Understanding sedimentation in the Song Hong-Yinggehai Basin, South China Sea

Abstract

[1] The Cenozoic Song Hong-Yinggehai Basin in the South China Sea contains a large volume of sediment that has been used in previous studies, together with regional geomorphology, to argue for the existence of a large palaeodrainage system that connected eastern Tibet with the South China Sea. To test this and to understand the significance of sediment volumes deposited in the Song Hong-Yinggehai Basin, this study compared erosion histories of source regions with sediment volumes deposited during the two main stages in basin evolution spanning active rifting and subsidence (30-15.5 Ma) and postrift sedimentation (15.5 Ma to present). The study of basin provenance by detrital zircon U-Pb dating revealed Hainan was an important and continuous source of sediment, and a bedrock thermochronological study quantified its overall contribution to basin sedimentation. Comparison between the accumulated mass of basin sediment and volumes of eroded bedrock, calculated from apatite thermochronometry across the modern Red River drainage in northern Vietnam as well as Hainan Island, accounted for the bulk of sediment deposited since 30 Ma. Consequently, if an expanded paleodrainage ever existed it must have predated the Oligocene.

Zircon U-Pb geochronology and heavy mineral composition constraints on the provenance of the middle Miocene deep-water reservoir sedimentary rocks in the Yinggehai-Song Hong Basin, South China Sea

“…10B). Previous studies show that the provenance from Hainan has main age ranging from 110e90 Ma to 280e220 Ma on the eastern margin of the Y-SH Basin (Yan et al, 2011;Wang et al, 2015a). The sediments from modern rivers in the western Hainan also give the same results with age peaks at ca.…”

“…The previous provenance studies have illustrated that the Cenozoic sediments of the Y-SH Basin were from three major source terrains, the southern Yangtze Block (Red River), Indochina Block (central Vietnam) and Hainan Uplift (Gong et al, 1997;Brookfield, 1998;Clift and Sun, 2006;Xie, 2009;Yan et al, 2011;Wang et al, 2014bWang et al, , 2015aCao et al, 2015;Jiang et al, 2015) (Fig. 9).…”

“…During 16e5.5 Ma, depocenters gradually migrated back to the northwest, and paused in the northwestern basin ). Slowdown of dextral movement and high rates of sediment supply led to overflow of the Y-SH Basin to the east into the Qiongdongnan Basin (Yan et al, 2011).…”

“…The Y-SH Basin contains up to 17 km of Paleogene to Quaternary sedimentary rocks (Gong et al, 1997;Yan et al, 2011). The clastic sediments that filled the central Yinggehai depression during the Neogene to Quaternary include lacustrine, coastal plain and neritic (before 30 Ma), littoral to neritic (30e10 Ma) and littoral to bathyal environments (after 10 Ma) (Fig.…”

“…Although there have been detrital zircon studies of the Cenozoic sedimentary rocks of the Y-SH Basin (Yan et al, 2011;Wang et al, 2014b;Cao et al, 2015;Jiang et al, 2015;Wang et al, 2015aWang et al, , 2016b, no attempt has been made to apply the zircon geochronology and heavy minerals to the middle Miocene strata systematically. This study, we set out to document U-Pb ages of detrital zircons and heavy mineral assemblages from marine core samples to constrain the possible sediment provenance and transport pathway of the middle Miocene Meishan Formation and discuss the contribution of the source terrains.…”