Depositional Evolution and Bio-Geochemical Changes across the Permian–Triassic Transition in the central Persian Gulf

Articles in Press

Document Type : Research Paper

Authors

1 Geological Survey and Mining Exploration Organization, Southern Branch (Shiraz)

2 Uinversity of Kharazmi, Tehran, Iran

3 Faculty of Geology, College of Sciences, University of Tehran

Abstract

In this study, the stratigraphic distribution of foraminifera and the environmental evolution of the Permian–Triassic boundary successions in the central Persian Gulf (upper Dalan Member and the basal part of the Kangan Formation) were investigated through the integration of micropaleontological, microfacies, and isotopic analyses (δ¹³C, δ¹⁸O, and ⁸⁷Sr/⁸⁶Sr). The results reveal three local composite biozones within the upper Dalan and lower Kangan units, along with the abundance of the index taxon Paradagmarita, which shows biogeographic affinity with approximately coeval strata in Turkey, the Caucasus, Saudi Arabia, and Oman. Microfacies analysis identified three facies belts—lagoonal, subtidal shoal, and tidal flat—indicating a general shallowing trend from lagoonal toward peritidal settings. A simultaneous decrease in δ¹³C and δ¹⁸O values was observed near the boundary, coinciding with the biotic crisis and the development of oxygen-depleted conditions. The increase in ⁸⁷Sr/⁸⁶Sr ratios across the boundary suggests enhanced influx of continental materials and intensified chemical weathering. The results also indicate a moderate increase in ooid size and significant changes in foraminiferal assemblages, reflecting a relatively shallow, warm, stressed, and oxygen-deficient environment. The novelty of this study lies in the combined application of three independent datasets—sedimentological, geochemical, and paleontological—from multiple subsurface sections, enabling a more precise reconstruction of the environmental evolution and biotic events at the onset of the Triassic.

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Journal of Stratigraphy and Sedimentology Researches

Articles in Press, Accepted Manuscript
Available Online from 01 November 2025

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