Georg Stauch

The extent of Late Pleistocene glaciations in the Altai and Khangai Mountains

Summary The current state of research concerning the extent of Late Pleistocene glaciations in Mongolia and the Russian Altai is summarised. Pleistocene moraines resulting from valley glaciers, plateau glaciers, cirque glaciers and ice streams can be found. The most extensive Late Pleistocene glaciation occurred in the western part of the Altai. However, the extent of Late Pleistocene ice in the Russian Altai is still under debate. In the eastern Altai and especially in the northern part of the Mongolian Altai, Pleistocene glaciers were restricted to several isolated mountain systems. To show the variations in the ice extent, the modern and Late Pleistocene equilibrium-line altitudes (ELAs) and the glaciated area are presented in two cross-sections through the Altai and Western Mongolia. The ELAs are relatively low in the more humid outermost ranges of the arid and semi-arid regions of Central Asia and rise towards the central part of Mongolia. The limited extent of present and Pleistocene glaciers in the eastern part of the Russian Altai and in the Mongolian Altai is the result of decreasing precipitation from west to east. This results in a rise of both the present-day and Pleistocene ELAs towards the east. However, it was more pronounced during the Pleistocene than today. There is an essential lack of absolute dating of glacial sediments in this particular region. Nevertheless, on the basis of present knowledge, most Late Pleistocene glacier advances in Mongolia and in the Russian Altai took place during Marine Isotope Stages (MIS) 2 and 4.

Chapter 69 – The Extent and Timing of Late Pleistocene Glaciations in the Altai and Neighbouring Mountain Systems

Abstract Late Pleistocene glaciations for Mongolia and the Russian Altai are summarized. Whereas an ice sheet occurs in the western Russian Altai, the Pleistocene glaciers have been restricted to several isolated mountain systems in the eastern part of the Altai. Most Late Pleistocene glacier advances took place in the MIS 2 and 4.

A persistent northern boundary of Indian Summer Monsoon precipitation over Central Asia during the Holocene

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

Geochemical imprints of coupled paleoenvironmental and provenance change in the lacustrine sequence of Orog Nuur, Gobi Desert of Mongolia

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

Seismites as indicators for Holocene seismicity in the northeastern Ejina Basin, Inner Mongolia

Abstract This paper contributes to the understanding of palaeoseismology in slowly deforming regions by demonstrating the interpretation of soft-sediment deformation to be a valuable tool in identifying palaeoseismicity where the present-day seismicity is low and the geomorphology initially does not indicate active tectonics by the presence of fault scarps, surface ruptures or diverted rivers. The Ejina Basin (also known as the Gaxun Nur Basin or Juyan Lake Basin) in Inner Mongolia exhibits highly variable endorheic lakes, such as the Late Quaternary Juyanze Palaeolake. We assessed the Holocene tectonic activity of the Western Juyanze Palaeolake Basin, situated within the Ejina Basin, by identifying seismites and a previously unknown normal fault. Deformation mechanisms other than earthquakes, such as landslides or cryoturbation in permafrost, can be excluded. Far-field and near-field seismic sources are considered to have generated the soft-sediment deformation structures. As the occurrence of seismites is restricted to the Western Juyanze Palaeolake Basin and there is Pleistocene–Holocene activity on the Tienehu Fault, a near-field source is most likely.

Project house water: a novel interdisciplinary framework to assess the environmental and socioeconomic consequences of flood-related impacts

Protecting our water resources in terms of quality and quantity is considered one of the big challenges of the twenty-first century, which requires global and multidisciplinary solutions. A specific threat to water resources, in particular, is the increased occurrence and frequency of flood events due to climate change which has significant environmental and socioeconomic impacts. In addition to climate change, flooding (or subsequent erosion and run-off) may be exacerbated by, or result from, land use activities, obstruction of waterways, or urbanization of floodplains, as well as mining and other anthropogenic activities that alter natural flow regimes. Climate change and other anthropogenic induced flood events threaten the quantity of water as well as the quality of ecosystems and associated aquatic life. The quality of water can be significantly reduced through the unintentional distribution of pollutants, damage of infrastructure, and distribution of sediments and suspended materials during flood events. To understand and predict how flood events and associated distribution of pollutants may impact ecosystem and human health, as well as infrastructure, large-scale interdisciplinary collaborative efforts are required, which involve ecotoxicologists, hydrologists, chemists, geoscientists, water engineers, and socioeconomists. The research network “project house water” consists of a number of experts from a wide range of disciplines and was established to improve our current understanding of flood events and associated societal and environmental impacts. The concept of project house and similar seed fund and boost fund projects was established by the RWTH Aachen University within the framework of the German excellence initiative with support of the German research foundation (DFG) to promote and fund interdisciplinary research projects and provide a platform for scientists to collaborate on innovative, challenging research. Project house water consists of six proof-of-concept studies in very diverse and interdisciplinary areas of research (ecotoxicology, water, and chemical process engineering, geography, sociology, economy). The goal is to promote and foster high-quality research in the areas of water research and flood-risk assessments that combine and build off-laboratory experiments with modeling, monitoring, and surveys, as well as the use of applied methods and techniques across a variety of disciplines.

