SEDIMENTARY FILLING EVOLUTION OF CHENGDU BASIN IN LATE CENOZOIC

Chengdu Basin, a continental sedimentary basin between Longmenshan tectonic belt and Longquanshan fold fault belt, is filled with huge thick Late Cenozoic semi-consolidated and loose sediments. Based on the analysis of sedimentary characteristics and filling process of the basin, it is considered that there are twice sedimentary-tectonic transformations and changes in accommodation space during the sedimentary process, which leads to the migration of sedimentary center from the front of Longmenshan thrust tectonic belt to the footwall area of Dayi-Pengzhou fault belt. The sedimentary characteristics show that the basin is mainly alluvial fan and fluvial facies. The Pliocene Dayi conglomerate stage is dominated by alluvial fan facies, distributed only on the west of Pujiang-Xinjin-Chengdu-Deyang line. During the Early-Middle Pleistocene, alluvial fan and fluvial facies deposits are predominant, with the west of Pujiang-Xinjin-Chengdu-Deyang line as the alluvial fan area and the east as the fluvial facies area. The Late Pleistocene-Holocene is mainly fluvial deposits, but the sediment sources and drainage characteristics between the east and west areas are obviously different. The study may provide a basis for 3D geological structure modeling of underground space, potential evaluation of underground space resources, as well as occurrence horizon of mineral and human resources in Chengdu City.