Depositional environment and sequence stratigraphy of the Oligo-Miocene Asmari Formation in SW Iran

The Asmari Formation, a thick carbonate succession of the Oligo-Miocene in Zagros Mountains (southwest Iran), has been studied to determine its microfacies, paleoenvironments and sedimentary sequences. Detailed petrographic analysis of the deposits led to the recognition of 10 microfacies types. In addition, five major depositional environments were identified in the Asmari Formation. These include tidal flat, shelf lagoon, shoal, slope and basin environmental settings and are interpreted as a carbonate platform developed in an open shelf situation but without effective barriers separating the platform from the open ocean. The Asmari carbonate succession consists of four, thick shallowing-upward sequences (third-order cycles). No major hiatuses were recognized between these cycles. Therefore, the contacts are interpreted as SB2 sequence boundary types. The Pabdeh Formation, the deeper marine facies equivalent of the Asmari Limestone is interpreted to be deposited in an outer slope-basin environment. The microfacies of the Pabdeh Formation shows similarities to the Asmari Formation.