Neogene climate history of the Makassar Straits, Indonesia
Robert J. Morley, Harsanti P. Morley, 2011. "Neogene climate history of the Makassar Straits, Indonesia", The SE Asian Gateway: History and Tectonics of the Australia-Asia Collision, R. Hall, M. A. Cottam, M. E. J. Wilson
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The Neogene climate history of the Makassar Straits has been assessed by combining palynological studies of two Late Quaternary cores from the ocean floor with analyses of petroleum exploration wells from the Makassar Straits, Indonesia, penetrating the Early Pleistocene to Middle Miocene.
The two Late Quaternary cores span 30 ka, located offshore the Mahakam Delta, east Kalimantan, and 95 ka, from offshore south Sulawesi. The first provides a record of the vegetation and climate history of the Mahakam catchment, and indicates rain forests through the last 30 ka, but with a cooler last glacial maximum, whereas the second provides a record of vegetation of the Java Sea region and south Sulawesi, and indicates extensive grasslands, suggesting a distinctly seasonal climate, during the last glacial maximum.
Based on a climate model constructed from the cores which link sea level change with changes of temperature and seasonality, the history of vegetation and climate for the Makassar Straits is then extrapolated back to the Middle Miocene using the record obtained from the two exploration wells. Results show that the equatorial climate has been everwet since the Middle Miocene, but at subequatorial latitudes seasonal climates became established from the Late Pliocene onward.
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Collision between Australia and SE Asia began in the Early Miocene and reduced the former wide ocean between them to a complex passage which connects the Pacific and Indian Oceans. Today, the Indonesian Throughflow passes through this gateway and plays an important role in global thermohaline flow. The surrounding region contains the maximum global diversity for many marine and terrestrial organisms. Reconstruction of this geologically complex region is essential for understanding its role in oceanic and atmospheric circulation, climate impacts, and the origin of its biodiversity.
The papers in this volume discuss the Palaeozoic to Cenozoic geological background to Australia and SE Asia collision. They provide the background for accounts of the modern Indonesian Throughflow and oceanographic changes since the Neogene, and consider aspects of the region’s climate history.