Jungquartäre Landschafts- und Klimageschichte der Südmongolei

In palaeoclimate research concerning central Asia, up to now the focus was set on regions as Russia, northern Mongolia and China. Therefore only a few palaeoclimatic data are pub-lished on southern Mongolia. In order to understand the climatic development of central Asia and to get an impression of future environmental conditions, information on minor in-vestigated areas are important. This study sets focus on palaeoclimate and the sedimentological and morphological processes of two catchment areas of southern Mongolia (Orog Nuur, Bayan Tohomiin Nuur). The multiparameter analysis of three sediment cores yields information to reconstruct lake level changes, processes of transport, sedimentation and weathering during the last 50ka within the catchment of the lakes. Optical stimulated luminescence (OSL) data from selected sections (fluvial and aeolian sediments) give additional information on palaeoenvironmental conditions of the drainage area. Investigations on terrace sections hint towards cold and arid conditions during 150-120ka. Between 80-70ka a warm and humid climate cloud be recon-structed from lake transgressions. The sedimentological analysis of the lacustrine cores indi-cate low lake levels, accompanied by several phases of increased aeolian activity during 50ka and 13ka, pointing towards predominantly arid and cold climatic conditions. During 35-26ka a change towards a more humid climate could be reconstructed by a lake transgression, accompanied by declining aeolian sedimentation. The proxy data show a more warm and humid climate during the onset of the Holocene (13-11ka). A maximum of temperature and moisture occurred during 9-6ka, interrupted by several short time drying events. Within the investigation area a trend of aridization and remobilization of dune sand can be observed since 6ka. This study offers the first continuous set of palaeoclimatic data from southern Mongolia. The results show a general consistence to adjacent investigation areas of central Asia. Yet, more palaeoclimatic archives from southern Mongolia are required to understand the complex development of climate during the late Quaternary

Jungquartäre Landschafts- und Klimageschichte der Südmongolei

In palaeoclimate research concerning central Asia, up to now the focus was set on regions as Russia, northern Mongolia and China. Therefore only a few palaeoclimatic data are pub-lished on southern Mongolia. In order to understand the climatic development of central Asia and to get an impression of future environmental conditions, information on minor in-vestigated areas are important. This study sets focus on palaeoclimate and the sedimentological and morphological processes of two catchment areas of southern Mongolia (Orog Nuur, Bayan Tohomiin Nuur). The multiparameter analysis of three sediment cores yields information to reconstruct lake level changes, processes of transport, sedimentation and weathering during the last 50ka within the catchment of the lakes. Optical stimulated luminescence (OSL) data from selected sections (fluvial and aeolian sediments) give additional information on palaeoenvironmental conditions of the drainage area. Investigations on terrace sections hint towards cold and arid conditions during 150-120ka. Between 80-70ka a warm and humid climate cloud be recon-structed from lake transgressions. The sedimentological analysis of the lacustrine cores indi-cate low lake levels, accompanied by several phases of increased aeolian activity during 50ka and 13ka, pointing towards predominantly arid and cold climatic conditions. During 35-26ka a change towards a more humid climate could be reconstructed by a lake transgression, accompanied by declining aeolian sedimentation. The proxy data show a more warm and humid climate during the onset of the Holocene (13-11ka). A maximum of temperature and moisture occurred during 9-6ka, interrupted by several short time drying events. Within the investigation area a trend of aridization and remobilization of dune sand can be observed since 6ka. This study offers the first continuous set of palaeoclimatic data from southern Mongolia. The results show a general consistence to adjacent investigation areas of central Asia. Yet, more palaeoclimatic archives from southern Mongolia are required to understand the complex development of climate during the late Quaternary

Holocene geomorphological processes and soil development as indicator for environmental change around Karakorum, Upper Orkhon Valley (Central Mongolia)

Mantles of silt- and sand-size particles, paleosols and fluvial deposits preserve valuable information on Holocene environmental change. These archives were used to reconstruct the landscape history in the upper Orkhon Valley close to the former capitals of the Uighurs (Kharbalgasin Tuur) and the Mongolian Empire (Karakorum) near the recent town of Kharkhorin, Central Mongolia. A holistic approach involving the use of high spatial resolution geomorphological mapping, sedimentological and geochemical analysis, palynology, and geochronology shows several phases of landscape activity and stability in the region. This includes phases of fluvial erosion, aeolian sedimentation, and soil formation. By using luminescence and radiocarbon dating, phases of landscape change, indicated by soil formation, occurred mainly at around 6.5-6 ka. Pollen data and a weakly humic horizon at around 1.0 ka probably indicate enhanced moisture supply in the region and a reduction of human activity between the time of the reigns of the Uighurs (8th-9th century AD) and the Mongols (1220-1388 AD). Since 3 ka, especially within the last two millennia of Historical Time (300 B.C.-present), a more intensified human occupation in the Upper Orkhon Valley occurred in this region. This included a more densely grazing of cattle to supply the growing population demands of the Uighurs and Mongols. This overgrazing caused an increase in erosion and the formation and deepening of fluvial gullies. together with soil deflation and subsequent deposition of aeolian sediments. Human activity, in addition to climate, has been dominant in driving landscape evolution of this region since the late Holocene. (C) 2011 Elsevier B.V. All rights reserved