Cretaceous magnetic fabric characteristics of the South China Block and its tectonic response to the Pacific-Tethys dual tectonic domains

The Cretaceous tectonic evolution of the South China Block was jointly influenced by the Pacific and Tethys dual tectonic domains. Existing research on the Cretaceous tectonic evolution of South China mainly focuses on regions with intense intracontinental deformation, while the tectonic characteristics of weakly deformed areas remain poorly understood. This lack of data limits our ability to spatially constrain the extent, orientation, and magnitude of the far-field stress regime imposed on the South China Block by the Pacific-Tethys dual tectonic domains since the Cretaceous, thereby restricting a comprehensive understanding of the block′s tectonic response during different evolutionary stages. This study investigates the magnetic fabric (Anisotropy of Magnetic Susceptibility, AMS) of Cretaceous sedimentary strata in the eastern Sichuan fold-and-thrust belt, integrates existing AMS data from the South China Block, and combined with the regional tectonic framework, elucidates the coupling mechanisms by which the Pacific-Tethys dual tectonic domains influenced South China's tectonic evolution during the Cretaceous. The results indicate that the Huaying Shan fault zone represented a stress boundary between the Tethys and Pacific tectonic domains during the Cretaceous. Specifically, the closure of the Meso-Neotethys Ocean and subsequent intracontinental shortening controlled the tectonic evolution west of the Huaying Shan fault zone. Meanwhile, the Izanagi and paleo-Philippine Sea plates jointly constituted the western margin of the paleo-Pacific domain, and both subducted continuously beneath the eastern margin of Eurasia during the Cretaceous. The subduction of the Izanagi Plate underwent multiple episodes of high-angle reorientation. When superimposed on the cyclic ‘multi-stage subduction initiation–slab rollback’ process associated with the paleo-Philippine Sea Plate, this gave rise to a dual dynamic coupling mechanism. This mechanism drove repeated switches of the regional stress regime in South China between NW–SE-directed extension and compression. Through far-field transmission, the NW–SE stress field exerted persistent control on the tectonic evolution of the eastern Sichuan fold belt east of the Huaying Shan fault zone, significantly influencing the development of its fold-thrust systems.