Artinskian (early Permian) Foraminiferal Assemblages from the Western South Qiangtang Block, Tibet: Implications for Taxonomy, Biostratigraphy, and Paleobiogeography 38

The South Qiangtang Block is one of the key blocks within the Cimmerian continent, which underwent significant paleogeographic changes and climatic amelioration after the Late Paleozoic glaciation. The faunas from this block preserve important records of paleogeographic and paleoclimatic information. Recently, we investigated the Permian sequence in the western part of the South Qiangtang Block. This sequence is characterized by a transition from glaciomarine diamictites of the Cameng and Zhanjin formations to shallow marine deposits of the Qudi and Tunlonggongba formations. We recently studied the foraminifers from the Tunlonggongba Formation in three stratigraphic sections (Domar-2014, Domar-2015, and Tuotala-2017) in the Domar area. Our study identified 40 species belonging to 25 genera and 15 families of fusulines and smaller foraminifers, including three new species: Pseudofusulina qiangtangensis n. sp., Hemigordius nagriensis n. sp., and Uralogordiopsis domarensis n. sp. Based on their stratigraphic distribution, we established one fusulinid Pamirina Zone and three smaller foraminiferal assemblages, namely Hemigordius–Rectogordius Assemblage, Uralogordiopsis–Nodosinelloides Assemblage, and Hemigordius–Uralogordiopsis Assemblage. The occurrence of the fusulines Pamirina and Pseudoreichelina suggests an Artinskian age for this formation, rather than the previously proposed Kungurian age. Furthermore, the presence of these zonal genera in the South Qiangtang Block indicates strong faunal affinities with coeval Tethyan and Panthalassan regions, implying the invasion of warm-water faunas from these areas. Considering the lithological transition from glaciomarine deposits to carbonate deposits, coupled with the advent of warm-water faunas, this phenomenon is interpreted as the result of the Artinskian warming event following the Late Paleozoic glaciation. It should be noted that such Artinskian fusulines and smaller foraminifers are completely absent from the Lhasa Block and the Tethys Himalaya area to the south. Therefore, the northward drift of the South Qiangtang Block is also invoked to explain the paleobiogeographic differences between the South Qiangtang Block and the adjacent blocks to the south. Consequently, both paleogeographic and paleoclimatic factors are acting on the faunas from the South Qiangtang Block.