New discovery of Ordovician conodonts from Beijing and their stratigraphic significance

This paper reports a taxonomic and biostratigraphic study of conodonts recovered from the Bei’anzhuang Formation in the K20 borehole of the Beijing area. Seven carbonate core samples were obtained and acid-leached, from which forty-six conodont elements were obtained. These are assigned to eight species of seven genera and an additional form that cannot be positively identified. The conodont fauna is composed of Tangshanodus tangshanensis An, 1983, Tangshanodus cf. tangshanensis An, 1983, Drepanoistodus pitjanti Cooper, 1981, Histiodella holodentata Ethington and Clark, 1981, Panderodus nogamii (Lee, 1975), Erraticodon tangshanensis Yang and Xu in An et al, 1983, Rhipidognathus laiwuensis Zhang in An et al., 1983 and Triangulodus changshanensis Zhang in An et al., 1983. It is attributed to the Histiodella holodentata–Tangshanodus tangshanensis Biozone, characteristic of the upper part of the Bei’anzhuang Formation (middle Darriwilian, DW2 Stage Slice). The Histiodella-bearing conodont fauna is dominated by warm-water taxa, reflecting a typical North China affinity, and correlates well with other faunas worldwide. The material enriches the record of Ordovician conodont faunas in the North China region and advances our understanding of middle Darriwilian (Middle Ordovician) conodont biostratigraphy in Beijing and the broader North China region.