Two development stages of the Tanlu fault zone: the stages of the overthrust fault zone sensu lato and the wrench fault zone sensu stricto

Abstract：The Tanlu fault zone has experienced two main development stages since the Hercynian. The first stage was a stage of the development of the Tanlu fault zone sensu lato. In the Late Triassic-Early Jurassic, the collision between the Yangtze plate and North China plate gave rise to a boundary of the two plates, which was of overthrust nature, belonging to the Tethys tectonic domain sensu lato. In the second stage, since the Early Cretaceous, the fault has developed into a wrench fault zone, which belongs to the wrench system of the circum-Pacific tectonic domain sensu stricto. Lithofacies and paleogeography shows that the junction between the Yangtze plate and North China plate was initiated in the early Late Permian and that the Indosinian Tanlu fault zone was a gently “S”-shaped block amalgamation boundary of NE and NNE trends, which displays the nature of a residual NE- and NNE-trending, oblique overthrust zone in the present Tanlu fault zone, while the middle and lower tectonic layers show ductile overthust deformation and the upper tectonic layer shows the deformation inside a foreland fold-thrust zone. Stress field analysis indicates that: as early as the late Early Triassic nearly N-S compression occurred at shallow levels of the crust and sinistral strike-slip movement was initiated; in the late Early Cretaceous the fault zone began to turn into the extension stage, which was consistent with the extension in eastern China; and in the Neogene it underwent nearly E-W compression, resulting in thrusting and dextral strike-slip movement.