Regionalization Of Mesozoic－Cenozoic Strata And Analysis Of Basin Evolution Of Sichuan Basin

The Sichuan continental basin was development from the Triassic craton basin, which basement was Palaeozoic-Early Triassic marine stratum, and cover was Late Triassic-Quaternary continental stratum. It is a important oil and gas bearing basin that own abundant hydrocarbon resources and great exploratory foreground.Based on the analysis and collation of sections, drillings, seismic and geochemical datum, this dissertation studied on the multi-stratigraphic classification and correlation, stratigraphic regionalization, filling characteristics and basin evolution of the Sichuan basin with the theories of palaeobiology, stratigraphy, sedimentology, tectonics and so on. First, on the achievement of predecessors, according to the stratic characteristics of the Sichuan basin, the lithostratigraphic unit and its characteristics with distribution range was clarified; the relationship between the lithostratigraphic unit and the chronostatigraphic unit was build; the isochronic strata framework of Mesozoic - Cenozoic was established. According to the isochronic strata framework, the thickness map of every period was drew; the filling characteristics was analyzed; the stratic sedimentary characteristics,the location of the center of depocencer and subsidence and their migration process was depicted in the Sichuan basin of Mesozoic-Cenozoic. Adoption to the principle of structural stratigraphic regionalization, according to the difference between the margin and the inner of the basin and the sedimentary difference in the basin, the stratic regions and subregions can separately regionalize in Triassic system, Jurassic system and Cretaceous- neogene system in the study area combination on the stages of the formation, the evolution, the suppression of the Sichuan basin. The Triassic system was divided into four regions and eleven subregions; the Jurassic system was divided into four regions and nine subregions; Cretaceous- neogene system was divided into five regions and nine subregions. At the same time, the stratic growing characteristics, the contact relationship, the hydrocarbon geology characteristics and the tectonic deformation was discussed in every subregion. On the basis of this, through the analysis of the stratic identities in the basin and the orogenic belt around the basin, the evolution of Sichuan basin was divided into six stages: the extensional stress control stage in the Early Triassic; the southeast compressional stress control stage in the Middle and later Triassic; the southwest compressional stress control stage in the Early and Middle Jurassic; the tectonic inactive stage in the early Late Jurassic; the two-way compressional stress control stage in the late late Jurassic and early Cretaceous; the southeast compressional stress control stage from the late Cretaceous to Quaternary. At the same time, the formation of the basin's northwest and northeast boundary was connected with the second episode of the Indosinian movement; the formation of the basin's southwest boundary and the latitudinal structure was connected with the third episode of the Yanshan movement; the formation of the basin's southeast boundary and the NW-NNW structure was connected with the first episode of Himalayan movement.