Structural Traps in Detachment Folds: a Case Study from the ‘Comb- and Trough-like’ Deformation Zone/s, East Sichuan, China

摘要

Detachment structures occur widely in the crust, and it is the commonest and most important deformation type developed in the region between erogenic belts and basins. The ‘comb-like’ and ‘toughlike’ fold belts in eastern Sichuan are caused by multi-layer detachment. The duplex structure is the most important deformation style in the region, exhibiting different characteristics from typical detachment structures. Different deformation styles, scales, and shortenings resulting from independent deformations of various detachment systems would lead to the phenomenon whereby most of the topographical heights in the region do not correspond to the structural heights in depth. Based on systematic structural analysis and combined with practical oil/gas prospecting, four types of structural traps are described from eastern Sichuan Province, which are: detachment and thrust trap; detachment folding trap; fault-flat blocking trap; and detachment layer trap. Meticulous studies on the deformation and distribution of detachment layers in the eastern Sichuan Province will contribute to oil/gas prospecting and selection of potential regions of marine-origin oil/gas prospecting in South China.