| The focus of the study is to determine how the uplift of the Tibetan Plateau affected the climate of eastern Asia and how continental climatic fluctuations restructured these lacustrine systems in response to the earth's orbital changes.; Main results are: (1) Chemical element data from the northern basin of Lake Baikal show a sharp change in the postglacial limnology due to climate change, cessation of meltwater input and the rapid resumption of biogenic productivity in the surface waters, principally by diatoms. (2) The stratigraphic records of total organic carbon (TOC), nitrogen (%N), arboreal pollen (AP) and stable carbon isotopes in Lake Baikal and Lake Qinghai exhibit remarkable agreement during the last 11,000 years. Fluctuations in the carbon cycle of both lakes reflect the impact of the last glacial-Holocene transition on both lake watersheds. Both regions experienced a similar pattern of climatic changes. (3) Evaporite accumulation in Qaidam Basin during the Brunhes epoch was due to repeated evaporation/precipitation imbalance which resulted in {dollar}sp{lcub}18{rcub}{dollar}O and {dollar}sp{lcub}13{rcub}{dollar}C enrichment in the carbonate sediments. (4) In the Lake Dianchi region, heavy rainfall from monsoon maxima results in higher organic carbon and magnetic mineral contents in the sediment in response to rainforest development. (5) Climatic change frequencies in both Qaidam and Dianchi due to lake level changes and the evolution of terrestrial vegetation systems during the Brunhes are similar to the earth's orbital components of precession and obliquity (tilt). The spectral character of the paleoclimatic records of Qaidam and Dianchi are significantly changed by the extent of the Tibetan Plateau uplift. Obliquity and precession signals increase north of the plateau (Qaidam) and decrease south of the plateau (Dianchi) because of blockage of atmospheric circulation processes in the mid-latitude parts of the northern hemisphere. (Abstract shortened by UMI.)... |
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