Late Paleozoic sedimentation and tectonics of rift and limited ocean basin at southern margin of the Qinling

The rifting and occurrence of limited oceanic basin at southern margin of Qinling separated south Qinling from Yangtze Block in late Paleozoic. Detailed sedimentary studies were carried out at two localities at southern flank of this rift-limited oceanic basin zone. and depositional architectures were then established accordingly. The results show that tectono-sedimentary stories are differing in different positions but clearly demonstrate spatial development of the rift. It is obvious that the rift in west part of Mianlue underwent two developmentary phases, early rapid subsidence and late slow subsidence, and there occurred breakup unconformity between the seccessions of the two subsidence phases. Combined with the data of structural, geochemical and chronological studies on the ophiolitic complex within the Mianlue zone. it is demonstrated that the rifting-drifting transition occurred, leading to the development of limited oceanic basin during the late Paleazoic. Spatial and temporal evolution of the