Mesozoic-Cenozoic Basin Features and Evolution of Southeast China

The Late Triassic to Paleogene(T-E) basin occupies an area of 143100 km~2,being the sixth area of the whole of SE China;the total area of synchronous granitoid is about 127300 km~2;it provides a key for understanding the tectonic evolution of South China.From a new 1:1500000 geological map of the Mesozoic-Cenozoic basins of SE China,combined with analysis of geometrical and petrological features,some new insights of basin tectonics are obtained.Advances include petrotectonic assemblages, basin classification of geodynamics,geometric features,relations of basin and range.According to basin-forming geodynamicai mechanisms,the Mesozoic-Cenozoic basin of SE China can be divided into three types,namely:1) para-foreland basin formed from Late Triassic to Early Jurassic(T-J) under compressional conditions;2) rift basins formed during the Middle Jurassic(J) under a strongly extensional setting;and 3) a faulted depression formed during Early Cretaceous to Paleogene (K-E) under back-arc extension action.From the rock assemblages of the basin,the faulted depression can be subdivided into a volcanic-sedimentary type formed mainly during the Early Cretaceous(K) and a red -bed type formed from Late Cretaceous to Paleogene(K-E).Statistical data suggest that the area of all para-foreland basins(T-J) is 15120 km~2,one of rift basins(J) occupies 4640 km~2,and all faulted depressions equal to 124330 km~2 including the K-E red-bed basins of 37850 km~2.The Early Mesozoic (T-J) basin and granite were mostly co-generated under a post-collision compression background, while the basins from Middle Jurassic to Paleogene(J-E) were mainly constrained by regional extensional tectonics.Three geological and geographical zones were surveyed,namely:1)the Wuyishan separating zone of paleogeography and climate from Middle Jurassic to Tertiary;2)the Middle Jurassic rift zone;and 3)the Ganjiang separating zone of Late Mesozoic volcanism.Three types of basin-granite relationships have been identified,including compressional(a few),strike-slip(a few), and extensional(common).A three-stage geodynamical evolution of the SE-China basin is mooted:an Early Mesozoic basin-granite framework;a transitional Middle Jurassic tectonic regime; intracontinental extension and red-bed faulted depressions since the Late Cretaceous.