摘要
The frequent upwarping and subsidence,and folding and uplifting of the earth crust caused by the isostatic adjustments and tectonic movements change the types of sediments in the basins frequently,and often cause the occurrence of multi-source formations in the geologic profile.As in the Tarim basin,during the first transgression in the early paleozoic,the deepest location was the Ordovician sag,in which deep marine clastic and carbonate rocks were deposited and main source rocks were included.In the late Paleozoic,it was the second transgression cycle,the thickest sedi-ments of Carboniferous-Permian were deposited in thie Awati sag and southwest sag which would be another major petroleum source rocks(Fig.2).
