Upper Ordovician conodonts from the Taoqupo section in the southwestern margin of the North China Craton

Abstract

A diverse but relatively low yielding conodont fauna has been recovered from the Yaoxian and the Taoqupo formations at the Taoqupo section, Tongchuan City, Shaanxi Province, North China. This conodont fauna comprises 20 species belonging to 12 genera, exhibiting a mixture of North China and North American Midcontinent provincial affinities, and with several pandemic species associated. Five stratigraphically important species are documented in detail. Among them, Tasmanognathus shichuanheensis is revised as having a septimembrate apparatus. Five successive conodont biozones of late Sandbian to middle Katian age are recognized, namely the Tasmanognathus shichuanheensis Biozone, the Phragmodus undatus Biozone, the Belodina confluens Biozone, the Yaoxianognathus neimengguensis Biozone, and the Yaoxianognathus yaoxianensis Biozone, in ascending order. Some age-diagnostic and widely distributed conodonts present within the Taoqupo conodont fauna greatly facilitate a precise local, regional and international correlation of the present biozonation with coeval representative successions in North China, Northwestern China, South China, and the North American Midcontinent. Biostratigraphic correlations enable ages at the stage slice-level of the middle Sa2, the middle Sa2 to early Ka1, the middle Ka1, the late Ka1 to earliest Ka2, and the middle Ka2 to be assigned to the aforementioned five conodont biozones respectively.