Lake-System Response to Late Quaternary Environmental Dynamics onthe northeastern Tibetan Plateau

Palaeoclimatic reconstructions in central China often rely on proxy information, obtained from single palaeoenvironmental archives at a distinct study site, such as lake sediments. Although they provide a high temporal resolution of information, their context within the acting depositional and geomorphological processes in a distinct landscape unit often is difficult to ascertain. The nature of lake systems strongly depends on catchment processes in addition to direct responses to climate forcing. In the scope of palaeoclimatic studies on the northern Tibetan Plateau and its foreland, we investigate the complex interaction of landscape evolution in response to monsoon dynamics. Our approach follows a source-to-sink approach along sediment cascades, to infer palaeoclimatic responses and to decipher internal non-climatic dynamics of the landscape system. Lake sediments represent the final and mostly complete sedimentary products, while adjacent landforms and offshore deposits provide insights into the spatial dimension of palaeoenvironmental change. The approach of concerted geomorphological and limnogeological research was successfully demonstrated at Lake Donggi Cona on the NE Tibetan Plateau at 4,090 m elevation. The 30 km long, 8 km wide, and 90 m deep lake occupies a pull-apart basin. Sub-bottom profiling revealed the presence of tectonic structures as well as subaquatic terraces and ancient fan systems from former low lake stands, draped by younger lake sediments. A prominent moraine arc in the vicinity of the lake can be attributed to a glacial advance during an early stage of the last glacial cycle. Several terrace levels and fossil lake sediments of early to mid-Holocene age around the lake shore document former stages of higher lake level of about 10 m above present level. In addition to alluvial processes, dunes and loess-like sediments in the catchment of the lake give evidence of differing stages in the intensity of aeolian sediment mobilisation or fixation. Lake development is documented by multi-proxy data in a series of sediment cores across the lake basin. The oldest recovered sediments, younger than 18 ka BP, comprise siliciclastic laminates and lateglacial saline shallow-lake sediments, overlying basal sands. The deposition of fine-grained marls and enhanced biological production characterized the deep lacustrine environment of the Holocene. A switch from a closed lake basin with brackish conditions towards an open oligotrophic fresh-water basin after 6.8 ka BP is indicated by ostracod assemblages and changes in carbonate chemistry. This change in hydrology likely was triggered by tectonic pulses along the Kunlun Fault, an area with severe earthquake activity. Pollen records exhibit climate signals and indicate moist conditions in the early Holocene. During the same time, loess sediments have been preserved from a period from 10.5 to 7.5 ka BP, related to the strengthening of the insolation-driven Asian summer monsoons. This time was characterized by wetter and warmer climate and supported the trapping of dust. A dry and cooler climate resulted in the reactivation of dune sands from 3 ka to present, possibly in combination with stronger human influence.

Aeolian transport pathways along the transition from Tibetan highlands towards northwestern Chinese deserts

Grain size analysis of 279 surface sediment samples from the transition of Tibetan highlands (Qilian Shan) towards northwestern Chinese deserts allows the differentiation of contributing pathways among three types of aeolian sediments: silty loess, sandy loess, and aeolian sands. The study area exhibits a high diversity of geomorphological surfaces due to varieties in relief, elevation and climatic conditions. Therefore, it provides the opportunity to investigate the characteristics of sediments in different geomorphological settings. Using the peaks of grain size frequency’s standard deviation of primary loess allows identification of the most sensitive fractions to varying accumulation conditions. mU/fS-ratio (7 – 13 μm / 58 – 84 μm) of primary silty loess relates the far-travelled dust proportion to the locally transported fine sand component. In vicinity to fluvial channels in the foreland mU/fSvalues are significantly decreased, whereas mU/fS-values increase with altitude (r = 0.74). This indicates higher contribution of long distance transport compared to lower regions. A prominent increase of mU/fS-values above 3000 m asl likely indicates an increasing contribution of fine and medium silt particles transported by Westerlies in higher altitudes. In contrast, lower areas seem to be more strongly influenced by low altitude monsoon currents (NW-Winter/ SE-summer monsoon). The difference in grain size properties is additionally enhanced by the contrasting geomorphologic settings along the mountain declivity: Plain foreland alluvial fans support fine sand supply and availability whereas steep high mountain topography provides only limited potential for fine sand deflation. Similarly, the relatively low relief in intramontane basins leads to fluvial sediment aggradation and allows comparably high fine sand deflation. This supports the formation of sandy loess in these regions and on foreland alluvial fans, whereas in contrast, sandy loess is absent in the high mountain geomorphologic setting.