Louisiana State University
“Drainage Capture and Topographic Evolution of Cenozoic East Asia”
It has long been recognized that the geometry of river systems in Southeast Asia are very unusual with several large systems lying close together in a way suggestive of large-scale crustal shortening or the disruption of earlier large river systems that existed before the start of India-Asia collision. Timing of the drainage capture is important for constraining the tilting of Asia to the east during the Cenozoic and the start of major uplift of the Tibetan plateau. The Red River in particular has been highlighted as the potential original lower reaches of a large system. Data from the Irrawaddy and Yangtze support concept that the head of this earlier drainage system was diverted in adjacent basins sometime around the start of the Miocene. U-Pb dating of detrital zircon grains now supports earlier bulk sediment chemistry in arguing for a more extensive drainage system that is now being reorganized. Uplift of the southeastern edge of the Tibetan plateau appears to be much earlier than that seen along the northern edge in western China, as well is in the headwaters of the Yellow River. Drainage capture needs to be appropriately corrected for using sedimentation rates in delta systems as a proxy for continental erosion, potentially controlled by the Asian monsoon.