Geochemical signatures and chemostratigraphic framework for the Early-Middle Permian sedimentary successions of Alborz, Iran

Abstract

This research analyzes how the prevailing physicochemical conditions during the deposition of the carbonate intervals of the Ruteh Formation (Early-Middle Permian), in the Alborz, Iran, led to changes in water-column redox conditions. The significance of this study lies in providing unique insights into the oxic-anoxic variations in the Tethys Ocean during the detachment of the western Cimmerian microcontinent from Gondwana. The onset of interglacial periods and the opening of the Neo-Tethys in the Artinskian stage led to rising temperatures, oxic conditions, and a decrease in the enrichment factor and carbon isotope values. In contrast, the Kungurian oceans were suboxic to anoxic, as evidenced by positive carbon isotope values, high enrichment factor, positive Eu and Ce anomalies, and increased primary productivity. These geochemical changes are attributed to volcanic activities in the Early Kungurian, followed by the transgression of seawater during the opening of the Neo-Tethys and the movement of the Cimmerian microcontinent in the Late Kungurian. These factors played a crucial role in the development of oxygen-deficient basins and the upwelling processes. During the Roadian stage, oxic conditions once again dominated in the basin. The increase in temperature, coupled with the Cimmerian microcontinent’s movement towards equatorial latitudes, may have been a significant factor contributing to the decrease in carbon isotopic values, enrichment factor, and productivity proxies. The results obtained extend beyond previous studies, demonstrating that the deposition of the Ruteh Formation was closely linked to global events.