Abstract:

The eastern South China continental block can be subdivided into the Yangtze block and the Cathaycian block. The Xuefengshan intracontinental tectonic system is one important part of the Yangtze block. The distribution of the unconformities between Triassic and Jurassic in the Xuefengshan tectonic system reveals four kinds of contact interfaces, including high-angle unconformity, low-angle unconformity, disconformity and conformity and becoming younger and younger to the west. Then the characteristics of Indosinian folds are also subdivided into two directions of fold axial traces in the South China, i.e. northeast-and northwest-striking folds, which were superimposed by the N-S-trending thrusts. The authors proposed that the longitudinal arcuate and northeastward structures in the Xuefengshan intracontiental tectonic system result from a control of different block borders under the same stress field as the previous one. The first-generation NEE-striking folds are rotated from the earlier NNE-striking folds due to late block rotating. The second-generation NNE-striking folds superimpose the NEE-striking folds. The intracontinental shortening between the Yangtze and Cathaysian blocks was earlier than the collision of the South China block with the Qinling-Dabie micro-continent. The Yangtze block and the Qinling-Dabie micro-continent had rotated in Early Indosinian orogeny. these resulted in a difference between those earlier structural lines formed in Early Triassic, the perpendicular relation to these structural lines was at last remained although they underwent small rotation between the Yangtze and Cathaysian blocks.

Key words: Indosinian movement, Triassic, South China, angular unconformity, Yangtze block, geology tectonics