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

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.

KEYWORDS:

• Microfossil collection
• Cypridoidea
• Late Cretaceous
• Hayang Group
• palaeoecology

Acknowledgments

We would like to thank Director Hang-Jae Lee, Dr. Seung-bae Lee and Dr. Paul S. Hong for permitting our inspection of the ostracod specimens in the microfossil collections of the Geological Museum, KIGAM. Mr. Jongyun Jung (Chonnam National University) is also thanked for drawing a geological map. We are very grateful to Dr. Renate Matzke-Karasz and an anonymous reviewer for their constructive comments.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This study was supported by the National Research Foundation of Korea (NRF), grant funded by the Korean government (Ministry of Science and ICT) [Grant No. RS-2023-00210214] for BDC, and National Natural Science Foundation of China [Grant No. 42372022] for YQW.