Sequence stratigraphic framework of Late Paleozoic coal measures and their sedimentary evolution in Henan province

On the basis of field observation in the Late Paleozoic outcrops of Henan Province, combined with detailed drilling information, the sequence stratigraphic framework and sedimentary evolution characteristics of the Late Paleozoic coal measures in Henan Province were studied. The results show that the Late Paleozoic coal measures in the study area can be divided into one first-order sequence (308~252 Ma), and two second-order sequences(Ms₁, Ms₂) which are divided from the bottom surface of upper limestone unit of the Early Permian Taiyuan Formation, that is the regional sedimentary discontinuous interface. And based on the sequence interface characteristics, it can be further subdivided into 20 third-order sequences. In the early deposit stage of Benxi Formation within the study area, the transgression direction was from east to west, the transgression center migrated from south to north. In the later deposit stage of the Benxi Formation, the deposition of the following transgression expanded, and the transgression center moved further northward, the transgression direction was from NEE to SWW. Since the early deposit of Taiyuan Formation, the transgression gradually reached to the highest elevation, and the sea area expanded. Until the depositional stage of the Shanxi Formation, the scope of the sea area become smaller, regression to southeast, experienced a sedimentary evolution from shore-tidal-flat-lagoon to lower delta plain. In the depositional period from the Lower Shihezi Formation to the Upper Shihezi Formation, the seawater nearly receded from north China basin, so formed such a sedimentary evolution from delta-front-lower delta plain to upper delta plain in Henan province.