Paleomagnetism of Cretaceous rocks in the Jiaodong Peninsula, eastern China: Insight into block rotations and neotectonic deformation in eastern Asia

Although first‐order agreement of paleomagnetic directions between south China and Siberia shows that terranes between them were sutured by Cretaceous times, deformation by ongoing tectonism has continued and been especially focused near the continental margin of eastern Asia. To help evaluate differential rotations and relate them to regional strike‐slip and extensional tectonic regimes, we have conducted paleomagnetic study on Cretaceous sediments and volcanic rocks from the Jiaodong Peninsula south of the Bohai Sea in eastern China bordering the Tan‐Lu Fold Zone (TLFZ). Paleomagnetic results from 73 sites in the (Early Cretaceous) Laiyang and Qingshan groups and (Late Cretaceous) Wangshi Group yield magnetizations of primary or synfolding (mid‐Cretaceous) origins. Large differential block rotations of Early Cretaceous age are identified near the Muping‐Jimo Fracture Zone (MJFZ) dissecting the peninsula although Late Cretaceous declinations are regionally systematic and show post‐Late Cretaceous counterclockwise rotation of ∼14° in the Jiaolai Basin relative to the reference North and South China blocks. Block boundaries are identified as the TLFZ to the west and the MJFZ in the southeast. The eastern Jiaodong Peninsula is rotated clockwise relative to the North and South China blocks by a comparable amount (∼20°) to the southern Korean Peninsula to the east and to the Liaodong Peninsula and Yanji Basin to the north. Although these blocks are unlikely to be tightly coupled, their collective clockwise rotation mirrors counterclockwise rotations north of the Japan Sea and probably resulted from regional extension focused above uprise of asthenosphere beneath eastern Asia during Cretaceous times.