The central Great Barrier Reef Province is characterised by a mainland prograding terrigenous clastic shoreline and an inner shelf dominated by fluvially derived mud. The Burdekin River acts as a large point source of sediment, which is dispersed to the northwest of the mouth. Fluvial sand is wholly contained within the coastal zone and the sand and gravel components of inner and middle-shelf sediments are largely relict or palimpsest. Vertical accumulation of terrigenous mud is limited to a thin veneer on the inner shelf and is negligible on the middle shelf. Coastal progradation accounts for the bulk of Holocene terrigenous sedimentation, which decreases in a northwesterly direction, from 2.5 m yr-1 at the present delta front to 0.1 m yr-1 on the coastal plain north of Townsville. Progradation of the shoreline occurs as four distinct sedimentary assemblages (beach-ridge plain, chenier plain, mangrove-mud-flat plain, and barrier bar-lagoon complex). The overall prograding coastal wedge, where preserved in the geological record, would have recognisable seismic stratigraphic elements (coastal onlap and toplap, distal down lap and marine offlap). The pattern of late Quaternary sea-level oscillations suggests that terrigenous marine and/or alluvial sediments should predominate across most of the shelf of the Great Barrier Reef lagoon.

Fringing reefs and storm ridges, from inner-shelf sites on the Great Barrier Reef between 14° and 20° S, are examined for Holocene sea-level and climatic changes. The sites all lie close to the line along which the sea level of 5500 yr B. P. is thought, on isostatic grounds, to have been + 1 m. Coral microatolls are used as indicators of former sea levels on fringing reefs. 45 radiocarbon results from 11 sites range between 360 and 5855 yr B. P., and their age/height distribution shows that sea level fell smoothly from + 1 m at 6000 yr B. P. to its present position. Confidence limits on the sea-level trend are ±0.2 m; and no evidence for secondary oscillations of sea level has been found. With reference to climate, coral shingle and shell storm-ridge sequences at 5 places (total of 8 traverses) were surveyed and dated. Results from the best sequence (Princess Charlotte Bay) show that the average recurrence interval of major ridge-building storms is about 80 yr. Statistics of the series of storm-ridge ages do not show any identifiable changes in frequency of ridge building over the last 4000 yr and perhaps 6000 yr. It is concluded that evidence for climatic changes in the northern Great Barrier Reef in the last 6000 yr has not yet been found. The direction of continuing studies is outlined.

The Cainozoic evolution of the central Great Barrier Reef Province has been deduced from shallow, intermediate, and deep focus seismic reflection profiling. For much of its history the province has been dominated by terrigenous sedimentation , principally controlled by the relative height of sea level. The earliest depositional episode recognisable beneath the continental shelf was the infilling of the Queensland Trough rift basin with alluvial fan and trunk stream deposits in the Late Cretaceous to Paleocene. As the region subsided further, this was replaced by a Paleocene to Eocene marginal and shallow marine coastal and marine onlap phase. Three periods of low sea level in the late Oligocene, late Miocene, and late Pliocene to Pleistocene resulted in alluvial sedimentation across the shelf, and fluvial and wave-dominated deltaic progradation at the shelf edge, which produced 10-40 km of shelf out-building. During the intervening periods of high sea level, sedimentation was restricted to coastal deltaic progradation on the inner shelf and onlap of the continental slope by submarine fans, and the upper slope was extensively eroded. The reef facies may have first appeared as a fringing reef in the Eocene, but was only established as an extensive, apparently shelf-dominating facies during high sea levels associated with Pleistocene aggradational phases. The reefs, which appear to be only 150-250 m thick, grew on and occur within siliciclastic fluviatile and deltaic sediments, and not on antecedent carbonate platforms. Reef growth occurred during short periods of high sea level, and during the intervening and longer periods of low sea level the reefs were eroded subaerially. Continual re-colonisation of sites throughout their growth history has produced reefs that are composite features made up of a series of remnant reefs separated by unconformities. A shelf-edge barrier reef system, now generally submerged, occurs along much of the central Great Barrier Reef Province, except near Palm and Magnetic Passages. This has modified upper slope deposition during periods of low sea level by funnelling fluvio-deltaic sediments through gaps in the barrier reef, directly feeding upper slope canyons and depositing submarine fans on the middle and lower slopes. During periods of high sea level the barrier reef has shed fine-grained carbonates and organic material to the upper slope. It appears that the central Great Barrier Reef region is unlikely to have been a major reef carbonate province at any but the most recent stage of its evolution.

Entropy-ratio maps enable mapping of surficial facies of coral reefs at any chosen resolution. A ternary classification uses detritus, framework encrustation, and pavement as end-members, and is subdivided on the degree of mixing of these. The classification is sensitive to all reef environments, particularly to zonation across reef flats. It can also be superimposed on other classifications. An example is given of its use in the Great Barrier Reef.

In the Georgina Basin, the Toko Syncline is considered the most prospective region for petroleum exploration. The syncline contains up to 5000 m of Middle Cambrian to Middle Ordovician sediments and has been the site of six petroleum exploration wells, three of which showed traces of gas, oil, and solid bitumen. Geochemical data for cores from two stratigraphic holes, GSQ Mount Whelan Nos. I and 2, and data from four exploration wells, held on open file at BMR, are used to evaluate the organic maturation and rock potential of the sediments in the Toko Syncline. Source rocks are not recognised in the Ordovician; however, source rocks of generally good quality are present in the Middle and Upper Cambrian. While doubts do exist over the stratigraphic correlations for the wells involved in this study, the Middle Cambrian Marqua beds are considered to be the best source interval. Maturity for oil generation is achieved in the Upper Cambrian to Lower Ordovician Ninmaroo Formation at the Mount Whelan location. However, in the deeper western area, where the better exploration prospects are likely to exist, maturity in Mirrica No. 1 is reached in the Lower to Middle Ordovician Carlo Sandstone. Over-maturity for oil generation, but still in the gas generation phase, is generally observed in the Middle Cambrian. An oil stain in the Lower Ordovician Coolibah Formation in GSQ Mount Whelan No.2 (also described as bitumen plugging porosity) is interpreted as having originated in and having migrated from the Cambrian source rock intervals.

