Using seismic geomorphology and detrital zircon geochronology to constrain provenance evolution and its response of Paleogene Enping Formation in the Baiyun Sag, Pearl River Mouth Basin, South China sea: Implications for paleo-Pearl River drainage evolution

The syn-rift sedimentary history of the Pearl River Mouth Basin (PRMB) in the northern South China Sea is poorly understood due to restricted borehole coverage. In this study, an integrated analysis of 3D seismic data, detrital zircon data and the data from previous provenance studies has been used to document the shifting of provenance and depositional response during the Paleogene Enping Formation of the Baiyun Sag in the PRMB. Our results show that the Baiyun Sag was filled mainly with sediments derived from two potential sources: the intrabasinal source of uplifts in the PRMB (Mesozoic igneous rocks) and the extrabasinal source of the South China Block (Precambrian-Paleozoic metamorphic and magmatic rocks). During the deposition of the lower and middle members of the Enping Formation (Ep(L)-Ep(M)), the sediment of the Baiyun Sag was derived primarily from the intrabasinal source. The sediment was transported over relatively short distance through faulted troughs and incised valleys and deposited in a series of small-to medium-scale braided deltas, beach bars and fan deltas. However, during the deposition of the upper member of the Enping Formation (Ep(U)), the sediment of the Baiyun Sag was derived mainly from a mixture of extrabasinal and intrabasinal sources. The sediment of the Ep(u) was transported over relatively long distance via large-scale incised valleys and deposited in three stages large-scale progradational braided delta. The detrital zircon age spectra of the Ep u in the northwestern area show four well-recognized age clusters with peaks at similar to 842 Ma, similar to 450 Ma, similar to 252 Ma and similar to 151 Ma, which correspond to tectono-magmatism in the South China Block. The analysis of provenance shifting in this study may be of great value in constraining the tectonic and sedimentary evolution of the PRMB, northern South China Sea margin, as well as the drainage evolution of the paleo-Pearl River. Our findings can also provide potential benefits for the integrated analysis of geophysics and geochronology data through time in the petroliferous basins.