Features and controlling factors of source-to-sink system during the fault-depression transition in a marine rift basin: A case study of Paleogene Oligocene Lingshui Formation in Qiongdongnan Basin, China

Guided by the analysis of source-to-sink system, this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrating outcrop, core, drilling, logging and 3D seismic data, to systematically analyze the characteristics of the source, transport pathway, and sink during the deposition of Lingshui Formation, and reveal the patterns, controlling factors and petroleum geologic significance of the source-to-sink systems. The results are obtained in five aspects. First, during the fault-depression transition, the Qiongdongnan Basin received sediments from the provenances presenting as segments in east-west and zones in north-south, primarily with the Indosinian granites in the Shenhu Uplift in the east and the Yanshanian granites in the west. Overall, the sources are young in the southern and northern parts and old in the interior of the basin. Second, three types of sediment transport pathways are identified: paleo-valleys, fault troughs and trough-valley transitional zones. Third, based on differences in sediment supply modes, the unique source-to-sink systems during the fault-depression transition in marine rift basins are categorized into three types: exogenous, endogenous and composite. Fourth, the characteristics of these source-to-sink systems are primarily controlled by provenance, paleogeomorphology, and sea-level changes. Provenance lithology and scale dictated the composition and volume of sedimentary deposits. Paleogeomorphology influenced erosion intensity in the provenance and the development of paleodrainage systems, thereby affecting the distribution and types of sedimentary systems. Additionally, sea-level changes decided the extent of the provenance, but also regulated the sediment distribution patterns through oceanic processes such as waves and tides. Fifth, the exogenous source-to-sink systems may form large-scale reservoir bodies, the endogenous systems develop secondary pores due to presence of soluble minerals, and the composite systems demonstrate reservoir properties varying from area to area.