Tectonic sequence stratigraphy and lithofacies paleogeography of Cretaceous-Paleogene in Sichuan Basin of China

Using the data of drilling and seismic prospecting,outcropping sedimentary facies observation and description,the authors recognize 4 unconformities and erosion hiatus surfaces,2 maximum flooding surfaces within the Cretaceous-Tertiary in Sichuan Basin of China.Further more,they divide the Cretaceous-Tertiary into 4 tectonic sequences and 6 sequences.The characteristics of the Cretaceous-Tertiary sedimentary framework and evolution are studied by tectonic sequence units.The study shows that from the earlier Early Cretaceous,Sichuan Basin has been effected by multi-times thrust nappes and tectonic emplacements of the periphery structure mountain system.Especially,the strongly squeezing action from southeast to northwest in the fault-fold belt of the southeast of Sichuan Basin has made the basin recession towards northwest and shrink from north to south and the sedimentary basin gradually to atrophy and die out,and finally the sedimentary history of the Sichuan foreland basin ended.In the early period(Early Cretaceous),the basin was opening and the southwest of Sichuan Basin was connected to the Xichang basin by channels.Later(the Late Cretaceous to the Tertiary period),the channels closed gradually,the basin sedimentary of an inland,dry and enclosed saline lakes appeared,and this has the sedimentary characteristics of an intramontane basin.