Energy Geoscience (Oct 2022)
A new understanding of Jurassic provenance and sedimentary framework in northwestern Sikeshu Sag, Junggar Basin, China
Abstract
For a basin or sag with low exploration maturity, the understanding of its provenance system and clastic distribution system is the key to the analysis of its sedimentary framework and further influence the decision making and deployment of exploration. This study analyzed the Jurassic provenance of the Sikeshu Sag based on the data from cores, well logging, and seismic survey. The analysis of seismic profile characteristics revealed that there is a remote possibility that the Chepaizi Uplift in the northern part serves as the main Jurassic provenance of the Sikeshu Sag. On the contrary, systematic indicative signs of provenance have developed in the study area, including west-to-east progradational reflection configurations and composite mounded reflections that show bi-directional downlapping contact in both the south and north directions. These systematic indicative signs suggest that the denuded uplift area in the western part is the main Jurassic provenance in the study area. Controlled by the provenance in the western part, the study area shows an orderly distribution of paleosedimentary systems from west to east and from shallow to deep water. The paleosedimentary system mainly exhibits the following characteristics after undergoing later high-intensity transformation. (1) The western part is dominated by the subfacies of a braided river delta front and is composed of three microfacies including distributary channels, interdistributary bays, and sandbars; (2) The middle and eastern parts show a semi-deep lacustrine environment, where debris flow sedimentary systems of slumping origin or in deep canyons, gullies and channels connected to the denudation area developed from west to east. These debris flow sedimentary systems jointly form the clastic sedimentary system under the control of western provenance.
