Sedimentary environment of Tarbur Formation in the Interior Fars Province, Mandeng and Khanehnahar sections

In this study, two stratigraphic sections of the Tarbur Formation have been investigated in the Structural Zagros Fold-Thrust Belt. The Tarbur Formation in the studied area conformably underlaid the Gurpi Formation but its top boundary overlaid by Bakhtiyari and Sachun formations as a disconformity. Due to the abundance of fossil content in these sediments, most of the studies had been focused on paleontology aspects. Lithological and facies studies on the sediments of this formation in the Interior Fars Province show the existence of 12 carbonate sedimentary facies in these sediments, which are scattered in four sub-environments including open marine, bioclastic shoal, lagoon and tidal flat. The abundance of benthic foraminifera in these sediments shows the change of conditions from deep to shallow environments. The results of field investigations and the trend of lateral and vertical changes of facies and sub-environments reflect the presence of a homoclinal carbonate ramp during the deposition of these sediments. The trend of changes in the depth of the facies, their distribution pattern and the characteristics of the upper boundary of the formation in the studied sections show that the Mandegan section was located in the shallow part of this ramp and there was a deepening trend in the environment towards the south-east towards the Khanehnahr section. In addition, the replacement of large benthic foraminifers by bivalves such as rudist is another confirmation of the decreasing depth trend over time. These results can be used in reconstructing the evolution of the sedimentary basin in this region.