Publications - Chair of Geomorphology

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.

[ Abstract ]
[ DOI ]

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.

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ DOI ]

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

Abstract Background The reconstruction of the pollution history using aquatic sedimentary archives is of major relevance not only for the present and past, but also for future actions. The extent and influence of past anthropogenic emissions can be correlated with site-specific (e.g., industrial) developments as well as political actions, regulations, and initiatives. Finally, the need for further restrictions, specific monitoring or other countermeasures can be defined. Accordingly, within the scope of this study, a drilling core of subaquatic sediment was comprehensively analyzed to reconstruct the pollution history of the Urft reservoir and to understand the linkage between introduction, fate, and behavior of different organic pollutants. Results The Urft reservoir is well suitable for pollution reconstruction as the investigated interval covered a period of nearly 60 years of undisturbed sedimentation of fine-grained material. Additionally, specific input factors and their development (e.g., in industrial production) could be easily correlated with the emission profile detected for the reservoir. Overall, quantitative data of more than 60 lipophilic organic compounds were obtained and traced back to urban and industrial emissions. Concentrations were mainly in the range of ng/gTOC–µg/gTOC showing a decreasing tendency toward the surface and, thus, the effectiveness of political regulations. In addition, a clear maximum was detected for almost all substances at the end of the 1970s/beginning of the 1980s, probably related to an exceptional event such as a flood or a malfunction affecting wastewater-related compounds of both urban and industrial origin. Conclusions Based on the organic-geochemical investigation and the associated dating, it was possible to reconstruct the pollution history of the Urft catchment in the northern Eifel mountains. Overall, organic indicators have proven to be very useful to obtain information on distribution patterns and the influence of industrial as well as governmental actions. For instance, catchment-specific developments such as the closure of ironworks were recognizable in the identified emission patterns. Generally, in the last 50 years, the pollution of the reservoir sediment has decreased clearly showing the efficiency of increasing environmental awareness and corresponding regulations.

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.

[ Abstract ]
[ DOI ]

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.

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.

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.

[ Abstract ]
[ DOI ]

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.

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

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

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

[ Abstract ]
[ DOI ]

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.

Picture credits