Permian bivalves from West Spitsbergen, Svalbard Islands, Norway

Abstract

The bivalve fossils collected by Japanese-Norwegian research groups from the Kapp Starostin Formation in west Spitsbergen are described. They comprise fourteen species belonging to the Pterioida and two species of the Arcoida. Among them, six species, including two that are indeterminate, are newly described. They are Grammatodon (Cosmetodon)? suzukii, G. (C.)? sp. ind., Streblochondria winsnesi, Vorkutopecten svalbardensis, Deltopecten sp. ind., and Palaeolima nakamurai. The fauna belongs to the Boreal bioprovince, but a single species, Cassianoides sexcostatus (Stuckenberg) has also been reported from the Central Rocky Mountains of the United States. The bivalve fauna suggests an Artinskian-Kungurian age for the Kapp Starostin Formation. This is somewhat earlier than the age deduced from brachiopods and bryozoans, but it is not decisive because the materials are poor. The Kapp Starostin Formation is conformably overlain by the Otoceras-bearing, earliest Triassic Vardebukta Formation, so a time-gap corresponding at least to the Dorashamian and Dzhulfian (=Tatarian) is inferred between the two formations.