Ostracod faunas from the Dalazi and Tongfosi formations (Yanji Basin, northeast China): Biostratigraphic, palaeogeographic and palaeoecological implications

Abstract

This work provides a detailed taxonomic study of ostracod species from the Dalazi and Tongfosi formations of the Yanji Basin (Jilin Province, NE China). Fourteen species including one new species belonging to nine genera have been recovered: Scabriculocypris tonfosiensis, Scabriculocypris yanbianensis, Cypridea concinaformis, Mongolocypris yanjiensis, Mongolianella kyranbeki sp. nov., Lycopterocypris infantilis, Lycopterocypris sp., Yumenella toorojensis, Candona spp., Cyprois sp., Vlakomia ustinovskii and Vlakomia jilinensis. With the recovery of well-preserved specimens, the sieve pore, ontogeny and sexual dimorphism of Vlakomia jilinensis and Vlakomia ustinovskii are recognized for the first time. The ostracod biostratigraphic correlations suggest that the age of the Tongfosi Formation is Albian and may extend upwards into the Upper Cretaceous, and the Dalazi Formation is not older than the Albian, probably of early Late Cretaceous age. The ostracod faunas of the Tongfosi and Dalazi formations show affinities to faunas of Eastern Mongolia and South Korea, providing evidence of potential faunal exchanges between Northeastern China, Eastern Mongolia and South Korea during the Albian to early Late Cretaceous time. On the basis of their ostracod faunas, the Tongfosi and Dalazi formations represent a shallow-littoral lacustrine depositional environment that potentially included small ephemeral water bodies.