Late Ordovician Conodonts and Macrofossils from Subsurface Carbonates near Quandialla and Inferred Depositional Age of the Currumburrama Volcanics in South-Central New South Wales

Abstract

Late Ordovician conodonts and macrofossils (corals, calcareous algae and bryozoans) were recovered from an unnamed limestone unit within the Currumburrama Volcanics, intersected in drill hole CBMD006 located in the vicinity of Quandialla and Caragabal in south-central New South Wales. The conodont assemblage from the lower part of the limestone unit is characterized by moderately common  Belodina compressa  elements and is assigned to the B. compressa  Biozone of late Sandbian age, consistent with corals from the upper part of the limestone which suggest a latest Sandbian to earliest Katian age. These fossils support direct correlation with an unnamed carbonate unit within the Lake Cowal Volcanic Complex previously reported near Marsden, about 18 km to the WNW. Together these palaeontological and biostratigraphic studies provide crucial age constraints for the Upper Ordovician volcanic sequences distributed in the southern Junee–Narromine Volcanic Belt (JNVB). Furthermore, they underpin precise correlation with the well-dated marine shelf successions and associated volcanic sequences exposed in the central and northern part of the JNVB, within the Ordovician Macquarie Volcanic Province in central New South Wales.