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Abrupt Deglaciation On The Northeastern Tibetan Plateau: Evidence From The Lacustrine Sediment Cores At Lake Qinghai

Xiuju Liu
Large Lakes Observatory & Department of Earth Sciences, University of Minnesota Twin Cities, Minneapolis, MN 55455, USA

The Tibetan Plateau has long been considered a major control on Asian monsoon, which provides the rainfall that sustai ns more than half of the world’s human population and the ecosystem over Asia. It is crucial to understand the monsoonal dynamics and to predict rai nfall patterns for long term adaptation planning . There is a long standing controversy about Tibet’s thermal role by heating the overlyi ng atmosphere versus its mechanical role by serving as a barrier to air flow in shaping Asian climate. To better understand Tibet’s effect, we exami ned sediments from core QH07, taken in the Lake Qinghai at the northeastern margin of the Tibetan Plateau. The lithological, sedimentological, and geochemical characteristics of the QH07 sediments are i nternally consistent. The indicators of summer monsoon moisture in QH07 provide a climate history that is subtly different from that of the lowland speleothem records from southern and eastern China. Comparati vely, the Lake Qinghai data suggest: a relati vely stable, dry glacial interval; unexpectedly small variations during the Bølling–Allerød intervals and the Younger Dryas; an extremely abrupt late Pleistocene/Holocene transition; and a relatively unstable, wet early Holocene. These characters taken together suggest that a climate threshold exists for penetration of the Asian monsoon into the Tibetan Plateau, and the threshold was crossed at the beginni ng of the Holocene. Conceptually, the threshold may be related to orographic i nsulation and topographic deflection controlling the Asian monsoon dynamics. Thus, our results show evidence of the mechanical forci ng for the Tibetan Plateau rather than plateau heating.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013