Recent mapping in the Duchess-Urandangi region, covering most of the southern part of the Mount Isa Inlier, has shown that felsic and mafic volcanics occur in most Precambrian stratigraphic units exposed there. Five distinct geochemical suites of felsic volcanics are recognised, each suite probably having been derived from a chemically unique crustal source region. The Leichhardt suite is distinguished by high Sr, and low Zr, Nb and Y abundances, whereas the Argylla suite has low Sr and very high Zr and Nb concentrations. The Bottletree suite is characterised by high Ba, Sr, Zr, and Nb, the Duchess-Corella suite by low Sr and Zr, and high Nb and Y contents, and the Carters Bore suite by high K2O and low Al2O3, Na2O, CaO, Pb, Sr, and Ba. Most of the analysed mafic volcanics from the region are chemically similar, and there is no systematic change in composition from west to east. The mafic volcanics are characterised by low incompatible-element contents and are similar chemically to continental tholeiites of the Karroo province of southern Africa. Silica values for the volcanics and their intrusive equivalents show a well-defined bimodal distribution, probably indicating an extensional crustal regime.

At the Mammoth mine, epigenetic copper mineralisation occurs within the Myally Subgroup of the Haslingden Group, an arenaceous sequence that both includes and overlies basic volcanics. A basic flow in the Myally Subgroup is altered, being enriched in potassium and copper for up to 200 m from the mineralisation. However, underlying metabasalts of the Eastern Creek Volcanics up to 600 m from the mineralisation are depleted in iron and copper and enriched in potassium relative to those further away. Evidence is presented that the Mammoth ore represents copper leached from the Eastern Creek Volcanics and transported along the Mammoth-Mammoth Extended Fault system. This hypothesis is similar to one previously proposed for the copper mineralisation at Mount Isa, although there are differences in the age and lithology of the host rocks in the two areas. Thus, rocks adjacent to major faults transgressing the Eastern Creek Volcanics must be considered prospective for copper mineralisation.

The Lawn Hill Platform Cover comprises a sequence of mildly deformed Proterozoic sediments and volcanics that crop out northwest of Mount Isa. Three subdivisions are recognised in the sequence: basal coarse clastics and acid and basic volcanics - the Bigie Formation and Fiery Creek Volcanics. They are overlain unconformably by fine to coarse fluvial and shallow marine clastics (the Surprise Creek Formation). The third, uppermost, and major subdivision of the platform cover, the McNamara Group, overlies the Surprise Creek Formation with minor unconformity. It consists of basal clastics, a thick sequence of carbonates, and an upper deep-water clastic sequence. The Lawn Hill Platform Cover is deformed into basins and domes, commonly intersected by major northeast and northwest-trending faults. Economic Cu, Pb and Zn sulphide deposits within the Lawn Hill Platform Cover are concentrated at two main stratigraphic horizons in the lower middle McNamara Group. The main deposits are associated with carbonaceous shales or laminated algal dolomite, suggesting that they may be formed by reduction of base metal rich solutions at an early diagenetic stage by the action of decaying algal material.

Several breccia bodies consisting of randomly oriented angular to rounded fragments of locally derived amphibolite-grade metamorphic rocks dispersed in an igneous-textured pink matrix occur in the southern part of the Proterozoic Mount Isa Inlier, where they have been mapped as Mount Philp Breccia. The fragments in the breccia can be matched with rocks in the adjacent Corella Formation, a unit of mainly calc-silicate rocks. The breccia matrix contains stubby phenocrysts of tremolite and small miarolitic cavities set in a ground mass of interlocking albite laths. The breccia bodies postdate the deformation and metamorphism of the enclosing Corella Formation, and are thought to fill pipes and fissures formed by explosive releases of pressure during intrusion of magma into calc-silicate rocks at depth.

Fifteen of 27 potential planktic foraminiferal biostratigraphic events from the latest Pliocene-Holocene have been examined; most of the early Pleistocene was not able to be studied because of a hiatus in the one core which penetrated through the Pleistocene into the top of the Pliocene. Four of these events have been recognised for the first time, and some have been used to establish a formal zonal and subzonal scheme for the region. Two new subzones are proposed, the Globigerinoides quadrilobatus fistulosus Subzone (for the basal part of Zone N.22) and the Bolliella praeadamsi Subzone (for the top part of Zone N.22). These changes have made necessary the redefinition of both the Globorotalia (Truncorotalia) crassaformis viola and the Globorotalia (Truncorotalia) crassaformis hessi Subzones. There is little evidence that changes in palaeoceanographic conditions are related to the faunal changes observed in the cores, although there are strong indications of reworking at some levels within some of the cores (such as late Miocene Zone N.17 in one core), which may have been related to sea-level fluctuations. The assemblages from the cores show a marked stability, with the faunas being dominated by spinose, oligotrophic taxa. Temperate water forms are either very rare or absent, whereas tropical and subtropical species are dominant. A single new species, Bolliella praeadamsi has been described because of its biostratigraphic utility. This species is an evolutionary intermediate between Bo. calida praecalida and Bo. adamsi.