HR: 0800h
AN: PP41A-0586    [Abstracts]
TI: Neogene Carbonate Platforms as Recorders of the Onset and Strengthening of the East Asian Monsoon
AU: * Dorobek, S L
EM: dorobek@geo.tamu.edu
AF: Texas A and M University, Dept. of Geology & Geophysics, College Station, TX 77843 United States
AB: Miocene to Recent carbonate platforms from southern parts of the South China Sea and Indonesian back-arc region have variable internal growth patterns that likely reflect the onset and strengthening of the East Asian Monsoon, an annual seasonal cycle where precipitation, and more importantly for this study, wind directions change dramatically. Extensive high-quality seismic-reflection data were examined across the study area and showed that isolated carbonate platforms commonly have asymmetrical facies distributions and internal stratal patterns that reflect prevailing paleowind directions during growth. Early to middle Miocene platforms throughout the study area show consistent windward-leeward asymmetry, which suggests that prevailing winds were fairly constant over long time scales. Starting at about 11 Ma, however, growth patterns became much more variable in many platforms, especially those from the East Natuna Basin and offshore Vietnam. These complex growth patterns continue until the present day. In the Indonesian backarc region, middle to late Miocene isolated platforms show strongly asymmetrical but consistent growth patterns that also reflect strengthening of the East Asian Monsoon at this time because prevailing winds during the winter monsoon are out of the west and stronger than the weaker, easterly winds of the summer monsoon. Thus, Neogene isolated carbonate platforms of the southern South China Sea and Indonesian backarc region may be some of the best recorders of the evolution of the East Asian Monsoon.
DE: 9320 Asia
DE: 9604 Cenozoic
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 3025 Marine seismics (0935)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting