Ostracods from the non-marine Lower Cretaceous interval at Liying section of Luanping Basin, North China: A stratigraphic correlation

Non-marine strata of Lower Cretaceous age in western Liaoning and northern Hebei, North China, are famous for its Jehol Biota, including abundant ostracods. However, there are still some controversies about the stratigraphic correlation in these regions, for instance, it is still debated whether the interval from the Liying section of Luanping Basin belongs to the Dadianzi Formation or the member 1 of the Xiguayuan Formation. Ostracods act as an important tool for the correlation of the stratigraphy within or between basins. Here we report and illustrate the ostracods from the Liying section in detail for the first time, and aim to determine the section's stratigraphic correlation. Results show that, the Liying section has a thickness of 157.65 m and can be divided into 33 layers. Ostracods from this section are mainly distributed in the lower and middle part, and 7 genera and 13 species have been preliminarily recognized. These ostracod species can be summarized as the Cypridea-Limnocypridea-Lycopterocypris Assemblage Zone temporarily. Based on the identified ostracods, occurrence of other abundant representative fossils of the Jehol Biota, and isotope dating results, the major interval of the Liying section should be assigned to member 1 of the Xiguayuan Formation, and can be correlated with the Yixian Formation from western Liaoning.