RELATIONS BETWEEN EVOLUTION OF SEDIMENTARY CYCLES AND TECTONIC UPLIFT AROUND SICHUAN BASIN FROM JURASSIC TO EARLY CRETACEOUS

Sedimentary facies and paleontology are synthetically analyzed in order to clarify the evolution and paleo climate of Shichuan basin during Jurassic and Cretaceous. The study shows that the tectogenesis around the basin can be divided into two cycles during Jurassic and Cretaceous. One began from Early Jurassic and ended in Middle Jurassic and the other one from Late Jurassic to Early Cretaceous. The basin was widely covered by mudstone, sandstone and shell limestone of lake facies in the early stage of the above two cycles. The thickness is relatively small and the sedimentary particles are much more fine grained both in the early stage of the two cycles, showing that the tectogenesis is relatively stable. However, in the late stage the basin is characterized by widely spread varicolored thick sandstone, mudstone and conglomerate of river or alluvial fan facies. Even more, there are usually sediments and coarse sedimentary particles of large thickness in the late stages, reflecting rapid uplift of the mountains around the basin. According to the study of sedimentation and fossils, Sichuan basin should have a warm climate during the first cycle and hot climate from the beginning of the second cycle.