This data package was preduced in response to a request by Rodney King from Teck Australia for a compilation of GA borehole datasets from the Isa Superbasin, in particular for gamma-ray data. The data set includes drill hole/section location information, and lithological, geochemical and gamma ray data. All data were extracted from GA databases.

The Delny-Mount Sainthill Fault System, a distinctive feature on satellite photographs, can be traced as a well-developed geological and geophysical feature extending some 130 km across the Arunta Block, central Australia. It has a slightly north-of-west trend, from 4 km south of Mount Thring (22°49S, 136°02E) to 5 km south of Delny Outstation (22°33S, 134°49S) (Figs 1, 2). The deformed nature of the rocks at Mount Saint4iIl was first noted by Smith and others (1960), who described a blastomylonite derived from nearby granite, and recorded the gradational contact between deformed and undeformed units. Shaw and Warren (1975) mapped the Delny section of the Fault System. The nature of the remainder of the Fault System and its continuity was recognised during rapid reconnaissance to provide data for interpretation of new coloured aerial photography in the 1976 field season.

The Oenpelli Dolerite comprises at least four major sheet-like intrusions up to 250 m thick of continental tholeiitic composition, which have a lateral extent of about 20 000 km^2. The intrusions were emplaced at about 1720 m.y. into Lower Proterozoic metasediments of the Pine Creek Geosyncline, and postdate an 1880 m.y. regional metamorphic event. The intrusions consist of symmetrically differentiated layers of olivine dolerite, minor felsic differentiates, and rare crosscutting gabbroic pegmatites. Within the thicker sheets minor rhythmic layering is found in olivine dolerite. The Oenpelli Dolerite contains normative orthopyroxene and the major and trace element chemistry closely parallels the trends of major continental mafic tholeiitic suites. Projection of the chemical data into the anhydrous CMAS system shows that the rocks crystallised in the pressure range 1 atmosphere to 5 kb. The close match between the observed equilibrium and the 1 atmosphere phase diagrams for dry tholeiitic magmas suggests that the last equilibration of these magmas was at very low pressure. It is concluded that the tholeiitic Oenpelli Dolerite rocks have evolved by polybaric olivine fractionation during slow, or intermittent, uprise from higher magnesia magma generated by partial melting within the upper mantle; plagioclase is an additional liquidus phase at shallow-crustal levels.

All the uranium deposits of the Alligator Rivers Uranium Field of Australia, which between them contain a quarter of the worlds reasonably assured uranium resources, are strata-bound within the Cahill Formation. Three of the four economic deposits are more or less conformable within a lower member near the base of the formation, which contains carbonate and carbonaceous rocks. The formation forms a poorly exposed but continuous folded belt, 5 km or more wide, over an area of about 15 000 square kilometres. Exposure is sparse, the rocks are generally deeply weathered, and knowledge of the stratigraphy of the unit is based largely on the results of shallow stratigraphic drilling. Quartzo-feldspathic and micaceous metasediments are the dominant rock types in the Cahill Formation as a whole, and they have been metamorphosed to the amphibolite grade (staurolite-almandine subfacies). The unit appears to unconformably overlie the Archaean-Lower Proterozoic granite-gneiss-migmatite Nanambu Complex and the Lower Proterozoic psammo-pelitic Mount Partridge Formation, and is overlain, in places unconformably, by the Fisher Creek Siltstone. It grades into the migmatite-gneiss-granite terrain of the Nimbuwah Complex in the north-east. The formation is a facies equivalent of the Koolpin Formation (host to uranium mineralization in the South Alligator Valley uranium field) to the south, and, in places, was separated from it during deposition by a basement high of Mount Partridge Formation. The carbonate-carbonaceous sequence was probably deposited under shallow near-shore shelf conditions, along with considerable admixed terrigenous material. The upper part of the formation represents a period of transgression over the shelf. Uranium was concentrated under reducing conditions which developed locally in many places within the carbonate shelf. Subsequent concentration and reconstitution took place a number of times, the main period being during 1800 m.y. regional metamorphism and deformation. Mobilization of uranium away from the carbonate-carbonaceous sequence took place only under high temperature and pressure conditions such as those attending formation of the Nimbuwah Complex, where the metal was relocated in favourable low pressure structures.

Small nodules and tabular bodies of practically pure micro-crystalline magnesite up to a few centimetres across occur in late Cainozoic calcrete around Gosses Bluff. The calcrete underlies an area of about 15 km^2 and the magnesite constitutes somewhat less than 1 per cent of the outcrop. The bedrock in the area of calcrete is impact breccia of the Gosses Bluff structure. The superficial weathered products of these breccias constituted a suitable host rock for the calcrete because of their inherent permeability and their position in topographically low areas. The source of magnesium carbonate was most likely in the Late Proterozoic and Palaeozoic dolomites and magnesian limestones exposed to the north in the MacDonnell Ranges. Petrographic evidence from the random samples of calcrete collected at Gosses Bluff suggests that the history of the deposit commenced with invasion of magnesium carbonate rich waters and formation of small bodies, probably of a metastable hydrate of magnesite which later reverted to the stable phase. A period of sub-aerial dessication ensued and caused disintegration of the nodules and production of cracks and voids. Phreatic water enriched in calcium carbonate invaded the deposit; voids were lined with fibrous calcite, smaller cracks were completely filled, and at the same time the magnesite was replaced, in part, by calcite. The larger voids were subsequently filled by calcrete which consisted of a mixture of disintegrated breccia fragments, chiefly quartz, feldspar and quartzite grains, with the addition of a minor proportion of magnesite grains incorporated from the nodules; and an abundant matrix of calcite. There is scant reference to magnesite in calcretes elsewhere in Australia, possibly because magnesite is not readily distinguished in some fine-grained calcretes.

