A modern assessment of Ordovician chitinozoans from the Shelve and Caradoc areas, Shropshire, and their significance for correlation

Abstract

AbstractNew chitinozoan data are presented from the classical section along the Onny River in the type Caradoc area, and from the deeper-water sections in the Shelve area, including the former British candidate GSSP for the base of the Upper Ordovician Series. The rich and well-preserved chitinozoan fauna of the Onny River has been a standard for 40 years, but new data revise some of the identifications. The assemblages are now attributed to biozones that are more readily applicable for international correlation. The main part of the section can be interpreted as belonging to the originally BaltoscandianSpinachitina cervicornisBiozone, although this is uncertain in the lower part. Within this biozone, theFungochitina actonicaSubzone has been defined. The Onny Formation at the top of the section is equated with theAcanthochitina latebrosa–Ancyrochitina onniensisBiozone; contrary to earlier reports,Acanthochitina barbatais absent. The Lower Wood Brook and Spy Wood Brook section from the Shelve Inlier yielded a great number of moderately to well-preserved chitinozoans, but a low-diversity assemblage. Their ranges have been neatly positioned against the well-known graptolite stratigraphy in the area. A localEisenackitina rhenanaBiozone? has been recognized, allowing us to suggest some international correlations.