Early–middle Jurassic source to sink evolution and its tectonic significance in the northeastern Sichuan Basin

Abstract

This paper discusses the sedimentary environment and source supply in the sedimentary area and their coupling relationship through a detailed description of the deposits from the Ziliujing Formation to Shaximiao Formation of the Lower–Middle Jurassic on the Tieshan section in the Dazhou City, northeastern Sichuan Province, through sedimentary characterization, determination of the paleocurrent direction, analysis of heavy minerals, and detrital zircon U–Pb dating. The results show that the Zhenzhuchong Member is sufficiently supplied with detrital sediments and is dominantly composed of fluvial-delta deposits. The Dongyuemiao Member—the first member of the Lianggaoshan Formation—is dominated by lacustrine deposits, with the detrital supply increased initially in the early Lianggaoshan. The second member of the Lianggaoshan Formation suggests a significant increase in detrital supply, with shrunken lake basin and changed paleocurrent direction. The Shaximiao Formation reveals a complete disappearance of the lake basin in the northern Sichuan Basin. The comprehensive analysis on source supply indicates that the change in source property is apparently coupled with the change in the sedimentary environment, both controlled by orogenesis around the basin. It is inferred from the zircon age distribution that the changes in the sedimentary environment and source supply during the late Ziliujing period and the middle and late Lianggaoshan period resulted from the uplifting of the Micangshan Mountain, Dabashan Mountain, and Qinling Mountain, respectively.