Surface and Deep Structure of the Hanshan-Wuwei Basins in the Lower Yangtze Region: Implications for Mesozoic Tectonic Evolution of the South China Block

Indicating the tectonic features of the Hanshan-Wuwei basin can reconstruct the framework of the basins formed in Mesozoic and further understand the Mesozoic tectonic evolution of the South China Block. Studies on surface structure, regional stress field and deep geophysical characteristics of the Mesozoic Hanshan-Wuwei basin in Lower Yangtze region were carried out. NE-NNE trending folds and faults developed in the northern margin of the basins. The reconstruction of tectonic stress fields indicates four stress stages dominating the basins' evolution including NW-SE compression, N-S compression, NW-SE extension and NWW-SEE compression. 2D seismic profiles reveal coexistence of thrust, strike-slip and normal faults in the basin. Combined with regional geological studies, the geodynamic processes for the formation of the Hanshan-Wuwei basin can be divided into five stages: 1) During the Late Triassic, EW trending foreland basin was formed by N-S compression; 2) From Mid-Jurassic to Late Jurassic, continuous compression strengthened the foreland deformation and formed thrust nappes. In this stage, the integrated foreland basin was compartmentalized or fragmented, and transferred to the broken foreland basin; 3) NE-trending sinistral strike-slip movement at the beginning of the Early Cretaceous; 4) Regional extension resulted in normal faults and rift basins developing in the Late Cretaceous; 5) The NWW-SEE compression at the end of the Late Cretaceous caused NW sinistral strike-slip faults to form, which partly transformed the rift basin.