Late Cambrian trilobites from the Chatsworth Limestone, western Queensland

The trilobite faunas described in this Bulletin are exclusively from the Chatsworth Limestone sensu stricto, as it occurs in the immediate neighbourhood of Chatsworth Homestead, 80 km south-southeast of Duchess, in western Queensland (Fig. 1). The outcrops straddle the Duchess and Boulia 1:250000 Sheet areas, and form the central portion of the Burke River Structural Belt (Shergold, 1975, pp. 4-7; in Shergold, Druce et al., 1976, pp. 4-5). "Although trilobites have been described (Opik, 1963, 1967) from the underlying Pomegranate Limestone, at Pomegranate Creek, 19 km north of 'Chatsworth', no material from the Chatsworth Limestone s.s. has been illustrated previously. Those trilobites presently described are from collections made during initial field mapping of the Boulia Sheet area in 1957-60 (Casey, 1968; Casey et al., 1960), and the Duchess area in 1958 (Carter & Opik, 1963; 6pik, 1963). Frome-Broken Hill Pty Ltd collected two samples from the basal Chatsworth Limestone near 'Chatsworth' in 1958 (Taylor, 1959). Subsequently, collections were assembled by the BMR Northwest Queensland Phosphate Group in 1967 (de Keyser et al., in de Keyser, 1968), by the author in 1969, and by B.M. Radke during the course of 1:100 000 scale mapping. by the BMR Georgina Basin Project in 1974-75. Material is also currently. Available from two BMR stratigraphic boreholes, Boulia No. 6 and Duchess No. 13 (Fig. 2 and Appendix 3), drilled for the Georgina Basin Project in 1974. All material described in this Bulletin is deposited in the Commonwealth Palaeontological Collection (prefix CPC), housed in the Bureau of Mineral Resources, Canberra, Australia. Acknowledgements The author acknowledges the time consuming aid given by H.M. Doyle (BMR) in the preparation of the photographs used herein. B.M. Radke (BMR) is thanked for permitting the reproduction of the Lily Creek section which he measured, and J.M. Kennard (BMR) for making available details of cores logged, and for providing petrographic descriptions of the rocks noted in Appendices 1 and 3. I appreciate the constructive criticism provided by Drs R.A. Henderson, James Cook University of North Queensland, and J.B. Jago, South Australian Institute of Technology, on an earlier draft of this Bulletin. The drawings were prepared by R. Fabbo and G. Clarke of BMR's Cartographic Section.