Advances in Earth Science
• Articles •
1, Zhou Zuyi
Zheng Hongbo,Wang Pinxian,Liu Zhifei,Yang Shouye,Wang Jialin,Li Qianyu,Zhou Zuyi. Carving the History of East Asia′s East-Tilting Topography and East Asian Monsoon—An Introduction to IODP Proposal 683[J]. Advances in Earth Science, 2008, 23(11): 1150-1160.
Ocean drilling in the Bengal Fan has revealed the uplift history of the Himalayas and Indian monsoon, but there is no analogous deep-water fan in the Western Pacific marginal seas that can be drilled and used to constrain the Tibet uplift history from its eastern side. The Yangtze river, originating from northeastern Tibet and draining a large area prevailed by monsoon precipitation, is highly sensitive to plateau uplift and monsoon evolution. A systematical study of the Yangtze river deposits will test various hypotheses concerning plateau uplift and its link with monsoon evolution. Along the modern Yangtze river, the upper reach is decoupled from the lower reach by the Three Gorges. About 30% of the total sediment load from the Yangtze river is laid in the Jianghan Basin immediately out from the Gorges, ~40% is deposited in the lower reach and delta, and only ~30% is transported to the East China Sea. Therefore, a combination of ocean and continental drilling along the Yangtze River will recover records useful for carving the history of uplift and monsoon. A close timing of tectonic and climatic events mainly at four time intervals has been proposed as evidence for a link between Tibet uplift and the Asian monsoon initiation: the late Pliocene (2~3 Ma), the late Miocene (~8 Ma), the early-middle Miocene (~15 Ma) and the latest Oligocene (~25 Ma). On the basis of the Three Gorges incision or delta development data, however, the history of the Yangtze River can be traced back only to the late Pliocene or early Pleistocene, and the East China Sea came into existence only in the latest Miocene. A younger Yangtze river is in a sharp contrast to the early uplift of Tibet. In the Paleogene, a broad belt of aridity stretched across China from west to east, and numerous lake basins developed in rift grabens, prohibiting any east-flowing large rivers. Large rivers like the Yangtze river could have developed only since Neogene with the advent of an east-tilting topography and monsoon in East Asia. The proposed joint IODP/ICDP project will provide sediment records from marine and terrestrial basins to help clarify the most puzzling issues in East Asian environmental evolution and to test the hypothetical link between Tibetan uplift and monsoon climate from the eastern side of the plateau.