关键词: 小江断裂系, 川滇地块, 滇中高原, 楚雄盆地, 背形构造, 向形构造

Abstract: Under continuous N-S convergence between the Indian and Eurasian continents, the Sichuan-Yunnan block on the southeastern margin of the Tibetan Plateau has undergone southeastward extrusion and clockwise rotation since late Cenozoic along the right-lateral Red River to the southwest and left-lateral Xianshuihe-Xiaojiang Fault systems to the northeast. However, the surface deformation along the front part of the block in central Yunnan, where the Red River and Xianshuihe-Xiaojiang Fault systems join each other, is characterized by transtension instead of transpression, as indicated by the presence of a series of grabens and horsts along the Xiaojiang Fault system, penetrating the central Yunnan antiform in N-S direction. To explain such contradiction between the field data and theoretical modeling, a mechanic model is constructed in this study, based on the geologic and geomorphic features of the central Yunnan antiform, and the results illustrate that the generation of the E-W extension occurring along the Xiaojiang Fault strands is predominated by stress and strain patterns across the antiform.

Key words: Xiaojiang Fault system, Chuandian block, central Yunnan Plateau, Chuxiong Basin, antiform, synform