PP11D-04
Late Quaternary Lake‐System Dynamics on the northern Tibetan Plateau
Monday, 14 December 2015: 08:45
2012 (Moscone West)
Bernhard Diekmann1, Arne Christian Ramisch1,2, Gregori Lockot3, Torsten Haberzettl4, Kai Hartmann5, Frank Lehmkuhl6, Georg Stauch6, Bernd Wuennemann7 and Yongzhan Zhang7, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany, (2)Technische Universität München, Freising-Weihenstephan, Germany, (3)Free University Berlin, Institute of Geographical Science, Berlin, Germany, (4)Friedrich Schiller University of Jena, Physical Geography, Jena, Germany, (5)Free University of Berlin, Berlin, Germany, (6)RWTH Aachen University, Aachen, Germany, (7)Nanjing University, Nanjing, China
Abstract:
Lake systems on the Tibetan Plateau exhibit complex responses to late Quaternary climate variations, driven by monsoon dynamics and the influence of the westerlies regime. A limnogeological case study from Lake Heihai, situated at 4440 m a.s.l. on the northern Tibetan Plateau, gives evidence for marked changes in the depositional environment related to climatic and orographic effects. The 10 km long, 4 km wide, and 22 m deep lake is situated in a basin north of the Kunlun Mountain Range. Sub-bottom profiling revealed the presence of subaquatic terraces and ancient fan systems from a former low lake stand, draped by younger sediments. Sediment cores above basal sands comprise lacustrine sediments of late glacial to Holocene age. Proxy records document marked changes in allogenic sediment provenance and endogenic carbonate precipitation during the last 12 ka. The interpretation of these changes points to dominant detrital sediment and water supply from proximal alluvial fans during times, when precipiation was not blocked by the Kunlun Mountains. After a prolonged dry and cold phase during the Late Glacial, the situation of enhanced precipitation-generated sediment supply ocurred between 10.7 cal. ka BP and 7.9 cal. ka BP and decreased afterwards. The moist stage is also documented by a prominent lake terrace about 6 m above modern level that gives evidence of a higher lake level. The terrace structure includes fossil lake sediments, which were invaded by ground ice after lake-level fall and today reveal marked permafrost structures.The Holocene trend in lake hydrology is in phase with known variations in atmospheric circulation systems over monsoonal Asia.
