تحليل تنش ديرينه در خاور و جنوب خاوري تهران (سرخه حصار - خجير)

The Paleostress Analysis in the East and South East of Tehran (Sorkheh Hessar-Khodjir)

To analyze the paleostress in Sorkheh Hessar - Khodjir area, different shear - fault planes and the associated slickenside line- ations are measured. The stress tensor and the variation of the stress direction in the upper Triassic to Oligocene formations are discussed. Numerous shear data are determined from different locations in the study area and categorized into 16 sites according to the stratigraphic age. The main criteria used to identify the sense of slip are accretionary mineral steps, tectonic tool marks, polished and rough facets, and riedel shears. According to the inversion method which includes determination of the mean stress tensor orientation and sense of slip on numerous faults ,all data are classified based on tectonic events and the principal stress axes and corresponding compressional and extensional directions are calculated. Based on the derived results from the diagrams, it is suggested that a prominent NE- SW compressional stress direction, which is obvious in Mesozoic and the younger Cenozoic formations, caused the deformation of the Mesozoic strata after Mesozoic and was continuous in Tertiary (Oligocene). It seems that a younger N-S stress direction exists and has had effects on both older and younger formations. It is believed that it would be related to one of the last Alpine orogenic phases.