Late Jurassic-Early Cretaceous Deformation in the Western Yanshan Fold-Thrust Belt: Insights From Syntectonic Sedimentation in the Chicheng Basin, North China

摘要

The Yanshan fold-thrust belt is a significant intraplate deformation belt along the northern margin of North China Craton and records multiple phases of deformation during the Mesozoic. However, the specific tectonic evolution of the Yanshan belt during the Mesozoic has long been debated. In particular, many arguments exit regarding whether a contractional or extensional context dominated the Yanshan belt in the Late Jurassic-Early Cretaceous. One reason for this argument is the poor understanding of the tectono-sedimentary relationship preserved in the sedimentary records. A lack of evidence of syntectonic sediments makes it more difficult to reconstruct this relationship. The Chicheng basin in the western Yanshan belt contains complete Upper Jurassic-Lower Cretaceous succession and is bounded by marginal faults. New regional geological mapping, detailed sedimentary facies analysis, and recognition of two growth strata packages help reconstruct the tectono-sedimentary relationship in the Chicheng basin. Additionally, zircon U-Pb dating provides constraints on the timing of the deformation. Our results suggest that the dynamic sediment dispersal system in the Chicheng basin during the Late Jurassic-Early Cretaceous were controlled by two phases of thrusting, including the activities of the Shangyi-Pingquan fault during 162-147 Ma, and the Fengning-Longhua fault during 140-135 Ma. Therefore, we propose that the western Yanshan belt was in a contractional context during the Late Jurassic-Early Cretaceous. Our findings indicate that the tectonic setting of the Yanshan belt experienced a prominent transition from E-W trending structures to NE-SW trending structures and that this transition was probably related to subduction of the Paleo-Pacific plate beneath the East Asian continent.