The paleodepositional environment, diagenetic and depositional conditions of the Middle-Late Miocene Koluz gypsum member (NE Van, Eastern Turkey)

Abstract

This study investigates the depositional setting and diagenetic processes of gypsiferous sediments known as the Koluz gypsum member located in the northeast of Van (Eastern Anatolia-Turkey). The commencement of still-active contractional regime due to the collision of Eurasian and Arabian plates gave way to uplift events on the active Eurasian margin. This uplift initially resulted in termination of marine sedimentation and commencement of continental deposition in the region. The Middle-Late Miocene Kurtdeligi formation is one of the oldest products of the continental setting in the Eastern Anatolia. Sedimentologic and petrographic analyses conducted on the Koluz gypsum member of the formation, the main concern of this study, indicate that the member is represented by secondary gypsum (massive, laminated, nodular, satin spar) and primary gypsum lithofacies (selenite, gypsum arenite, discoidal and radial). The secondary gypsum facies are formed after hydration of anhydrite and anhydritizated primary gypsums. Additionally, mineralogical and geochemical studies suggest that carbonate (dolomite and calcite) and detrital materials found within the member formed during the deposition or late diagenetic processes. The high major and trace element values determined by XRF analyses also indicate intense detrital influx and accordingly terrestrial origin for the basin. Sedimentary textures and lithofacies of the member show a typical ephemeral playa complex, which was likely fed by both evaporation and groundwater discharge. Tectonism, climate, salinity variation, biologic activity and diagenetic and hydrothermal fluids play major roles in the formation and transformation of these sediments to each other.