Structural Analysis of the Multi‐layer Detachment Folding in Eastern Sichuan Province

Abstract: A serial of “comb‐like and trough‐like” folds developed in eastern Sichuan, controlled by the multi‐layer detachment folding, is different from the classical Jura‐type structure in their development. The key factor resulting in the development of these structures is the occurrence of detachment layers in different parts of Neoprotozoic to Mesozoic stratigraphy of study area, which, from the bottom to the top, are the lower part of Banxi Group, Lower Cambrian (Niutitang Formation), Lower Silurian (Longmaxi Formation and Luoreping Formation), Upper Permian (Wujiaping Formation) and Lower Triassic (Daye Formation). On the basis of field survey combined with sand‐box modeling, this study argued that the detachment layer of the lower part of Banxi Group controlled the development of the “comb‐like” folds, and the lower part of Cambrian detachment layer controlled the development of “trough‐like” folds. Because of several detachment layers occurring in the study area, the development of duplex structures different scales is an important deformation mechanism, and the duplexes are the important structures distinguished from the typical detachment folding structures. Due to these duplexes, the surface structures and structural highs may not be the structural highs in the depth. Meanwhile, the detachment layers are good channels for oil/gas migration benefiting the understanding of accumulation and migration of oil and gas.