Cenozoic sedimentary systems and their tectonic-sedimentary evolution in southern uplift zone of the Qiongdongnan Basin

The back-arc spreading of the Neo-Tethys resulted in the consumption of the Palaeo-South China Sea and the spreading of the Neo-South China Sea. Subsequent separation of Xisha and Zhongsha microcontinental masses from the South China Continental margin gave rise to the formation and continuous subsidence of the Qiongdongnan Basin. During the deposition of the Yacheng Formation in the southern uplift zone of the Qiongdongnan Basin, the filling-up prevailed over the Basin, and then resulted in the development of the fan delta-shallow shelf sedimentary systems near the source areas. The principal source of detritus lay to the Songnan low uplift and the southern uplift denudational areas. Till the deposition of the Lingshui Formation-Meishan Formation, the combination of tectonic subsidence and global sea-level rising resulted in the expansion of the transgressions, and the development of the shallow shelf deposits in the southern uplift zone. The isolated carbonate platform organic reefs were once developed only in the Xisha (Yongle) uplift zone. The tectonic-sedimentary evolution of the Qiongdongnan Basin and its southern uplift zone took place under the tectonic background of the continuous subsidence of the Basin caused by the consumption of the Palaeo-South China Sea and the spreading of the Neo-South China Sea, as well as the strong influence of the global sea-level falling on the littoral-shallow shelf denudation and filling-up.