Effect of regional and global events on the diversity of Permian Foraminifera in Central Alborz, Western Tethys

A relatively complete succession of Permian in Central Alborz was studied from aspects of lithostratigraphy, biostratigraphy, petro and microfacies analyzing and estimation of foraminifera diversity to investigation of changes in foraminifera diversity and it’s relation to global and regional events. The first studied section of the Permian succession was the type section of the Dorud Formation, located at north of the Dorud village and the second outcrop which has been studied for Middle Permian ( Ruteh Formation) and Upper Permian (Nessen Formation) is located NW of Heev town - SE of Gazvin . Biostratigraphy was done based on lithostratigraphy and extension of taxa. We separated Permian stages (Asselian to Dzhulfian) by using index nonfusulinid assemblages. To reconstruction of sedimentary environment we consider petrofacies, microfacies and field evidences of rock unites. Analyzing of facies was done and then we reconstructed sedimentary environment and draw relative sea level changes. To investigation of foraminifer’s diversity we considered results of estimating stand diversity and increase the maximum amount of diversity up to 100 and calculate other amounts and then draw spindle diagram of diversity. The event stratigraphy of Permian prepared by incorporation of several studies in global and regional scale; Muttoni et al., 2009; Isozaki, 2009; Isozaki, 1997; Heydari et al., 2013. Results showed a constant increasing in diversity amount from Asselian to Murgabian with the exception of late Yakhtashian. The highest diversity of foraminifera is seen in the Murgabian that is comparable with Kamura high Ca productivity. The main decrease in diversity happened during the Midian which corresponds to the Kamura cooling event. Depositional environment and relative sea level changes resulted from analyses of petrofacies and microfacies of Dorud, Ruteh and Nessen Formations showed three main rises and two falls in sea level, comparable with global sea level changes and regional Tethian geological main events such as Neo-Tethys opening and Cimmerian terranes migration to subequatorial paleolatitude position. Incorporation of the results provides concordance between foraminifer’s paleobiodiversity, environmental condition, relative sea level changes and main global and regional events.