Abstract:

The Subei Basin is a typical dustpan-shaped fault depression composed vertically of three layers,i.e.,a downwarped basin deposit(K2t-E1f),a fault depression basin deposit(E2d-E2s) and a tilt-block basin deposit(N1-2y).The basin had gone through three episodes of uplifting and is a relic basin formed in the late Early Tertiary.It also developed some fault combinations of different types and NE-and NW-trending structures.This paper documents a discussion on the forming mechanism of the dust-shaped fault depression,and comes to the conclusion that the tilting in the depression is the least likely to be caused by "rotation",and that the numerous extensional faults were resulted from the early reverse faulting of the basement and the reversing of force couple.The present dustpan-shaped basin is the result of deposition or uplifting and erosion when experiencing extension,faulted depression and compression at the same direction,alternating with basement uplifting.The dynamic of the extension and compression mainly came from the subduction and collision of the India Plate and the Pacific-Philippine plate to the Eurasia.With the two forces alternatively working on the eastern China,an "accordion-like" stress field(with extension and compression alternated) was formed in the NW direction,resulting in the dustpan-shaped basin

Key words: basin-forming kinetics, right lateral shear, left-lateral shear, complex small fault-block, relic basin, faulted basin, dustpan-shaped depression, Subei Basin