in the western part of the lake basin, and a shallow eastern lake part, the latter filled up with fluvial sediments from a large alluvial plain. Three prominent morphological levels were identified at 24 m, 39 m and 57 m below present lake level. They were partly created by basin subsidence, while the deposition of prograding delta sediments primarily formed the morphological steps. The inherited tectonic structures control on-going neotectonic activity, which seems to have only minor influence on present basin morphology. The basin is filled by sediments of at least 30 m thickness in the depocentre. Three major depositional units can be distinguished. In comparison with lithological changes in a sediment core, they give evidence of pronounced lake-level fluctuations and dramatic changes in lake volume. A numerical age datum of ∼19 cal ka BP at the base of the sediment core allows a tentative reconstruction of Late Glacial to Holocene lake development. A very low base level preceded a time of delta formation during higher lake level, i.e. ∼26 m lower than present during Last Glacial Maximum, creating a lake of only 18% of its present size. At the transition to Holocene the lake-level rose very quickly changing to a deep lake environment. Thus, transgression may have promoted maximum lake stands.

Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia. Stauch, Georg; Lehmkuhl, Frank. In Quaternary Research, 74(1), S. 145–155. Cambridge University Press, 2010.

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Geomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50 ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90 ka, moraine IV is 100 to 120 ka, and the outermost moraine V was deposited around 135 ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets.

Late Quaternary glaciations in northeastern Russia. Stauch, G.; Gualtieri, L. In Journal of Quaternary Science, 23(6–7), S. 545–558. Wiley, 2008.

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A summary of the extent and chronology of Quaternary glaciations in NE Russia is presented in this paper. The complex timing and style of glaciations include asynchronous development of alpine glaciers in the western and eastern part of the area. While in the eastern part of NE Russia well-preserved moraines have been dated to the global Last Glacial Maximum (18–24 ka), in the westernmost part of the area no glacial advance took place at this time. In general, glacial advances were more extensive earlier rather than later, in the last glacial cycle. Although only a handful of studies with reliable absolute ages in the vast area of NE Russia exist, it is clear that the number of advances throughout the region varies. Variable glacial response to global climate patterns is attributable to contrasting sources of precipitation. An Atlantic moisture source dominates in the western part of NE Russia, while a Pacific source influences the eastern part of the region. The glacial advances in the interior of NE Russia are largely unexplored and further research is needed in order to understand Quaternary climate change in the region.

Sediment provenance of late Quaternary morainic, fluvial and loess‐like deposits in the southwestern Verkhoyansk Mountains (eastern Siberia) and implications for regional palaeoenvironmental reconstructions. Popp, Steffen; Belolyubsky, Innokenty; Lehmkuhl, Frank; Prokopiev, Andrei; Siegert, Christine; Spektor, Valentin; Stauch, Georg; Diekmann, Bernhard. In Geological Journal, 42(5), S. 477–497. Wiley, 2007.

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Abstract A provenance analysis of late Quaternary deposits from tributaries of the Aldan and Lena rivers in Central Yakutia (eastern Siberia) was carried out using analysis of heavy minerals and clay mineralogy. Cluster analysis revealed one assemblage that is characterized by relatively high proportions of amphibole, orthopyroxene and garnet as well as pedogenic clay minerals, reflecting a sediment provenance from the wide catchment area of the Lena and Aldan rivers. In contrast, the three other clusters are dominated by stable heavy minerals with varying amounts of clinopyroxene, apatite and garnet, as well as high percentages of illite and chlorite that are indicative of source rocks of the Verkhoyansk Mountains. Glacial moraines reveal the local mountain source signal that is overprinted by the Lena-Aldan signal in the oldest moraines by reworking processes. Alluvial sediments in the Verkhoyansk Foreland show a clear Lena source signal through intervals of the middle and late Pleistocene, related to a stream course closer to the mountains at that time. Loess-like cover sediments are characterized by the dominant Lena provenance with increasing proportions of local mountain sources towards the mountain valleys. Aeolian sands in an alluvial terrace section at the mountain margin covering the time between 30?ka and 10?ka BP reflect temporarily dominant inputs of aeolian materials from the Lena Plains.

Luminescence chronology from the Verkhoyansk Mountains (North-Eastern Siberia). Stauch, G.; Lehmkuhl, F.; Frechen, M. In Quaternary Geochronology, 2(1–4), S. 255–259. Elsevier BV, 2007.

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This study presents new dating results from the Verkhoyansk Mountains in northeastern Siberia. Pleistocene sediments of aeolian and glacial origin have been studied and dated by infrared optically stimulated luminescence (IRSL). The chronostratigraphy of this vast area is mainly based on radiocarbon dating up to now. Aeolian sediments are widespread in the foreland of the Verkhoyansk Mountains. IRSL-dating results indicate two major periods of increased accumulation between 33 and 24ka and between 13 and 9ka. A new stratigraphy of Pleistocene glaciations in this area has been developed. Up to five end moraines have been identified in two catchments areas. IRSL was applied to date the sandy and silty sediments covering the glacial deposits in order to get minimum ages. Furthermore, glacial and glacio-fluvial deposits were also sampled from a few locations. According to the IRSL dating results, the uppermost end moraine was deposited prior to 50ka. The three outermost moraines might have been formed during Early Weicheslian to Saalian times. It is very likely that no major glaciers reached the foreland of the Verkhoyansk Mountains during the Last Glacial Maximum (LGM, MIS 2).

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