Latest Cambrian-earliest Ordovician conodonts from far western New South Wales and their biostratigraphical significance

This report documents the conodonts recovered from the Andersons Tank Limestone Member (new name) and calcareous siltstone lenses within the Scropes Range Formation and from the Kandie Tank Limestone within the Kayrunnera Group of the central-southern Koonenberry Belt in far western New South Wales, Australia. Among 18 identifiable conodont species are two new species, Paltodus simplex sp. nov. and Variabiloconus delicatus sp. nov. The conodonts confirm that the age of the Kandie Tank Limestone extends from the latest Cambrian (Cordylodus proavus Biozone) to Early Ordovician (Chosonodina herfurthi Biozone), partly contemporaneous with the Andersons Tank Limestone Member that ranges from the latest Cambrian Cordylodus proavus Biozone to possibly earliest Ordovician (Cordylodus lindstromi Biozone). Occurrence of the index species Iapetognathus fluctivagus and Iapetonudus ibexensis in the middle part of the Kandie Tank Limestone provides direct correlation to the base of the Ordovician System defined at the Green Point section in western Newfoundland of North America, and to sections in Asia and South America. These new data have significantly improved our current understanding of the Ordovician biostratigraphy in the region and more broadly the geological history and evolution of the eastern Gondwana margin during the early Paleozoic. We provide detailed morphological comparison and formal designation of the lectotypes for the four species (I. fluctivagus, Iapetognathus jilinensis, Iapetognathus landingi and I. ibexensis) critical for defining and globally correlating the basal Ordovician.