Abstract:

During late Indo-Sinian epoch and middle Yanshan epoch, the Mesozoic and Paleozoic in Lower Yangtze region in Jiangsu changed from a stable oceanic-continental plate tectonic system into an intraplate deformation system,resulting in a ramp thrust tectonic framework with NW to SE thrusting in northern Jiangsu and SE to NW thrusting in southern Jiangsu.In northern Jiangsu, the Sinian and Lower Paleozoic overthrusted along the Doushantuo Formation and a subsidiary detachment;while in southern Jiangsu,the Upper Paleozoic overthrusted along the Gaojiabian Formation detachment,and the Lower Paleozoic became duplex thrust structure under the control of the two detachments.In middle Yanshan epoch,NNE left lateral compresso shear and NW right-lateral compresso-shear strike-slip movements modified the former thrust structures.In late Yanshan epoch,the regional stress setting turned into NE-SE extensional environment,in which the overthrust nappe slipped back along fault ramps under gravitational force,resulting in a half graben like fault depression.While in southern Jiangsu,the Lower Paleozoic duplex thrust structure and the Upper Paleozoic thrusting over Silurian made it difficult to slip back, due to limited potential energy of vertical displacement.The uplifting in late Himalayan epoch finally led to the tectonic framework of Mesozoic Paleozoic being high in southern Jiangsu and low in northern Jiangsu.

Key words: Mesozoic, Paleozoic, intraplate deformation system, ramp tectonic framework, overthrust nappe, duplex thrust structure, strike slip fault