Provenance analysis and geological significance of Paleocene in Lishui Sag, East China Sea Shelf Basin

Abstract

The provenance evolution of Paleocene is a main factor controlling the sedimentary filling characteristics of the East China Sea Shelf Basin, and is of great significance in the exploration and development of petro-bearing basins. Based on the core samples of the Paleocene of the Lishui Sag, East China Sea Shelf Basin, the systematic analysis of petrological and mineralogical characteristics was carried out. Through the study of the spatial and temporal distribution of sandstone clastic components, light and heavy mineral assemblages and related parameters, the evolution of the Paleocene provenance system in the study area and its significance for the sedimentary filling of the basin were discussed. The Paleocene clastic rocks in the Lishui Sag are mainly lithic feldspar sandstone, feldspar lithic sandstone and lithic sandstone. The sandstone is mainly moderately well-sorted, and the grains are mostly subangular or subrounded, with poor overall rounding, indicating that the structural maturity and compositional maturity are relatively lower. The light mineral assemblages of the Guifeng and Lingfeng formations of Peleocene are obviously different and show zoning features in different parts of the basin. In the central and northern parts of the western subsag, there are mainly parent rock types of cycle orogenic belts, while in the south of the western subsag, there are mainly parent rock types of cycle orogenic belts and magma arc. In the eastern subsag, there are mainly parent rock types of cycle orogenic belts. The characteristics of heavy mineral assemblages in the main horizons of the Paleocene in the study area change little. The Zhejiang-Fujian uplift belt in the west and the Yandang uplift in the east are the most important provenance areas of the Lishui Sag. The Lingfeng low uplift in the center of the basin suffered serious denudation before the deposition of the lower member of the Mingyuefeng Formation, providing local provenance for the basin. The provenance system analysis showed that when the Yueguifeng and Lingfeng formations were deposited, they were in the early and peak stages of fault depression, and the intra-basin provenance area was formed by the intra-basin fault uplift. As the upper member of the Lingfeng Formation was deposited, the basin entered the late stage of fault depression, local intra-basin provenance was no longer developed, and the main provenance system was extra-basin provenance.

Keywords

• petrological characteristics
• heavy mineral assemblage
• provenance analysis
• paleocene
• lishui sag
• east china sea shelf basin