Biostratigraphy, Microfacies and Depositional Environment of the Sarvak Formation at the Pyun Anticline (Zagros Basin, Southwest of Iran)

The Sarvak Formation is a carbonate sequence of Late Albian-Early Turonian age in Zagros Basin in Iran. In this investigation, the Sarvak Formation at the Pyun Anticline section (Izeh Zone) has been studied. It consists of 797 m thick limestone which overlies the Kazhdumi Formation conformably and underlies the Gurpi Formation unconformably at the Pyun Anticline. A very rich fossil association (85 genera and 132 species) characterizes the Pyun section. Based on the stratigraphic distribution of diagnosed foraminifera, five biozones are established: 1, Muricohedbergella-Globigerinelloides sp. assemblage zone (Late Albian); 2, Praealveolina iberica-Chrysalidina gradata interval zone (Early Cenomanian); 3, Chrysalidina gradata-Cisalveolina fraasi (fallax) and C. lehneri interval zone (Middle Cenomanian); 4, C. fraasi (fallax) and C. lehneri-Praetaberina bingistani assemblage zone (Late Cenomanian); 5, Nezzazatinella picardi-Mangashtia-Dicyclina assemblage zone (Early Turonian). Based on the petrographic and sedimentological analyses, some 13 carbonate microfacies were identified. The investigated microfacies confirm a ramp-type paleoenvironment. These microfacies, from distal to proximal environments, consist of: MF1: planktonic foraminifera wackestone-packstone; MF2: Oligostegina planktonic foraminifera wackestone to packstone; MF3: planktonic-benthic foraminifers sponge spicules wackestone-packstone; MF4: rudist floatstone; MF5: rudist rudstone; MF6: bioclast intraclast grainstone; MF7: peloid intraclast grainstone; MF8: benthic foraminifers rudist grainstone-packstone; MF9: peloid bioclast grainstone-packstone; MF10: bioclast (benthic foraminifers) wackestone-packstone; MF11: peloid bioclast packstone; MF12: dacycladacea benthic foraminifera packstone-wackestone; MF13: miliolids wackestone-packstone.

Automated summary

The study focused on the Sarvak Formation in the Zagros Basin of Iran, specifically at the Pyun Anticline section. A rich fossil assemblage and five biozones were identified, while 13 carbonate microfacies were also recognized based on petrographic and sedimentological analyses. The microfacies confirmed a ramp-type paleoenvironment.