Eocene “provenance-channel-sink” analysis of Pearl River Mouth Basin: A case study of eastern Yangjiang Sag and Kaiping Sag

Taking the Eastern Yangjiang Sag and the Kaiping Sag as the research objects, we systematically analyzed the provenance, transport channels, and sedimentary facies of the Wenchang and Enping depositional periods by means of detrital zircon U-Pb dating and seismic profiles analysis, and then applies the idea of "provenance-channel-sink" to the Eocene sedimentary evolution of the Pearl River Mouth Basin. The U-Pb dating results of detrital zircons show that the provenance in the study area is heterogeneous in time and space. For the ages of detrital zircons from Wenchang Formation, the ones in the Eastern Yangjiang Sag mainly show a Yanshanian unimodal peak, while those in the Kaiping Sag display Yanshanian and Indosinian bimodal distributions. The zircons have good euhedral morphology, indicating the near-source deposition in the basin. The age spectra of detrital zircons from the Enping Formation show multimodal distributions. The number of older (Paleozoic and Precambrian) zircon grains increased and they are in higher roundness, indicating that the basin provenances had changed from near-source to far-sources. Based on a large number of seismic profiles, the transport channels such as fault trough, ancient gully, and structural transition zone were identified, which indicated that the strike slip of the Yangjiang-Yitong Fault Zone played an important role in transporting Eocene sediments in the study area. In addition, mainly littoral-shallow lacustrine facies, semi-deep lacustrine facies, and fan delta facies developed in the Wenchang depositional period, while braided river delta facies and littoral-shallow lake facies are more commonly observed during the Enping depositional period. This study is of great significance for understanding the Eocene "Provenance-Channel-Sink" process in the Eastern Yangjiang Sag and the Kaiping Sag, and the manifestations of the Yangjiang-Yitong fault zone in the Eocene.