HR: 1340h
AN: PP23A-1070    [Abstracts]
TI: A Multi-Proxy Approach to Reconstruct the Hydrological Changes and Holocene Climate Development of Nam Co, Central Tibet
AU: Gleixner, G
EM: ggleix@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, Hans Knöll Str. 10, Jena, 07745, Germany
AU: * Muegler, I
EM: imuegler@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, Hans Knöll Str. 10, Jena, 07745, Germany
AU: Maeusbacher, R
EM: crm@uni-jena.de
AF: Friedrich Schiller University, Loebdergraben 2, Jena, 07743, Germany
AU: Daut, G
EM: gerhard.daut@uni-jena.de
AF: Friedrich Schiller University, Loebdergraben 2, Jena, 07743, Germany
AU: Schwalb, A
EM: antje.schwalb@tu-bs.de
AF: Technische Universitaet, Pockelsstrasse 3, Braunschweig, 38106, Germany
AU: Schuett, B
EM: schuett@geog.fu-berlin.de
AF: Freie Universitaet, Maltheserstr. 74-100, Berlin, 12249, Germany
AU: Yao, T
EM: tdyao@itpcas.ac.cn
AF: Institute for Tibetan Plateau Research, P.O. Box 2871, Beijing, 100085, China
AU: Xu, B
EM: baiqing@itpcas.ac.cn
AF: Institute for Tibetan Plateau Research, P.O. Box 2871, Beijing, 100085, China
AU: Zhu, L
EM: zhulp@igsnrr.ac.cn
AF: Institute for Tibetan Plateau Research, P.O. Box 2871, Beijing, 100085, China
AU: Yi, C
EM: clyi@itpcas.ac.cn
AF: Institute for Tibetan Plateau Research, P.O. Box 2871, Beijing, 100085, China
AB: Holocene lake level fluctuations of Nam Co, Central Tibet, as an expression of monsoon strength variations are recorded in a 2.6 m long sediment core dating back at least 7.2 cal. ka BP. By means of a multi proxy approach integrating sedimentological, geochemical and mineralogical analyses with special focus on compound-specific hydrogen isotope ratios of sedimentary n-alkanes Nam Co Holocene climate evolution is divided into at least five depositional units. Additionally, geomorphological features in the catchment such as beach ridges and lake terraces point to pre-LGM high stands. Sands and sandy silts at the base of the core are interpreted as beach sediments. This suggests that lake level was about 35 m lower than today before approx. 7300 cal years BP. Sediments in unit I (until ~5.8 cal ka BP) are assumed to be deposited at highest lake levels within the sediment sequence. Isotopically depleted terrestrial and aquatic n-alkanes imply high precipitation and melt water input suggesting a positive water balance. Continuous increasing aquatic productivity points to favorable environmental conditions. Unit II (~5.8 cal ka BP to ~4.2 cal ka BP) being characterized as transition zone reflects stable hydrological conditions with the beginning of lake level decrease. Within this unit two remarkably drier periods with increased evaporation occurred around 5.75 cal ka BP and around 4.75 cal ka BP leading to significant enrichment of lake water \( δD \) values. Significant lower lake levels as consequence of a dryer climate with less monsoonal precipitation, higher evaporation rates and increased moisture recycling in the catchment are reflected in the sediments in Unit III (~4.2 cal ka BP to ~1.75 cal ka BP). Most pronounced dry periods are recorded around 3.75 cal ka BP and 2 cal ka BP again leading to deuterium enrichment of aquatic derived n-alkanes. A break of the proceeding lake shrinkage and salinisation occurs in the first section of Unit IV (~1.75 cal ka BP to ~800 cal years BP to ~500 cal years BP) where an ongoing increase in precipitation and runoff leads to at least a stable but still low lake level. The most recent Unit V (since 500 cal years BP) is characterized by an intensive progressing lake shrinking due to intensive evaporation but with intermittent monsoonal precipitation events being reflected by the variations in the geochemical parameters referring to alternating humid and arid periods at Nam Co. Although correlation with other lake records from the Tibetan Plateau suggests an overall agreement with the broader picture of Holocene environmental evolution, inconsistencies still exist concerning reliable chronologies. Thus, further research is needed to improve the spatiotemporal interpretation of hydrological variations in association with alternating monsoonal circulation across the Asian continent.
DE: 0429 Climate dynamics (1620)
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1105 Quaternary geochronology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting