Late Ordovician faunas from the Quandialla-Marsden district, south-central New South Wales

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Abstract

Two Late Ordovician faunas, one from shallow water limestones and the other from deep water spiculitic siltstones, are documented from the southern Macquarie Arc in south-central New South Wales. Limestone encountered in the subsurface during exploration drilling in the Barmedman Creek area (midway between Marsden and West Wyalong) yields Eastonian conodonts including Aphelognathus cf. webbyi, Belodina compressa, Phragmodus undatus, Tasmanognathus cf. borealis and Yaoxianognathus? Tunguskaensis. Associated macrofauna includes the corals Tetradium tenue, Bajgolia? cf. grandis, Propora bowanensis, Paleofavosites?, Cystihalysites, Halysites and Palaeophyllum, stromatoporoids Labechiella variabilis, Stratodictyon ozakii, Clathrodictyon cf. microundulatum and Ecclimadictyon, and sponge Cliefdenella cf. perdentata. The Jingerangle Formation, exposed between Caragabal and Quandialla, may be as young as Bolindian 2 on the basis of some poorly preserved graptolites. Associated nektic nautiloids and sponges (Hindia) represent components of Benthic Assemblage 4-5, suggesting a deep water environment. The limestones at Barmedman Creek, and the spiculitic clastic rocks of the Jingerangle Formation, are associated (although exact relationships are unclear) with two separate volcanic complexes in the Macquarie Arc. Late Ordovician successions exposed further north in the area west of Parkes and Forbes, where early to late Eastonian limestones are overlain by early Bolindian deep water sediments, provide the closest regional analogues to the fossiliferous strata documented in the paper.