The interpretation of a reconnaissance gravity survey of north Queensland has shown that the area is composed of normal continental crust approximately 40 km thick, and is consistent with relief at the Moho of approximately 7 km. The parameters required for three-dimensional crustal gravity modelling, crustal thickness and density contrast across the Moho, were derived from available crustal seismic refraction experiments, together with analyses of correlations of crustal parameters on a worldwide basis. There are no large departures from isostatic equilibrium in the area. The southeastern part of the area is isostatically compensated and the crustal thickness reaches 43 km. The Mount Isa Block is not isostatically compensated and coincides with an area of thin (38 km) crust. This area is stable and, because of its size, is unlikely to achieve local isostatic equilibrium. The Cape York area has not reached isostatic equilibrium. The gravity anomaly pattern suggests that this area may have approached equilibrium progressively, with those parts of the area farthest from the centre of the Tasman Geosyncline having the smallest departure from isostatic equilibrium. This agrees with the history of development of the northern part of the Tasman Geosyncline, which youngs to the north and east. The Palmerville Fault is a major surface structure, but has no gravity effect originating at Moho depths, and hence may be only an upper crustal feature. The Coen Inlier also has little or no influence on the regional Bouguer anomalies, and is therefore probably a shallow crustal feature, of less significance than its surface outcrop suggests. The Cape York-Oriomo Ridge, however, has little surface expression, but is shown by the gravity data to be a major feature of the crust.

The Great Artesian Basin occupies 1.7 X 10^6 km^2, or about one-fifth of Australia, extending across parts of Queensland, New South Wales, South Australia, and the Northern Territory. It underlies arid and semi-arid regions where surface water is sparse and unreliable. The discovery of the basins groundwater resources around 1880, and their subsequent development, have allowed an important pastoral industry to be established. Pastoral activity and town water supplies are to a very large extent dependent on artesian groundwater. The groundwater basin consist of a multi-layered confined aquifer system, with aquifers occurring in continental quartzose sandstones of Triassic, Jurassic and Cretaceous age. The intervening confining beds consist of siltstone and mudstone; a thick argillaceous sequence of sediments of marine origin and Cretaceous age forms the main confining unit. The basin is, in places, 3000 m thick, and forms a large synclinal structure, uplifted and exposed along its eastern margin and tilted southwest. Recharge occurs mainly in the eastern marginal zone, and large-scale groundwater movement is generally towards the southwestern, western and southern margins. Natural discharge occurs from spring in these areas; most springs are connected with structural features. Minor recharge occurs in the western margin. The potentiometric surfaces of the Triassic, Jurassic and Early Cretaceous aquifers are still above groundlevel in most areas of the basin. Considerable lowering occurred in heavily developed areas; from about 1880 to 1970, regional differences of up to 80 m were recorded, and in some areas waterwells ceased to flow. Water levels of some Cretaceous aquifers are below the groundsurface throughout most of the basin area. Hydraulic gradients of the main aquifers in the Lower Cretaceous-Jurassic sequence are about 1:2000, and of aquifers in the Cretaceous sequence 1:1800. Transmissivity values of the main aquifers in the Lower Cretaceous-Jurassic sequence, from which most flowing artesian wells obtain their water, usually are several tens to several hundreds m^2/day. Hydraulic conductivities range from 0.1 to 10 m/day, with a predominance in the lower part of the range. Storage coefficients, as interpreted from wire-line logs, average about 10^-5. Aquifer thicknesses range from several metres to several hundred metres. Average groundwater velocity in the eastern marginal parts is from 1 to 5 m/year. Environmental isotope analysis shows that the artesian water is of meteoric origin. About 4700 flowing artesian wells have been drilled to depths of up to 2000 m, but average 500 m. Individual flows exceeding 10 000 m^3/day have been recorded. About 3100 wells remained flowing during the early 1970s, when the accumulated artificial discharge was about 1.5 X 10^6 m^3/day, as compared to the maximum flow from the basin of about 2 X 10^6 m^3/day from about 1500 artesian wells around 1918. The high initial discharge in the early years of exploitation, which was caused by the release of pressure in the aquifers, gradually levelled off, and has now approached a steady-state condition, in which total basin discharge is roughly balanced by recharge. Non-flowing artesian water-wells mainly in the higher Cretaceous aquifers number about 20 000, and are generally shallow, up to several hundred metres deep, and are usually equipped with windmill-operated pumps, supplying on average about 10 m^3/day each. Most flowing wells occur in the marginal areas of the basin, as the main aquifers in the Lower Cretaceous-Jurassic sequence which they tap are too deep for economical abstraction in the central part of the basin. In the central part mainly non-flowing shallow wells are found.

Large trilobite resting traces (Rusophycus) from the Mithaka Formation are up to 30 cm or more in length, and are found in association with asaphid trilobites of similar length. The portion of the Mithaka Formation in which the Rusophycus occur contains a rich fauna and ichnofauna, and is considered to have been deposited in very shallow-water marginal to wide intertidal barrier flats behind a sand barrier.

Tightly folded migmatitic rocks, intruded by 1860 Ma granite and younger felsic and mafic dykes, are exposed in a band 95km long and up to 10km wide along the western part of the Kalkadoon-Leichhardt Belt. The migmatites are considered to represent the basement underlying Proterozoic cover rocks, the oldest of which are Ma felsic extrusives (Leichhardt Volcanics) about 1860 Ma old. The migmatites include thinly banded gneiss with mainly concordant leucosomes (metasediments), non-banded gneiss with wispy leucosomes (metavolcanics), and nebulitic granitic gneiss (meta-intrusives). Metamorphism and deformation of the migmatites took place before the intrusion of a cross-cutting granite dyke dated at 1860 ± 32 Ma by U-Pb zircon. Another U-Pb zircon age, 1850 ± 16 Ma, obtained for a migmatitic metadacite, is anomalously young, although within experimental error of a preferred migmatisation age of 1860 - 1870 Ma. Uplift rates of 2-5 mm a year are implied, to account for the inferred brief interval between migmatite formation and ensuing felsic volcanism.

