Alternation of back-arc extension and compression in an overriding plate: evidence from Cretaceous structures in the western Liaoning region, eastern China
The dynamic evolution in an overriding plate remains a controversial issue. Cretaceous structures in the western Liaoning (WL) region of the eastern North China Craton (NCC), an overriding plate bordering the Pacific Ocean, provide insights into the dynamic evolution related to Paleo-Pacific Plate subduction. We present structural and fault-slip data from the Jurassic–Cretaceous basins in the WL region, together with previously published isotopic ages, to constrain structural and stress field evolution during the Cretaceous. These data reveal four phases of deformation in the WL region: tectonic shortening (D 1 ) at 137–136 Ma, extension (D 2 ) during 136–97 Ma, another shortening (D 3 ) at the beginning of the Late Cretaceous, and relatively weak extension (D 4 ) during the Late Cretaceous. Inversions of the measured fault-slip data yield NW–SE compression during D 1 , NW–SE extension during D 2 , NNW–SSE compression during D 3, and N–S extension during D 4 . Deformation phases D 1 and D 3 correspond to shortening events B and C of the Yanshan Movement, whereas D 2 corresponds to the peak destruction of the NCC in a back-arc extensional setting. The structural evolution indicates that the back-arc extension (D 2 ) of the Early Cretaceous started immediately after the brief shortening event D 1 and ended with another shortening event D 3 . Subsequently, the back-arc region underwent weak extension (D 4 ) during the Late Cretaceous. A slab-driven model could account for the tectonic evolution in the eastern NCC. Periodic changes in the kinematics of the subducting Paleo-Pacific Plate are responsible for the alternation of the back-arc extension and compression in the overriding plate.