Project 581 - Evolution of Asian River Systems
Most of the large rivers in Asia such as the Yangtze River, Yellow River, Indus River, Ganges/Bramaputra Rivers, Mekong and Red Rivers originate from the Himalayan-Tibet and drain large continental areas prevailed by monsoon precipitation. Therefore, the origin and nature of these large Asian rivers are highly sensitive to plateau uplift and monsoon evolution. These large drainage basins are also densely populated, and socio-economical developments in East and South Asian countries significantly depend on control and utilization of these rivers. A better understanding of the evolution of these river systems, both in recent and geological past, is beneficial not only to our knowledge about Earth dynamics, but also to social sustainability. Big river systems are an integral and essential part of Earth dynamics. They play significant roles in geomorphology at all scales, tectonics (erosion induced uplift and isostatic rebalancing of the crust), and filling of sedimentary basins. Most prominently, they act as the transfer of continental mass (solids and chemical compounds in solution) to the ocean, thus playing major roles in global geochemical cycles. On geological time scale, rivers’ evolution involves tectonics (global and regional) and climate. Therefore, study of large river systems may hold the key to understanding of the mechanism of tectonic-climate linkage. Asia has experienced dramatic changes in both tectonics and climate during the Cenozoic. Uplift of the Tibetan Plateau is the most single event that largely shaped the landscape and drainage networks of Asia, and is attributed to have induced Asian monsoon regime and other global climatic events. However, the nature and mechanism of the linkage between each of the tectonic and monsoon evolution events still remains one of the major problems in earth science. For example, uplift of the Tibetan Plateau and surrounding ranges enhanced erosion and weathering, a process that has been hypothesized to count for the partial drawdown of CO2 and global cooling during the Cenozoic. On the other hand, the sedimentary yields of Asian rivers are by far the largest in the world owing to high erosion rate and monsoon precipitation, a process that enhances the carbon burial and causes changes in global carbon reservoir. Therefore, a full understanding of the mechanism of tectonic-climate linkage during the Cenozoic requires a comprehensive study of Asian tectonics, climate and evolution of river systems. The project plans to conduct a group effort to:
- use sedimentary archives, both onshore and offshore, to trace the evolutionary history of Asian big river systems,
- correlate continental and marine tectonic and climatic records, in particular, those about the uplift of Tibetan Plateau and monsoonal evolution, and examine their interrelations,
- study the sediment budget of Asian large rivers, and assess the contribution of erosion, chemical weathering and sedimentation in Asia to global carbon cycles,
- and carry out numerical modeling to study the linking mechanism among tectonics, chemical weathering, and monsoon evolution during the Cenozoic.
Through these studies, it is planned to create a new model on the tectonics and climate linkage in East Asia and their impact on global climate, and elaborate a strategy to test the model by utilizing international sediment sampling programmes such as IODP, ICDP, and IMAGES.