Magnetotelluric techniques have been used to investigate structural trends in the McArthur Basin . Observations were made at 34 sites, extending 450 km across the Wearyan Shelf, the Batten Fault Zone, and the Bauhinia Shelf. For sites on the Wearyan Shelf, the orthogonal components of resistivity are generally similar, suggesting continuous horizontal strata and uniform basement depths. However, lateral changes in resistivity, evident on the Bauhinia Shelf, become extreme in the Batten Trough. For sites near the Emu Fault, the two components diverge at long periods, indicating a major change in structure with a pronounced vertical contact. Resistivities associated with the Tawallah Group appear distinct enough to show that no appreciable thickness of McArthur Group can be present east of the Emu Fault. The data are consistent with geological models based on the assumption that the Batten Trough formed as a syndepositional graben with rapid changes in depositional thickness at the boundary faults.

The Proterozoic I-type Kalkadoon and Ewen Batholiths and their comagmatic extrusive equivalents, the Leichhardt suite, form an association covering at least 5000 km2 in the central part of the Mount Isa Inlier. U-Pb zircon data and some Rb-Sr total rock data show that these rocks crystallised from melts emplaced between 1840 and 1870 m.y. ago and are the oldest dated igneous rocks in the Inlier. Chemically and isotopically, these granites are relatively uniform and, compared with most other Mount Isa granites , they have higher Sr and Al2O3 contents, and lower TiO2 , Zr, Nb, and Th contents . These chemical characteristics appear to be restricted to felsic igneous rocks known to be older than 1800 m .y. and may be useful in identifying the older felsic melts of the Mount Isa Inlier. The source for the rocks of the Kalkadoon- Ewen- Leichhardt association is estimated to have had an SiO2 content of 55-60 per cent. Relative to other large Palaeozoic and Mesozoic I-type batholiths elsewhere, this Mount Isa association is enriched in K20, Rb, Th, U, La, Ce, Zr, and Nb, and depleted in CaO, MgO, Ni, and Cr. The least isotopically disturbed granites of the association have relatively low initial 87Sr/86Sr ratios (about 0.704), which implies that the age of the source for these melts was not much older than the age of their emplacement. As chemically and isotopically similar granites occur in most Proterozoic areas of Northern Australia, it is inferred that during the period 1900-2100 m.y. a significant mantle differentiation event took place, during which large volumes of material were accreted to the base of the crust in these areas. Post-emplacement metamorphism and deformation , which have a maximum age of 1640 m.y. , caused significant textural and mineralogical changes in the Kalkadoon Batholith, but had a lesser effect on the Ewen Batholith . Igneous textures are commonly preserved in the Ewen Batholith, but the Kalkadoon Batholith, which has been metamorphosed from lower greenschist to upper amphibolite grade, shows significant isotopic disturbances.

Discussion on paper by Derrick (1982) focussing in particular on (1) definition of the Leichhardt River Fault Trough (LRFT); (2) nature of the western margin of the LRFT; and (3) the extent of the Mount Gordon Arch.

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.

Sediment and water flux were monitored at Boulder Reef, in the Northern Great Barrier Reef, before, during, and after the passage of Tropical Cyclone Dominic. Rainfall at Cooktown as a result of Dominic amounted to 430 mm in 3 days, this effecting a record discharge in the Endeavour River of nearly 50 000 megalitres/day. At Boulder Reef, conditions prior to Dominic of 10-20 knot winds effected average water velocities of 11 cm/s across the reef, which generated a substantial reef-derived sediment load with particulate organic material up to ten times greater than particulate inorganic carbon by weight. During the high-energy event, winds in excess of 50 knots generated water movements of up to 40 cm/s and sediment loads two to five times greater than before the event. In addition, the sediment contained a substantial terrestrial component (illite and kaolinite), probably originating from the Endeavour River. Three days after the passage of Dominic, water velocities across the reef were still rapid (up to 60 cm/s) and sediment loads still high, although now only reef-derived. However, further monitoring indicated a second pulse of terrigenous material reaching Boulder Reef four days after Dominic. Large amounts of reef-derived carbonate and organic material are lost daily from the system to the inter-reef areas. Conversely, large quantities of terrestrially derived clay are added to the reef every five years or so, in amounts within the range 135- 228 tonnes: this has probably occurred at this periodicity for the past 5000 years. Cores through the Holocene section confirmed that clay deposition has occurred throughout its growth.

Chemical and isotopic characterisation of Recent sediments from Princess Charlotte Bay reveal a broad homogeneous sediment that has only a slight increase in CaC03 content from the shore to the reef. Carbon isotopic ratios of the organic fraction indicate that the carbon is 95 per cent oceanic. Kaolinite content is uniform at 4 weight per cent. The change from terrestrial/river to lagoonal sediment characteristics is sharp and occurs within 1km of the shoreline. The change from lagoonal to reefal sediment characteristics is equally as sharp and may be localised. The term near-shore mud is preferable to terrigenous mud. Sedimentation rates are in the range 2.3-6.1 mm/yr. with mixed layers up to 10 cm thick, as determined by the 210Pb method. 137Cs determinations of sedimentation rate are not in disagreement, but are likely to yield ambiguous results in the Great Barrier Reef Province, because of diffusive redistribution, owing to the low distribution coefficient, KD = 420-800, measured in lagoonal sediments.