Non-marine ostracods from the Cretaceous Banyaweol and Geoncheonri formations (Gyeongsang Basin, Korea) in the collections of the Geological Museum, KIGAM: Taxonomy, biostratigraphy, palaeobiogeography and palaeoenvironment

Abstract

ABSTRACT The Geological Museum of the Korea Institute of Geoscience and Mineral Resources (KIGAM) houses a large collection of microfossils. From these collections, 14 species belonging to six genera of non-marine ostracods from the Banyaweol and Geoncheonri formations of the Gyeongsang Basin, South Korea are identified: Cypridea sp. 1, C. sp. 2, C. sp. 3, C. sp. 4, C. sp. 5, C? sp. 6, Lycopterocypris triangularis, L. cf. profunda, Candona declivis, C. sp. Cypria cf. elata, Djungarica sp. Ziziphocypris costata and Z. rugosa. The biostratigraphic correlation based on L. triangularis and C. declivis from the Cenomanian Banyaweol Formation suggests that these species appeared at a much earlier stage than the previous records from China. Ostracods of the Banyaweol Formation may represent a transitional fauna during the mid-Cretaceous faunal turnover in East Asia. However, L. cf. profunda and C. cf. elata suggest a Turonian – Santonian age (probably extend upwards into Campanian) for the Geoncheonri Formation. Many non-endemic species of both formations indicate that these faunas were linked with ostracod faunas of East Asia, providing evidence of active faunal exchanges and migration. The palaeoenvironments of both formations are interpreted as ephemeral waterbodies and unstable shallow-littoral zone of lakes based on faunal compositions.