Late Jurassic basin-fill record and its implication for basinmargin tectonism, Chengde, Yanshan Mountains, North China

The Late Jurassic Luanping-Chengde and Dazhangzi-Xinchengzi basins are linked with Fengning-Longhua and Shangyi-Pingquan thrust belts, respectively. The basin-fill of the Tuchengzi Formation is vertically divided into three basin-phases, which consist of braided channel plain and braided channel delta depositional systems. The statistics of the components of the sediment lithic fragments and gravels shows that there are three vertical cycles of metamorphite lithic fragment increase upwards in the northern Luanping-Chengde Basin, and three vertical cycles of carbonate and clasolite lithic fragment increase upwards in the southern Luanping-Chengde Basin and Dazhangzi-Xinchengzi Basin. Several conclusions have been made from basin sedimentology study. The southern and northern margins of the Luanping-Chengde Basin were controlled by the northern Shangyi-Pingquan thrust faults and Fengning-Longhua thrust faults, respectively, and the Dazhangzi-Xinchengzi Basin controlled by the southern Shangyi-Pingquan thrust fault. If a long distance thrust happened along the Chengde fault, the thrust might have not occurred at the syn-depositional stage of the Tuchengzi Formation or later, but should have occurred after the Tiaojishan Formation and before the Tuchengzi Formation. The three lithic petrofacies cycles and basin phases in the basins represent three uplift and unroofing processes along the basin marginal thrust belts.