SE Asian carbonates: tools for evaluating environmental and climatic change in equatorial tropics over the last 50 million years
Moyra E. J. Wilson, 2011. "SE Asian carbonates: tools for evaluating environmental and climatic change in equatorial tropics over the last 50 million years", 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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This study reviews how shallow water carbonates are revealing environmental and climatic changes on all scales through the last 50 million years in SE Asia. Marine biodiversity reaches a global maximum in the region, yet the environmental conditions are at odds with the traditional view of ‘blue-water’ reefal development. The region is characterized by complex tectonics, major volcanism, high terrestrial runoff, nutrient influx, everwet and monsoonal climates, low salinities, major currents and ENSO (El Niño Southern Oscillation) fluctuations. Terrestrial runoff, nutrient upwelling, tectonics, volcanism and recent human activities are major influences on the modern development of carbonate systems. Coral sclerochronology is revealing how these factors vary locally over annual and decadal scales. The strong impact of vertical tectonic movements and the interplay with eustasy is evaluated from Quaternary and Pleistocene coral reef terraces. Isotopic data from terrace deposits indicates that interglacials may have been up to 3–6 °C warmer than glacials, consistent with the region's record from terrestrial and deep marine deposits. Study of outcrop and subsurface carbonate deposits reveals the impact of tectonics, siliciclastic, nutrient influx, eustasy and oceanography on individual systems over millennial timescales. Major changes in oceanography, plate tectonics, climate change and perhaps fluctuating CO2 levels impacted Cenozoic regional carbonate development. Results of studies from terrestrial and deep marine realms are comparable with those from the carbonates, but have yielded higher resolution records of changing currents, precipitation and the monsoons. There is considerable scope for further research, however, SE Asian carbonates are powerful tools in evaluating past environmental change in the equatorial tropics.
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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.