Abstract:

Normal faults that controlled the formation and evolution of the Meso-Cenozoic fault-deressed basins in East China appear to be compresso-shear X-shaped faults which resulted from horizontal compression of the Kula andIndia Plates and crustal gravity.They are developed from the depths of crustand possessed behaviours of compression and translation. Since the Cretaceous, especially the Eocene epoch, the mainland of Chinawas compressed by northeastward compression from the Xilong Projectivebody of the India Plate, thus a series of northeast convex-arc compressedzones were formed in southwest China on the north and east sides of thezones, a compresso-shear structural belt was resulted respectively to consti-tute a huge X-shaped structure in plane. The north sinictral shearing belt runsalong a line of west Kulun, Altun, Yinshan and Yanshan Mountains in NEEstretch; the east belt with evidences of dextral shearing extends from theBeibu Gulf in the south to Yilan-Yitong in the north throuogh Hunan and theNorth China Plain in NNE striking. Once the upper crust overlying the middle and lower plastic ones of thecrust breaks, stress state on the hanging wall respoding to a cantilever withboth underlying plastic materials as elastic base and the fault plane as freeend under the combined efforts of both its own gravity and planar sliding.As a consequence, the nearer to the fault plane, the greater the subsidingamplitude, thus forming a listric basin. The basement of the basin subsidedcontinuously to cause the underlying plastic materials to flow towards theheading wall or the elevated end of the hanging wall, which resulted in thestructural framework of uplifts associated with basins. When the crust becamethinner due to the lateral translation of the plastic materials beneath thebasin, the asthenosphere materials must be upwarped and the lower materialsof the lithosphere were compressed towards sides under gravity equilibrium,making the top surface of the asthenosphere to be mirror symmetrical to thebottom surface of the basin. Therefore, not that mantle diapirism is the causeof the formation of faulted basin but that the result of the formation. Theabove mentioned inference is also supported by earthquake activities.