Paleoenvironment, Biostratigraphy and Sequence stratigraphic studies of the Permian-Triassic boundrary of the offshore Persian Gulf, Iran: using an integrated approach.

Four supergiant and numerous giant gasfields have been discovered in the Southwest Iran which produce from Permian-Triassic carbonates belong to the upper member of Dalan Formation and Kangan Formation. In this research a detailed biostratigraphic, microfacies and sequence stratigraphic study of the late Middle Permian to Triassic successions was undertaken from 850 thin sections prepared from cutting chips of well SPD12C-08 in South Pars Gas Field.Comparisons done with traditional Lopingian reference sections, allow sub-dividision of the Permian part into four main biozones: 1) The late Midian is characterized by the FAD and the LAD of Shanita amosi.2) The early Wuchiapingian is characterized by the FAD of Paraglobivalvulina mira.3) The “middle” Wuchiapingian is defined with the appearance of the Paradagmarita monodi and numerous regional markers.4) The late Wuchiapingian is characterized by the FAD of Charliella altineri and Spirorbis phlyctaenae.The Triassic strata were all included in Spirorbis phlyctaenae Zone. Comparing the differentiated biozones with Tethyan zonation an age of Late Midian-Late Djulfian and Anisian is confirmed for the Dalan-Kangan formations, respectively.Microfacies studies led to the identification of 11 microfacies related to five facies belts. Also four depositional sequences within several 3rd order cycles have been recognized.