Interplay between Lake and Catchment Processes in Kuhai Lake Basin, NE Tibetan Plateau, China, during Late Holocene

by Dada YAN

Institution: Freie Universitt Berlin
Year: 2017
Posted: 02/01/2018
Record ID: 2154183
Full text PDF: http://edocs.fu-berlin.de/diss/receive/FUDISS_thesis_000000104638


The Tibetan Plateau (TP), the largest and highest plateau in the world and important water resource region for billions of people on the Asian continent, is considered a unique area in Central Asia for deciphering the relationship between landscape evolution and climate impact. Lake basins and their catchments are therefore valuable research objects for studying the process-response behavior of individual systems as they react very sensitive to climatic and non-climatic factors that influence sediment and water flux from the sources to the sinks. Commonly, these processes are archived in sediments of lakes as long as they persist and are not subject to erosion/deflation. Hence, many researchers concentrated on lake research on the TP to elucidate the evolution of lakes in response to climate impact, for example. Especially the interplay between the Asian Monsoon system and the mid-latitude Westerlies are in the focus of such studies. The overwhelming majority of research results based on various proxy data rely on sediment records from lakes, derived from a single sediment core, preferably retrieved from the deepest and central part of lake basins. The results imply that the proxy data, extracted from the respective sediment parameters, are spatially and temporally valid for the entire research region and beyond. In most cases, catchment dynamics and their interaction with the lake were not or less considered for the overall interpretation of climate- and/or non-climate-induced processes that influenced the lake hydrology and its evolution through time. The Kuhai Lake Basin, located on the north-eastern TP, was selected for this study in order to combine investigations in the lakes catchment with those on the lake itself. This strategy was considered a necessary requirement for a better understanding of interrelated processes responsible for the evolution of the lake. Especially their response to climate impact by the East Asian Summer monsoon (EASM) and the Westerlies were in the focus of this study. Geomorphological studies in the catchment of the lake were conducted with focus on the drainage systems and their sediments, combined with morphological landforms formed by aeolian processes. Thirty sediment sections were investigated by means of sediment composition (grain size) and fossil remains (ostracod), where possible. In addition, selected sediment sequences in several sections were dated by radiocarbon-AMS or OSL techniques. Sediments from the lake were used for detailed high-resolution analysis. They comprised 57 lake surface samples covering the entire lake basin and four sediment cores with individual lengths of up to 2.75 m from different locations in the lake. The chronology of all sediment cores was achieved by radiocarbon-AMS dating on different fractions from bulk samples and/or plant remains. 210Pb/137Cs dating was used for age control of the upper 25 cm sediment from one core. Records from the lake cover the last 4000 years of sedimentation history.High-resolution analyses (1 or 2 cm