Late Visean–Early Gzhelian foraminifera in Hexi Corridor, China: geological implications

The Carboniferous strata are widely distributed in the Hexi Corridor, Northwest China, with a complete stratigraphic sequence and abundant fossils. Four stratigraphic sections of the Carboniferous in the Hexi Corridor were selected for this study, which mainly examined foraminiferal assemblages. Based on the distribution of the foraminifera throughout these sections, four foraminiferal assemblages were established. In the ascending order, these assemblages are the Eostaffella proikensis–Koskinobigenerina (Aleksian, Late Visean), Climacammina simplex–Biseriella parva (Venevsky, Late Visean), Ozawainella guizhouensis (Middle to Late Bashkirian), and Nodosinelloides spp. (Kasimovian–Early Gzhelian). Foraminifer data indicate the direction of regression in the late Visean in the studied area was from east to west. During the Late Visean–Early Gzhelian, a comparison of recovered fauna with the paleobiogeographical affinities shows that the Hexi Corridor foraminiferal fauna maintains strong North Paleotethyan affinities.