?roc. R. Soc. Qd 87: 63-76. pis. 3 - 'i. (1976) ISSN 0080-469 Geology and Lower-Middle Devonian Coral Conodont Biostratigraphy of the Nogoa Anticline, Springsure District, Central Queensland Barry G. Fordham Department of Geology and Mineralogy, University of Queensland, Brisbane SYNOPSIS The Nogoa Anticline exposes the Lower-Middle Devonian Dunstable Beds which form the basement to the Upper Devonian-Lower Carboniferous Drummond Basin sequence. The Dun- stable Beds (base unexposed) are a 1000+ m thick sequence of intermediate vo . .:anics and pyro- clastics interbedded with shales. Towards the top of the formation, limestone lenses containing late Emsian and early Eifelian coral-conodont faunas appear to represent a back reef environment. An unconformity, representing northwest tilting of the Dunstable Beds, spans the rest of the Middle Devonian and precedes the Upper Devonian (380 x 10" yrs) Silver Hills Volcanics of the Drummond Basin sequence. This 700 m thick formation contains a lower unit of intermediate volcanics and acid ignimbrites, a middle unit of floodplain sediments interbedded with trans- gressive lagoonal limestones, and an upper unit of intermediate volcanics. The unconformably overlying Upper Devonian-Lower Carboniferous 'conglomerate group' of the Telemon Formation comprises 630 m of volcanogenic floodplain sediments. Middle Carboniferous deformation has produced folding and associated faulting of the units. An alkali(?) basalt sill, intruding the middle unit of th& Silver Hills Volcanics, probably belongs to the Oligocene volcanic phase of central and southern Queensland. INTRODUCTION The Nogoa Anticline contains Lower to Middle Devonian rocks of the Anakie High and Upper Devonian to Lower Carboniferous rocks of the Drummond Basin. The core ofthe anticline is exposed as a northeast trending inlier on either side of the Nogoa River, 40 km west-southwest of SpringsOre in the northern part of the Springsure 1:250,000 Sheet area. Geological investigation of the Nogoa Anticline was begun by geologists of the Shell (Queensland) Development Pty Ltd (Shell, 1952) who produced a map and a stratigraphic sequence of the area. Hill (in Shell, 1952) identified a coral fauna from limestone lenses within the Dunstable Beds (referred to therein as Dunstable Series) and later (Hill, 1957), based on Shell's report, formalized the stratigraphic units according to the Australian Code of Stratigraphic Nomenclature. The known geology of the area was summarized by Tweedale (1960) as part of a compilation of the Devonian and Carboniferous geo- logy of Queensland. Richard (1963) conducted a photo-interpretative survey of the Springsure 1:250,000 Sheet area and results of magnetic and gravity geophysical investigation in the Sheet area were published by Starkey and Warren (1959), Robertson (1961), and Mollan etal. (1964). Hill (in Veevers, Mollan et al., 1964) identified corals from additional localities in the Dunstable Beds, for comparison with a fauna from Glendarriwell homestead in the Emerald Sheet area. Work by the Bureau of Mineral Resources and the Geological Survey of Queensland (e.g. Mollan et al., 1964, 1969; Mollan, 1967; Olgers, 1972) reinterpreted the geological structure and thereby completely revised the stratigraphy. Telford (1972 and in press) identified from the Dunstable Beds a conodont fauna which permitted correlation of the beds with other eastern Australian units. In 1973 the author mapped an area of 19 km 2 encompassing the exposed core ofthe Nogoa Anticline . (Fig. 1). Grid references cited herein refer to Fig. 1 and correspond to that of the Springsure 1:250,000