Is evolution of calcareous phytoplankton related to shallow marine carbonate system dynamics?

点击翻译按钮获取中文摘要

IOPD Expedition 359, Sea Level, Currents, and Monsoon Evolution in the Indian Ocean will be investigating the Maldives Ridge which stretches southward through the Indian Ocean as a double chain of coral atolls. These atolls lie along a volcanic ridge which formed over a mantle hotspot as the Indian plate moved northwards. As the ridge cooled it subsided to be replaced at the surface by the string of atolls and between them deeper troughs.Within these troughs vast thicknesses of carbonate sediments derived from the ridge have built up intermixed with open ocean sediments. These sediments provide a unique opportunity to examine the relationships between open ocean planktonic carbonates and shallow marine carbonates - which normally are difficult to compare. This project seeks to exploit this opportunity to see whether there are any consistent correlations between changes in the pelagic carbonate producing coccolithophores and the shallow marine carbonate system. If such correlations do occur it will provide strong evidence that abiotic factors such as temperature and sea water chemistry have strong influences on large scale evolution of these systems. Conversely if no such linkages can be observed it will cal into question the degree to which changes in for instance coccolithophore abundance or calcification are interpreted as being caused by abiotic factors.The great thicknesses of the successions also mean that intervals of abrupt change in plankton assemblages can be studied at higher resolution than is normally possible. This will provide the opportunity to test if such changes are caused by environmental events. The project will specifically focus on size variation in the dominant group of coccolithophores the reiticulofenestrids. This group shows a long term size reduction but this is formed of series of abrupt size reduction events separated by extended intervals of size increase. This will be the first time the set of size reduction events from the middle Miocene to the recent have been studied systematically in one place as well as testing to see if they correlate with change in environmental proxies or changes in the shallow marine carbonate system.