MESOZOIC TECTONIC STRESS FIELD IN THE YANSHAN MOUNTAIN REGION, WEST OF BEIJING

The present landscape of the Yanshan mountainous region was sculptured from rocks that had been formed and deformed during the past long geologic period of time.The region, as characterized by the sedimentary formations and structures had undergone rather weak tectonic movement from middle-late Proterozic to Paleozoic, represented by the dominating role of the basement faults. The major orogeny occurred here in the Mesozoic and Cenozoic, during which the rocks were strongly compressed to form linear folds and nappes.In this paper, emphasis is placed on the reconstruction of the Mesozoic stress field and deflection field of the region so as to restore the mechanics process and the movement leading to the deformation in Mesozoic and Cenozoic times.