Paleoenvironmental reconstruction, sequence stratigraphy and diagenetic processes of the Asmari Formation in KabirKuh Anticline, North of the Zargos Basin, Iran

摘要

Because of the importance of the Asmari Formation in Lurestan zone (north of the Zagros basin), Jahangirabad section with a total thickness of 179 meters consist of mixed limestone-evaporites have been studied in order to interpretfacies, paleoenvironment, sequence stratigraphy and diagenetic processes. Based on lithostratigraphic classification in Lurestan zone by Adams studies, the Asmari Formation (Late Oligocene - early Miocene deposits) in study area has been divided into 3 units (including 5 sub-units). According to the field studies and laboratory works, 13 microfacies in 5 facies association were recognized, which belong to open marine, shoal, lagoon, intertidal environments. By considering the Lower Kalhur evaporites (with observed micro-texture), which are located in the lower part of this formation, it seems that the precipitation of these evaporates has occurred in the restricted basin during fall of sea level in saline environments. The precipitation of limestone with pelagic fauna has occurred over basal anhydrite during the rise of sea level. The main recognized diagenetic processes are dissolution and dolomitization which has influence on Asmari formation in this region. Three depositional sequences were identified based on facies distribution and sequence boundary.