Depositional characteristics of the northern South China Sea in response to the evolution of the Pearl River

Abstract

Geochemical data from South China Sea sedimentary rocks show the effects of both source composition and depositional environments. This enables us to link tectonic trends with erosion in the Pearl River region since c. 32 Ma. In particular, a shift in the geochemistry appears to signal a response to a well-recorded regional tectonic event at c. 23-25 Ma, probably corresponding to a jump in the seafloor spreading axis from the west to the SW within the South China Sea. This may correlate with the uplift of the West Yunnan Plateau and possibly also the eastern Tibetan Plateau. Clay mineralogy, sand-mud ratio, and major and rare earth element concentrations, also varied in response to the environment in the drainage areas of the palaeo-Pearl River. By comparing data from the modern sources and the sedimentary record from the northern South China Sea, especially the erosion-transportation-deposition patterns, three groups of index minerals (Ati, GZi, ZTR), as well as rare earth elements can be recognized. These are used to characterize the Pearl River from the east to the west, representing three different parent rock sources. The evolution of the palaeo-Pearl River can be tracked by variations of heavy minerals and key elements that are indicative of provenance.

Provenance of Upper Miocene sediments in the Yinggehai and Qiongdongnan basins, northwestern South China Sea: Evidence from REE, heavy minerals and zircon U–Pb ages

“…3; Tu et al, 1991;Ho et al, 2000). 2) The Miocene sediments from the PRMB have the relatively high CaO content and low Al 2 O 3 content, which may indicate a provenance from the Paleozoic carbonate rocks in South China (Shao et al, 2013). Northern Hainan Island and South China thus seem less likely as the source areas for the Shenhu Uplift.…”

Detrital zircon provenance of the Paleogene syn‐rift sediments in the northern South China Sea

“…[] favored a sediment source from the southward drifting Palawan Continental Terrane, but their interpretation of geochemical signatures in terms of potential source areas were largely derived from modern sediments, which may not fully represent those of the Paleogene source‐to‐sink systems. In contrast to these interpretations of a southern margin source for the basin sediments, most provenance studies emphasize a northern provenance from South China based on sedimentary and conventional geochemical evidence [e.g., Clift et al ., ; Shao et al ., ; Lan et al ., ]. This viewpoint is also supported by apatite fission track analyses from southeastern South China that revealed rapid cooling episodes during the Eocene‐Oligocene [ Yi et al ., ].…”

Using Detrital Zircon Geochronology to Constrain Paleogene Provenance and Its Relationship to Rifting in the Zhu 1 Depression, Pearl River Mouth Basin, South China Sea

“…The studies cover the major rivers that cross the mainland of China, like the Red River (Clift et al, ), the Pearl River (Shao et al, ), and the Yangtze River (Zhang et al, ; Zheng et al, ), and while they emphasize drainage expansions and reorganizations, on the northern margin of the SCS, as a primary influence on onshore and offshore sediment, the timing documented by these studies do not match the syn‐rift sequences analyzed in this paper. For the Pearl River system, several important changes in geochemical composition have been recorded in sediments from boreholes in the PRMB and ODP Site 1,148 (Shao et al, ). Among the events, the most pronounced occurred at ∼23.8 Ma and is interpreted to have been caused by the catchment expansion to western plateau of Pearl River (Shao et al, ).…”

“…Indosinian gneissic granites formed in the early Triassic, with the zircon U‐Pb ages of 250–242 Ma, while massive granites range from 248 to 202 Ma (Wang et al, ). Because sediment in the Zhu 1 depression was dominately dip‐fed (Jiang et al, ; Liu et al, ; Shao et al, ; Shu et al, ), grains with Paleozoic and Triassic ages, shown in Figure , are likely to have been sourced from the rocks in the SCB. The number of zircons that fall into this Kwangsian interval varies substantially from the Wenchang (6 of 137, 4%; 1 of 83 in lower Wenchang to 5 of 54 in upper Wenchang Formation) to the Enping (44 of 178, 24%) to the Zhuhai Formation (34 of 94, 36%) (Figures and ) and confirms that sediment contributed from regional sources increased through time.…”