Late Ordovician Conodonts and Brachiopods from near Greenvale in the Broken River Province, North Queensland

Abstract

Late Ordovician conodonts and brachiopods are described from limestones (previously referred to the Carriers Well Formation) in the Wairuna Formation of the Broken River Province. The conodonts include the new genus and species Molloydenticulus bicostatus. Scabbardella altipes, Besselodus fusus sp. nov. and Protopanderodus liripipus dominate the conodont fauna of 24 species, which is typical of the Protopanderodus biofacies, with two large, robust species of Protopanderodus making up about one-quarter of recovered elements. Associated lingulate brachiopods include species of Acrosaccus, Atansoria, Biernatia, Conotreta, Elliptoglossa, Hisingerella, Nushbiella, Paterula and Scaphelasma, identical with those known from the Malongulli Formation and correlative units of the Macquarie Volcanic Province in central New South Wales. Many of the same conodont species found in allochthonous limestones in the basal Malongulli Formation also occur in the fauna from north Queensland, supporting its assignment to the Taoqupognathus tumidus–Protopanderodus insculptus conodont Biozone of late Eastonian age, equivalent to the middle Katian Stage. Subtle palaeoecological differences between the fauna of the deeper water Malongulli Formation limestones and that from the Broken River Province limestones indicate that the latter were likely originally deposited on or near the shelf edge. Recognition of this unstable depositional environment confirms interpretation of these limestones as allochthonous, having been reworked into younger basinal sediments of the Wairuna Formation.