Source-to-sink transformation processes between closed setting, semiopen setting, and opening setting: A case study of the West-East China Sea from the Paleocene to the Eocene

Abstract

For complex convergence movements between the Pacific Plate and Eurasian Plate since the Cenozoic, the East China Sea Basin (ECSB) presents a three-stage rifting movement: initial rifting, rifting development, and structural reversal stages. The ECSB changed from a closed lacustrine to an open marine source-to-sink (S2S) system and then returned to a semiopen bay S2S system. Recently, research has attracted more attention to the relationship between the depositional setting evolution and the corresponding source-to-sink patterns. This study determines that the early Paleocene was dominated by a closed lacustrine setting according to water salinities based on trace element and micropalaeontological assemblages. The middle Paleocene had an open marine setting, and the late Paleocene and Eocene had semiopen bay settings. In addition, we rebuild the provenance area of the S2S system with detrital zircon UPb data and heavy mineral assemblage data to interpret the provenance from seismic profiles. During the early Paleocene, proximal sediments dominated the western depression zone of the East China Sea (WDZ), which was isolated by three sags. Integrated from core, well logging, and grain size data, the sediments in the routing system migrated to the prograding delta or alluvial fan. With statistics of the S2S parameters on the early Paleocene strata, sediment supply, average terrain height, and volume of the S2S system are analyzed from a bubble chart, which indicates that the average terrain height had a positive correlation with the S2S volume. For the middle Paleocene, more sediments from the Zhe-Min Caledonian fault belts on the western side distally migrated to the drainage basin and were deposited as tidally dominated deltas, reflecting an increasing reworking process. The statistical results show that the sediment supply was a dominant factor in the S2S system. As the regression proceeded, the S2S system developed in a semiopen bay setting in the late Paleocene and Eocene. A wave-dominated delta existed on the western side of the WDZ, and the eastern side developed subaqueous deltas. Moreover, we note that the sediment supply and average terrain height were important factors in developing the S2S system.