The biotic crisis of end-Guadalupian in the Hambast Valley section, Abadeh, southwest Iran and its comparison with coeval deposits in eastern Tethys

The study of Faunal biodiversity distribution in the strata close to the Middle and Upper Permian boundary in the Hambast Valley section was carried out. Considering obvious environmental and faunal changes in the topmost horizon of the subunit 4a of the Abadeh Formation, the end-Guadalupian extinction has happened before Guadalupian–Lopingian boundary. The significant changes near the Guadalupian-Lopingian boundary in this section are the presence of dolomite and stromatolitic limestone at the topmost part of the subunit 4a, implying the shallowness of the depositional environment as well as the noticeable decline of faunal biodiversity. The cause of end-Guadalupian bio-crisis in the Hambast Valley section is more likely due to the falling sea level. The examination of the end-Guadalupian extinction horizon in South China and Japan shows its position at the end of Capitanian. In South China (Penglaitan section) and Abadeh (Hambast Valley section), the end-Guadalupian eustatic regression has only left shallowing effects with environmental and faunal changes implying the end-Guadalupian extinction evidence. In the Hambast Valley section, the latest Capitanian Hemigordius irregulariformis Zone with some Codonofusiella species in the basal part of the subunit 4b are representative of the re-occurrence of the foraminiferal fauna after the end-Guadalupian extinction, while fusulinid Zone of early Wuchiapingian Codonofusiella-Reichelina is indicative of post-extinction foraminiferal recovery.