Conodont Biostratigraphy of Ordovician Deep-Water Turbiditic Sequences in Eastern Australia—A New Biozonal Scheme for the Open-Sea Realm

Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples (>3 000 thin sections) from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales, Australia. Based on these faunas, a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones. They are (in ascending order) the Paracordylodus gracilis Superbiozone (including the Prioniodus oepiki Biozone), Periodon flabellum Superbiozone (including the Oepikodus evae Biozone in the lower part), Periodon hankensis Biozone, Periodon aculeatus Superbiozone (including the Histiodella labiosa, Histiodella holodentata, Histiodella kristinae, Pygodus serra and Pygodus anserinus biozones) and the Periodon grandis Biozone. The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones. This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally.