The study of tectono stratigraphic sequence and basin evolution in Shawan Sag

Junggar Basin

is of great signi-ficance both to the understanding of the basin structure and the petroleum exploration in this area

and to a certain extent to the understanding of the tectonic evolution of the Central Asian Orogenic Belt.Seismic and well data were integrated to perform fine tracing of seismic events

and to analyze the truncation

overlapping and pinch-out within each sequence deposited since the Carboniferous in combination of correlation on well-tie profiles

and finally six major tectonic sequences were recognized according to the corresponding tectonic regime transformation processes.Additionally

the fine interpretation of tectonics was based on the theory of fault-related folds

and the tectonic evolution of Shawan Sag since the Late Carboni-ferous was discussed mainly according to the fine interpretation and the balanced cross-section technique.The results show that the formation and evolution of the Shawan Sag can be divided into seven stages

namely the Late Carboniferous extensional fault depression

the Early Permian extensional depression

the Middle-Permian-to-Late-Triassic foreland basin

the Jurassic intracontinental depression and transpressional basin

the Cretaceous-to-Paleogene intracontinental depression

and the Neogene-to-Quaternary intracontinental foreland basin.The evolution is mainly controlled by multi-stage activities of the peripheral boundary fault zones.The strong transpression of the Hongche fault belt to the west boundary of the sag during the middle of Late Hercynian movement(P

2

)

Late Indosinian movement(T

3

)

and Middle-to-Late Yan-shanian movement(J

2

-E)

is the most powerful factor affecting the tectonic evolution and associated stratigraphic development and distribution in the sag.