HOLOCENE DELTA EVOLUTION IN ASIA: IGCP-475 DELTAMAP PROJECT

The delta is an important and typical coastal feature. In particular, large rivers form huge deltas in South, Southeast, and East Asia. More than 50% of the world's population lives in Asia, and most of Asia's population lives in deltaic areas. Moreover, more than 80% of the world's total area of rice paddies is in Asia. Deltaic lowlands in Asia are also important to the study of sedimentology and global sediment flux. Rivers in Asia and Oceania contribute about 70% to 80% of the world's sediment flux from the land to the ocean. Deposits of these huge sediment discharges have formed mega-deltas during the last 6-7 kys. Why are so many large deltas distributed along the Asian coast? One is the presence of large rivers with a high sediment yield, which have their sources from the Himalayas and the Tibetan Plateau and with high precipitation due to the monsoonal climate. The other is the stable or slightly falling sea level over the last 6-7 kys. Most of the Asian region recorded a middle Holocene sea-level highstand 2-4 m above the present sea level about 6-7 ka by hydro-isostasy. The long-stable sea level has allowed more than 200 km of shoreline migration since this period and the formation of deltas with a wide delta plain. A new IGCP project, IGCP-475 "Deltas in the Monsoon Asia-Pacific Region (DeltaMAP): Late Quaternary Development and Recent Changes Due to Natural and Human Influences" has started as a 5-year project from 2003-2007. In terms of sedimentary dynamics, active margin processes, and human-related issues, the monsoon Asia-Pacific encompasses probably the world's most exciting region for sedimentary research. This area also includes a breadth of climatic, tectonic, and anthropogenically-altered environments. The project seeks to understand these diverse settings within the unifying theme of monsoon-driven sedimentary systems. Primary goals for the next 5 years will be to (1) develop an adaptive and comprehensive conceptual model for monsoon-driven river-delta systems and (2) enhance regional and international collaboration on delta research. The first annual meeting of IGCP-475 will be held in Thailand from January 16-21, 2004, jointly organized with the 5th International Conference on Asian Marine Geology (held in Bangkok, 13-18 January, 2004).