Carbonate factory turnovers influenced by the monsoon (Xisha Islands, South China Sea)

Carbonate factory turnovers are the integrated result of climatic, oceanographic and biological controls. Sedimentological, geochemical and palaeontological data from core XK-1 drilled in the Xisha Islands, South China Sea, reveal that photozoan to heterozoan carbonate factory turnovers during the Early and Middle Miocene in isolated carbonate platforms were mainly caused by changes in the upwelling regime. A heterozoan open bank association thrived in tropical shallow water under conditions of nutrient excess, indicated by high ln(Cu/Ti) and ln(Ba/Ti), and by the increased abundances of rhodoliths and some foraminifer genera. During the Early and Middle Miocene, episodes characterized by a heterozoan carbonate production correlate with times of East Asian Summer Monsoon strengthening, especially from 21.2 to 17.3 Ma and from 15.6 to 11.6 Ma. This study thus provides new insights into the variability of shallow water carbonate deposition in monsoon-influenced areas and also shows that carbonate factory turnovers can contribute to a better understanding of the monsoon's evolution.