Abstract

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Title:: Superimposed Fold Characteristics and Tectonic Evolution in Huize Area of Northeastern Yunnan, China

Author(s):: LIU Lang; LI Zhi-wei; SHAO Jun-qi; HUANG Jin-shan; LIU De-min; LYU Xiao-chun; 1. School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China; 2. Guangdong Nuclear Force Institute of Engineering Investigation, Guangzhou 510800, Guangdong, China; 3. No.10 Gold Geological Party of Chinese People’s Armed Police Force, Kunming 650001, Yunnan, China

Keywords:: superimposed fold; tectonic evolution; fault adjustment; structural analysis; stress field; Yangtze block; Yunnan

Abstract:: Huize area in northeastern Yunnan is located on the southwest of Yangtze block, and outcrops Xiaomiluo superimposed fold. The fold is developed in the triangle area confined by Xiaojiang, Huize and Yulu faults, showing a “bow” shaped distribution. The stress field indicates that the syncline experiences a modification from a nearly SN-trending axis to a complex “bow” shape. Based on the detailed field analysis of Huize and Yulu faults, it is found that Huize fault undergoes transformations from compression to dextral transpression and then to sinistral transpression, while Yulu fault experiences an evolution from compression to dextral transpression. The characteristics of stress field show that faults adjust in response to the regional stress field, and Huize area undergoes compression in near EW-, NW-, and NE-trending directions successively. The strata contact relationship between Huize and surrounding areas along with the ESR chronological characteristics of Cenozoic sedimentary basin, determines that the superimposed fold occurs in Late Eocene(25-38 Ma), and is superposed in Late Oligocene (17.8±1.7)Ma) and Pleistocene (0.75-1.05 Ma), respectively.