Sedimentary environments and its geological significance of Jurassic Moshan Formation in the northeastern margin of Dabie Mountain

Jurassic is an important period in basin-mountain coupling studies between Dabie orogenic belt and adjacent basins. The Jurassic strata on the periphery of Dabie Mountain provide well constraints on the orogenic processes of Dabie Mountain and the exhumation and uproofing of deep subduction rocks. This paper chooses Jurassic Moshan Formation in Yueshan area of Anqing in the northeastern margin of Dabie Mountain as the study object. Fine analysis of grain size, detrital composition, heavy mineral assemblages and U-Pb isotope chronologic dating of detrital zircons are carried out on clastic rocks of Moshan Formation. The lithological and sedimentary characteristics and result of grain size analysis all indicated sedimentary environment of clastic rocks of Moshan Formation is fan delta front subaqueous distributary channels. Results of detrital composition, heavy mineral assemblages and U-Pb isotope chronologic dating suggest that the provenance of clastic rocks are mostly derived from South China Plate, and Susong complex in Dabie orogenic belt also provide a small amount of detritus. The lack of garnets and Triassic metamorphic zircons suggest that the high pressure-ultrahigh pressure metamorphic rocks may have not been exposed to the surface in the Early Jurassic.