Sedimentary successions and the onset of the Neoproterozoic Jiangnan sub-basin in the Nanhua rift, South China

Recent results of research from a regional geological survey have demonstrated that the Neoproterozoic Nanhuan strata in the Jiangnan sub-basin in the Nanhua rift in South China are built up of wedge-shaped strata, which rest transgressively on the metamorphic basement. These strata are grouped, as indicated by our sedimentary facies analysis, into the following four depositional successions (with ten related sedimentary facies associations): (1) continental volcanic depositional succession; (2) continental siliciclastic depositional succession; (3) marine siliciclastic depositional succession; and (4) glacial depositional succession. Compared with the Hunan-Guangxi sub-basin and the Northern Zhejiang sub-basin, the sedimentary processes in the Jiangnan sub-basin are dominated by continental rather than marine facies. However, similar sedimentary successions with identical facies trends can be recognized in all these sub-basins. All the Neoproterozoic basin fills in South China are characterized by a deepening water trend leading from continental to fully marine facies, recording the evolution of a typical rift basin related to the break-up of Rodinia. The crystalline zircons from a rhyolite sample taken from the base part of the first succession in the Jiangnan sub-basin give a mean SHRIMP U-Pb age of 803 +/- A 9 Ma. The occurrence of the ca. 803 Ma volcanic rocks and the volcaniclastic rocks marks the onset of a new phase of depositional cycles in the Jiangnan sub-basin.