Quaternary sedimentary sequence and sedimentary environment restoration in the Jinzhong Basin, Fenhe Rift Valley

Abstract

Jinzhong Basin is a Cenozoic intracontinental faulted sedimentary basin located in the middle of Fen-Wei graben system. Our study aims to identify the Quaternary sedimentary sequence and reveal the Quaternary sedimentary environmental evolution of the Jinzhong Basin. We used structural petrography to survey the Quaternary sediments and sedimentary environment on the surface and in the boreholes of the Jinzhong Basin. The results shows: The surface Quaternary sedimentary sequence in the Qingxu area of the Jinzhong Basin is composed of the river bed facies and floodplain facies of the Tuoyang Formation in the basin-the fluvial facies of the Fenhe Formation at the basin edge-the fluvial facies of the Zhiyu Formation, alluvial fan facies of the Fenhe Formation and aeolian facies of the Malan Formation in the basin-mountain transition zone-Permian neritic facies in the bedrock mountain (the periphery of the basin). The Quaternary sedimentary sequence in the core of the borehole is composed of the shallow lake facies and lakeside facies of the Lower Pleistocene-the shallow lake facies and fluvial facies of the Middle Pleistocene-the fluvial facies and alluvial fan facies of the Upper Pleistocene-the alluvial fan facies of the Holocene. The study suggests that the sedimentary sequence and environmental evolution of the Jinzhong basin is the early Pleistocene continental lake basin sediment-the Middle Pleistocene shrunken lake-the late Pleistocene strongly shrunken lake and river-the Holocene re-subsidence terrestrial lake pots. From the center to the mountain the sedimentary environment of the continental lake basin can be divided into lake sediment-river and lake sediment-alluvial fan sediment(the mountain mouth area at the edge of the basin).The dislocation of Upper Pleistocene sediments in the basin-mountain transition zone was caused by syn-sedimentary active faults. The fault activity reveals the dynamic mechanism of stepped formation in the Jinzhong Basin. These findings provide new evidence for the study of regional climate, environmental changes and regional tectonics in the Jinzhong Basin as well as reference for the site selection of Taiyuan City.

Keywords

• jinzhong basin
• quaternary
• sedimentary sequence
• sedimentary environment
• active fault