Kinematic analysis of fault-slip data in the Nanling Tectonic Belt and Cretaceous to Paleogene tectonic evolution of the Central South China Block

Abstract

• Six tectonic events were inversed from fault-slip analysis in the Nanling Tectonic Belt. • Four Cretaceous tectonic events resulted from the Paleo-Pacific subduction . • Two Paleogene tectonic events were due to the far field effect of the India-Asia collision. Cretaceous tectonic events and Cenozoic geodynamics of the central South China Block are still under debate. A long-term extensional regime or two extension-contraction tectonic cycles were proposed for the Cretaceous tectonic evolution. While Cenozoic geodynamics of the central South China Block were ascribed to the Pacific subduction or the far field effect of the India-Asia collision. Kinematic analysis of fault-slip data were carried out for the Cretaceous to Paleogene Chaling-Yongxing Basin and the Lianshan-Yangshan Domain in the Nanling Tectonic Belt. Kinematic analysis of fault-slip data (409 groups of faults and striations) reveal four Cretaceous tectonic events and two Paleogene tectonic events. i) The early Early Cretaceous extensional regime is represented by a NW-SE horizontal minimum principal stress and a vertical maximum principal stress, which generated NE-striking boundary normal faults of Early Cretaceous basins. ii) The late Early Cretaceous strike-slip regime is characterized by a N-S horizontal maximum principal stress and a E-W horizontal minimum principal stress, which led to tectonic inversion of Early Cretaceous extensional basins and nearly N-S-striking folding of the Lower Cretaceous. iii) The early Late Cretaceous extensional regime is represented by a NW-SE horizontal minimum principal stress and a vertical maximum principal stress, which activated the NE-striking boundary normal faults of Late Cretaceous basins. And iv) the latest Late Cretaceous strike-slip regime is characterized by NW-SE horizontal maximum principal stress and a NE-SW horizontal minimum principal stress, which led to tectonic inversion of Late Cretaceous extensional basins and NNE-striking folding of the Upper Cretaceous. Orientations of maximum or minimum principal stresses imply that two extension-contraction tectonic cycles during the Cretaceous resulted from the Paleo-Pacific subduction. Two Paleogene tectonic events are v) the strike-slip regime characterized by NE-SW horizontal maximum principal stress and a NW-SE horizontal minimum principal stress, and vi) the subsequent extensional regime represented by a NE-SW minimum principal stress and a vertical maximum principal stress. The former generated NW-striking reverse faults and reactivated strike-slipping of NE- and NW-striking conjugate faults whereas the latter formed NW-striking normal faults in the Lower Paleogene clastic rocks. Orientations of maximum or minimum principal stresses indicate that two Paleogene tectonic events in the central South China Block were attributed to the far field effect of the India-Asia collision and subsequent stress relief.