PROVENANCE EVOLUTION OF THE PALEO-HANJIAN RIVER IN THE NORTH SOUTH CHINA SEA

The Pearl and Hanjiang rivers are the two important terrigenous sediment sources for the Hanjiang-Lufeng area in the northern part of the South China Sea (SCS) since Paleogene. In Eocene, the partition coefficients of the rare-earth elements of the sediments varied from region to region,indicating that there is no large river dominating the region for sediments supply.The nearby uplifting areas were the major source areas. In the Oligocene, Hanjiang River and Pearl River just appeared,and the Hanjiang River was relatively larger than the Pearl River then and could provide most of the sediments to the east and middle part,whereas the Pearl River could only affect the northwest and west part of the research area.Up to early Miocene, the sediment from the Hanjiang River source area reached the southwest part, and even the west part of the research area, reflecting the expansion of the Hanjiang River source area.The Hanjiang River started retreating in the middle Miocene.As the result, the sediments from both rivers deposited together in the southwest part of the research area and the Lf14 region started receiving sediments from the Pearl River at this time. Because of the sea level rise,sediments from the two rivers were decreased in the research area, and brought about the deposition of the mixed mud and carbonate deposits in an epicontinental sea environment in late Miocene. Besides the terrigenous sediments from the two rivers, there were some basic volcanic materials coming from the Dongsa Uplift during the period from Oligocene to early Miocene that led to the positive anomaly of element Eu in the Lf7 and Lf14 regions in the south.