PERMIAN BASINS IN THE CENTRAL/EASTERN IRAN: STRATIGRAPHY, BIOSTRATIGRAPHY, GEOCHEMISTRY, PALEOENVIRONMENTAL SETTINGS

Permian marine sediments are widely distributed in Central/Eastern Iran. Several studies of these sediments have been accomplished in the past. However these studies were focused on different aspects of regional stratigraphy, biostratigraphy, regional geology etc. In the current project we are attempting to study Permian sediments as a combined effort on stratigraphy, sedimentology, biostratigraphy and geochemistry. The main aim of this study is better understand the geologic history of Central/Eastern Iran in Permian Period. The Permian sediments in the Central/Eastern Iran are known as two geographically separated Formations: Jamal and Khan. They were measured and described at 1:100 scale in 9 stratigraphic section. Petrographic thin-sections for microfacial analysis were obtained every 3-4 meters in average within the sections. Fusulinids, brachiopods and rugose corals were collected for biostratigraphy control. Advanced geochemical study has been performed in this project. O¹⁸ and C¹³ isotopes were utilized for better understanding of paleoenvironmental processes. Ca, Mg, Mn, Na, Sr and Fe amounts and ratios were used to compliment the isotopic study. Two different basins are recognized within studied area. The first basin, that we are proposing to call Jamal Basin, is entirely carbonate sedimentation, whereas the second - Khan Basin - formed under significant influence of siliciclastic input. Three environmental settings are recognized within the Jamal Basin: (a) very shallow carbonate platform with predominantly very shallow limestone sequences; (b) mid-ramp setting with relatively deep to shallow sediments (cherty limestone to wackstone/packstone, rarely fine grainstone); (c) slope setting with micritic limestone and deep water floatstones. Khan Basin is represented by cyclic sequences of relatively thin very shallow limestone and thick quarts gravel conglomerate and coarse sandstone, sometimes of continental origin. Character of sedimentation in Khan Basin suggests the presence of significant unconformities at the base of each siliciclastic unit. Sedimentation in the Khan Basin most likely ended before the Late Permian (Lopingian).