Late Jurassic volcano-sedimentary sequences, filling process and evolution of basins in the Chengde area, Yanshan tectonic belt, China

The Upper Jurassic in the Yanshan belt consists of the Tiaojishan and Tuchengzi formations. Analysis of the radiometric age data of the volcanic rocks indicates that the main parts of the two formations formed synchronously, rather than show a simple overlapping stratigraphic relation. Based on an analysis of the lithofacies, facies association, direction of paleocurrents and provenance, the Late Jurassic sedimentary environment in the Chengde area has been reconstructed, and it is thought that the sediments in the basins in the early stage of its development mainly came from north of the basin. However, even so, the authors do not think that the basin development was controlled by a south-vergent thrust fault in the north. The Sbangyi-Pingquan fault has pronounced strike-sfip features and controlled volcanic eruption. The paper proposes a new model for the basin evolution in the Chengde area, which may well explain the development of volcano-sedimentary sequences, changes in direction of paleocurrents and provenance and tectonic-sedimentary process of basins in the Chengde area.