Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (2): 416-429.doi: 10.11743/ogg20210212

• Petroleum Geology • Previous Articles     Next Articles

Characteristics and genetic mechanism of tectonic deformation in basin-mountain transitional zone: A case study of Sangmuchang Anticline in southeastern Sichuan Basin

Jinhe Yang()   

  1. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2020-03-11 Online:2021-04-28 Published:2021-04-21

Abstract:

The Sangmuchang Anticline, sitting at a crucial location where the front of "trough-like" fold belt in western Hubei and Hunan Provinces superimposing the "barrier-style" fold belt in southeastern Sichuan Basin, was chosen to be studied to gain insight into the superimposition relationship between the belts as well as the tectonic deformation characteristics and genetic mechanisms of this mountain-basin transitional zone from Xuefeng Mountains to the Sichuan Basin.Available seismic and logging data together with DEM digital elevation and other related geological information were combined with fault-related fold theories to perform a fine interpretation of multiple 2D seismic sections crossing the anticline for architectural characterization and to establish a kinematics model with the balanced section restoration technique for tectonic evolution analysis.The study has concluded that the deformation of the anticline involves layered decollement with a mutual structural superposition in vertical direction, and that with some consistently deformed cap-rocks and bedding shear deformation dominating along the decollement surface, the overall structure of the anticline is under the joint influence of basement occurrence and Qiyueshan Fault.The fault is a concealed system formed by the combination of several basement thrusting faults striking near south-east, and the deep basement wedge and imbricated structures are thereby in superimposition, jointly controlling the anticline deformation.Further analysis shows that the anticline deformation initiated since the middle of Yanshan period, and its tectonic evolution has experienced the superposition of multiple tectonic movements.Under the westward thrusting of Xuefeng Mountains, the east-to-west progressive tectonic deformation of the west of Hunan and Hubei "trough-like" fold belt controls the activity of the deep tectonic wedges and the imbricated structures, which in turn control the main tectonic form of the anticline.The influence of the "partition-style" fold belt in the interior of the southeastern Sichuan Basin on the tectonic deformation of the dorsal basin-mountain transitional zone is mainly reflected in the anterior flank of the dorsal slope, resulting in the broad gentle fore wing and the steep narrow back wing of the anticline.

Key words: layered decollement deformation, geological architecture, structural evolution, Qiyueshan Fault, basin-mountain transitional zone, Sichuan Basin

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