The study of ichnofabrics, depositional environment and paleoenvironment of the Guri Member (Mishan) Formation in the stratigraphy sections of Chahar bisheh, Aghajari and Parsi oil fields, SW Iran

 The Miocene Guri member is characterized as one of the most significant successions in the Zagros basin. The Guri member is composed of carbonate (Limestone and marly limestone) and Marl (calcareous Marl) layers with abundant imperforate and perforate benthic foraminifera. The paleoenvironmental analysis, facies, depositional environment and diagenetic proceses of the Guri Member of Mishan Formation are described from three stratigraphic sections (Milaton, Omidieh and Shahid rajaei) in the Chahar bisheh, Aghajari and Parsi oil fields, south west iran. The petrographic analysis of the Guri member led us to identify 11 microfacies that are belonged to shoal, lagoon, and tidal flat environments. These microfacies deposited on a shallow carbonate ramp (homoclinal ramp) with the gentle slope. Bioturbation, micritization, cementation, neomorphism, physical and chemical compaction, dissolution, replacement and fracturing are the main diagenetic features that are created in the marine, meteoric, burial and uplift diagenetic environments. The sediments of the Guri Member are dominated by Thalassinoides suevicus in the Y, T, question mark and cylindrical shaped burrows. These trace fossils created by the Miocen crabs. The bioturbations in the layers are categorized into five ichnofabric classes which are equal to standard ichnofabric indexes of 1 to 5. The more ichonfabrics in the Omidieh section than in Parsi has been due to the large changes in environmental conditions such as depth, salinity and oxidation rate. Paleoenvironmental investigations of Thalassinoides suevicus indicates a very shallow, warm marine conditions with very high oxygen rate.