RELATION OF EUSTASY TO CLIMATE CHANGE IN SOUTHEAST ASIA AND AUSTRALIA

The shallow epeiric seas and gulfs of Southeast Asia are located in a strategic location that affects climate and ocean surface circulation during changes in sea level. Areas less than 200 m deep include the Gulf of Thailand, the southern South China Sea, the Java Sea, the Arafura Sea, and the Gulf of Carpentaria. Results of drilling in the Mahakam Delta, Kalimantan, Indonesia (Caratini and Tissot, 1988), indicate that the climate on the equator changed from drier or seasonal conditions supporting grasses at the last glacial maximum to the modern perhumid (everwet) condition that supports a rainforest. Results from high-resolution seismic reflection data gathered in the 70-m-deep Gulf of Carpentaria indicate that the floor of the gulf was exposed about 14 times based on basin-wide reflections and associated paleochannels. Cores contain a paleosol probably formed at the end of the Pleistocene. The frequent fluctuations in sea level in the epeiric seas of the Southeast Asia region may have had a significant control on atmospheric humidity and temperature as a result of increased sea surface during highstands (reduced land surface) and greatly diminished sea surface (greater land surface) during lowstands. The effects of eustasy on equatorial ocean circulation in the region require further investigation, but these effects were likely significant.