Source to sink transport in the Oligocene Huagang Formation of the Xihu Depression, East China Sea Shelf Basin

Abstract

The Huagang Formation is the most important hydrocarbon reservoir in the Xihu Depression of the East China Sea Shelf Basin. Reconstructing the provenance and transport pathways of its main sand bodies is of great significance to oil and gas exploration. Previous provenance studies were mainly based on heavy mineral analyses and showed multiple source areas, but so far quantitative estimates on provenance are lacking. Detrital zircon U–Pb dating combined with heavy mineral analysis is an effective tool to quantitatively investigate sediment provenance. In this paper, we use the LA-ICP-MS method for U-Pb dating of detrital zircons of 18 samples from 13 drill cores in the Xihu Depression to determine the sediment provenance of the Oligocene Huagang sandstones. The U-Pb zircon dating results show three different age groups, in which Precambrian ages dominate (∼60%), and Paleozoic and Mesozoic ages each account for ∼20%. The Precambrian zircons are mainly derived from the Hupijiao uplift, which indicates a dominant and long-distance north to south transport direction. The provenance of the Paleozoic zircons is mainly from the Diaoyu Islands Folded-Uplift Belt in the east, while the Haijiao and Yushan uplifts in the west are the main source region for the Mesozoic zircons. The northern provenance transport pathway is dominated by axial channels. Incised valleys are observed in the western source and a transfer zone dominates the eastern provenance. The integration of all data results in a new schematic model of source to sink transport in the Huagang sandstones, demonstrating the complexity of multiple source rocks and sediment transport pathways in the Oligocene Xihu Depression.