Biostratigraphy and paleoecology of non-marine ostracods from the Cretaceous deposits in southwestern Korean Peninsula: a preliminary report

This study presents the first investigation (taxonomy, biostratigraphy and paleoecology) of non-marine ostracod faunas from three small Cretaceous deposits of the Dalido Formation, Sunchang Trough, and Anpo Tuff in southwestern Korean Peninsula (Jeollanam-do Province). The biostratigraphic interpretations based on five ostracod species in the studied areas are as follows. (1) Dalido Formation (Aphaedo Island, Sinan): Only one species (Mongolocypris sp.) with few specimens is discovered. However, the record of the Genus Mongolocypris and the previous age dating results may indicate that this formation was formed in the Albian or possibly up to the Cenomanian; (2) Sunchang Trough (Jangseong area): Three representatives of the Family Cyprideidae (Cypridea cf. barsboldi, C. sp., and Mongolocypris distributa) are identified, and two of them are very similar to ostracods from the Upper Cretaceous deposits of China and Mongolia. Thus, the stratigraphic age of sediments of the Sunchang Trough is presumed the Campanian in age, as the previous age data; (3) Anpo Tuff (Nangdo Island, Yeosu): Mongolocypris distributa and Candona sp. of this deposit show affinities to the Late Cretaceous faunas (Campanian to Maastrichtian) of other East Asian regions. Thus, the ostracod faunas in the studied areas can be divided into two assemblages: the 'Mid'-Cretaceous ostracod assemblage for the Dalido Formation, and the Late Cretaceous ostracod assemblage for the Sunchang Trough and Anpo Tuff. The low-diversity with the dominance of cypridoideans in each studied area is indicative of the unstable/ephemeral waterbodies and/or result of less faunal exchanges between other East Asian regions and southwestern Korean Peninsula. Although many fossils show bad preservation, ostracod species should improve further understanding of biostratigraphic and paleoecological implications of the Cretaceous deposits in southwestern Korean Peninsula.