Stratigraphic classification and correlation and sedimentary environment analysis of the Early Triassic in western Pingxiang-Leping depression, Jiangxi Province

Pingxiang-Yichun area is located in western Pingxiang-Leping depression, where the Early Triassic strata are developed extensively. The stratigraphic nomenclature, age, distribution, and the classification of the stratigraphic units in this area have been controversial for a long time, which considerably hinders the study of the Pingxiang-Leping depression. Through a 1:50000 regional geological survey in Pingxiang - Yichun area , the authors systematically classified the Early Triassic strata of that area for the first time on the basis of investigating lithostratigraphy and biostratigraphy. The Early Triassic strata in the area can be divided in upward sucession into Yinkeng, Qinglong and Zhouchongcun Formations, and the Zhouchongcun Formation can be further subdivided into four members. On the basis of conodont data, the Yinkeng Formation, the Qinglong Formation, and the first member of the Zhouchongcun Formation are assigned to India Stage, and the second member to the fourth member of the Zhouchongcun Formation are assigned to Olenekian Stage. At the same time, according to the characteristics of the lithologic association and sedimentary facies, an analysis of the sedimentary environment was carried out. The sedimentary environment of the Early Triassic strata in the study area was "terrace-continental slope-basin" epicontinental sea with the ancient landform structure.