BIOSTRATIGRAPHIC DIVISION AND REGIONAL CORRELATION OF WUFENG FORMATION AND LONGMAXI FORMATION IN JINKECUN SECTION, SOUTHWESTERN MARGIN OF SICHUAN BASIN

To explore the sedimentary environment of Upper Yangtze Basin at the turn of Ordovician-Silurian period and determine the sedimentary horizon of organic shale in Junlian area on the southwestern margin of Sichuan Basin, nine continuous biozones and combinations from Late Ordovician Katian WF2 zone to Early Silurian Aeronian LM6 zone are identified based on the study of lithostratigraphy and biostratigraphy of Wufeng Formation-Longmaxi Formation in Jinkecun section. It is believed that Jinkecun area is the first to enter the foreland period in the Upper Yangtze Basin, in the time of Rhuddanian LM1 stage. The biostratigraphic correlation between Jinkecun section and XD-2, N-211 and W-202 wells on the north indicates that the upper limit of black shale graptolite zone extends from LM6 to LM9 from south to north, showing a gradually increasing trend. The organic-rich shale in Jinkcun section is located in WF2-LM4 zones with a thickness of 20.6 m, which provides basic data for shale gas exploration and development in the area.