PALEOSTRESS REGIME EVOLUTION IN SOUTH CHINA INDUCED BY DYNAMIC CHANGES IN IZANAGI-PACIFIC SUBDUCTION SINCE THE CRETACEOUS

A complex intraplate deformation sequence since the Cretaceous is recorded in the basin-mountain belt along the South China continental margin and provides a critical window to reconstruct the paleostress regime since the Cretaceous and further explore the relationship between the intraplate deformation evolution of South China and the dynamic changes in Izanagi-Pacific subduction. Here, integrating the clues from the field investigation, fault-slip inversion, and zircon U-Pb chronology in four regions along the basin-mountain belt reveals six paleostress regimes on the South China margin, listed in order of decreasing age: E-W extension (ca. 145-120 Ma), NW-SE extension (ca. 120-105 Ma), NW-SE compression (ca. 105-100 Ma), N-S extension (ca. 100-65 Ma), NE-SW compression (ca. 65-55 Ma), and NE-SW extension (ca. < 55 Ma). The four extensional regimes controlled synchronous deposition, resulting in NW-striking and E-W-striking alignments of Early and Late Cretaceous basins, respectively. In comparison, the two compressional regimes produced two regional unconformities between the strata of the Early and Late Cretaceous and between the strata of the Late Cretaceous and the Paleogene. Our results suggest that the Cretaceous extension prevalent in South China should have started at ca. 145 Ma, reversed to short-term compression, and restarted at ca. 100 Ma. By comparison with the history of the Izanagi-Pacific plate subduction, the dynamic changes in the subduction process are the first-order driving force of intraplate deformation since the Cretaceous in South China.