VARIATIONS IN TECTONIC STYLES IN THE ZAGROS GEOSYNCLINE AND THEIR RELATION TO THE DIAPIRISM OF SALT IN SOUTHERN IRAN

Abstract

A study of the surface and subsurface geology of the Zagros mountain belt reveals that, from the viewpoint of tectonic fabrics and the cause of diastrophism, the Zagros geosyncline can be divided into NW and SE segments. The NW segment was formed by orogenic compression and the SE segment primarily by epeirogenic uplifts. Movements of Infra‐Cambrian (Hormuz) salt at the base of the sedimentary column in the SE Zagros contributed to the epeirogenesis. Faults in the SE Zagros are of a normal type, whereas in the NW Zagros they are dominantly thrust. Seismic data indicate that movement of salt is the cause of many of the earthquake shocks in the SE Zagros.Hydrocarbons in the SSE Zagros either escaped through fractures within exposed reservoirs or migrated while epeirogeny was proceeding to be trapped in the western flank of the Oman high in the extreme SE portion of the Zagros belt.