Lopingian biotic crisis and global correlation: Evidence from the Abadeh section, central Iran

The Iranian tectonic blocks host well-preserved marine carbonate-dominated Lopingian (Upper Permian) strata, which have been proposed as one of the best international references for the Lopingian in the Tethyan Realm. However, the correlation of the Lopingian between Iran and other regions remains unresolved. The Abadeh section in central Iran is one of the most intensively studied Lopingian sections, yielding abundant conodonts, but with controversial taxonomy. This study presents an updated high-resolution Lopingian conodont succession from the Abadeh section. Fourteen conodont zones have been identified from the middle Abadeh Formation to the basal Elikah Formation, which can be well correlated with conodont successions from South China. Based on the lowest occurrences (LO) of Clarkina at the base of Unit 5 at the Abadeh section, the Guadalupian-Lopingian boundary (GLB) is within Unit 4b, much lower than that previously documented. The Wuchiapingian-Changhsingian boundary (WCB) is precisely constrained at 4.9 m below the top of the Hambast Formation. The Permian-Triassic boundary (PTB) is precisely constrained at 0.8 m above the base of the Elikah Formation. In addition, fusuline, ammonoid, and brachiopod biostratigraphy, as well as delta 13Ccarb, delta 18O, and Sr isotope chemostratigraphy, and magnetostratigraphy of the Abadeh section, are reviewed. As a result, here an integrative multidisciplinary timescale for the Abadeh section has been established. This timescale provides a state-of-the-art temporal framework for both the regional and global correlation of the Lopingian. The integrative fossil ranges at the Abadeh section indicate that the hypothesized end-Guadalupian mass extinction displayed a gradually decline until the middle Wuchiapingian, suggesting a model of protracted ecological turnover rather than a distinct mass extinction event. Whereas, although most of the fossil ranges disappeared before the Changhsingian, the pattern of the end-Permian mass extinction at Abadeh is consistent with all other regions.