The Lander Trough forms the east-southeast trending, southern and deeper part of the Wiso Basin, and is flanked on the north by an extensive less deformed area of the Basin. Recent geological mapping, shallow stratigraphic drilling, and a reassessment of geophysical data in the southeastern part of the trough provide additional information on the nature and structure of the rocks it contains. Beneath the Cainozoic superficial material, three sequences of rocks are distinguished. The upper sequence consists of ?Late Palaeozoic Lake Surprise Sandstone; the middle of Cambrian or Ordovician sediments and volcanics; and the lower of Proterozoic rocks. The ?Late Palaeozoic sequence is flat-lying and thin (100-250 m), whereas the Early Palaeozoic sequence forms a wedge which thins to the north and thickens southwards to about 800 m In the deepest part of the trough. The Proterozoic sequence forms the basement to these Palaeozoic sediments of the Wiso Basin. The trough is indicated to be a downwarp in the crust, about 300 km long and 100 km wide, bounded by an overthrust fault system against the Arunta Block on the south. The fault system is considered to be contemporaneous with the post-Devonian Alice Springs Orogeny which affected the NgaIia and Amadeus Basins farther to the south. The presence of a thick (up to 800 m), partly marine sequence of Cambrian and Ordovician sediments upgrades the petroleum potential of the Lander Trough area, as gas has been found in such sediments in the depositionally and structurally similar Amadeus Basin to the south, and the Toko Syncline of the Georgina Basin to the southeast.

A recently discovered Templetonian (Middle Cambrian) trilobite fauna, with affinity to that of the Beetle Creek Formation of western Queensland, is reported from pebbles derived from the Elcho Island Formation (Wessel Group) on Elcho Island, in the Arafura Basin, northern Australia. Consequently, a previously determined isotopic age of 790 m.y., on glauconite from the Elcho Island Formation, is now clearly much greater than the age of deposition of the formation, and the age of the occurrence of Skolithos at the base of the Wessel Group (Buckingham Bay Sandstone) can be reconsidered as Early or early Middle Cambrian, rather than late Proterozoic. Regional correlation of the Buckingham Bay Sandstone and Raiwalla Shale of the Arafura Basin with the Bukalara Sandstone and Cox Formation of the McArthur River region is reiterated on the basis of rock types and presence of the trace fossil Skolithos.

Nettletons concept of density profiling can be utilised to give useful estimates of the bulk density of topographic features. These estimates can be used to infer the composition of such topography, or to assist in the interpretation of local gravity anomalies. Two methods that facilitate multiple density profiling over elongate topography are presented. One is a simulation reduction method utilising the two-dimensional line integral formula of Talwani, Worzel and Landisman (1959). It enables data from any detailed gravity traverse crossing an elongate topographic feature at right angles to be automatically reduced by computer to a set of multiple density Bouguer profiles. From these profiles, the bulk density of the topographic feature can be estimated by visual correlation. The other is a graphical method of converting a set of multiple density Bouguer profiles directly to point density estimates, without the need for visual correlation. Both methods are theoretically exact for the ideal case. A visual correlation determination of 2.85 ± 0.05 g cm^-3 is demonstrated for a traverse crossing the 300 m high Harts Range, Northern Territory, and three point determinations of 2.97,2.97, and 2.99 g c^-3, for a traverse crossing the 100 m high Fraser Range, Western Australia.

Carbonaceous clays in a stratigraphic borehole near Napperby homestead, in the southern part of the Northern Territory, have yielded a microfloral assemblage comprising over thirty form-species of pollen. The assemblage can be referred to the middle Eocene Proteacidites confragosus. Zonule on the basis of the presence of the nominate species, and is the most inland of any Australian Tertiary flora described. The Napperby sediments may be correlated, on a palynological basis, with the upper part of the Eyre Formation of northeastern South Australia; they are older than the vertebrate-bearing Waite Formation of the adjoining Alcoota Sheet area. A high frequency of pollen from aquatic and marsh-loving angiosperms and the presence of dinoflagellate cysts indicates deposition under lacustrine conditions. The presence of Nothofagus and podocarpaceous pollen types in significant amounts suggests that a humid climate prevailed, although seasonal aridity cannot be ruled out.

The Karumba Basin in its present form coincides areally with the Gulf of Carpentaria and the river systems draining into it. The Basin is mainly of Cainozoic age, epi-cratonic, and superimposed on the Mesozoic Carpentaria Basin of the Trans-Australian Platform Cover. The development of the Karumba Basin related to the separation of Australia from Antarctica, and to subsequent plate margin events in New Guinea, in contrast to the evolution of the Carpentaria Basin which probably correlated with plate convergence to the east. The structural basin contains four main sets of deposits, each primarily resulting from an uplift episode. The oldest set, the Bulimba Formation, is probably of late Cretaceous-Paleocene age; the next, the Wyaaba Beds and equivalents, is Miocene to early Pliocene; the third, the Yam Creek Beds and equivalents, is of Pliocene age; the youngest began accumulating in the late Pliocene and is still being deposited. The total thickness of the four sets is about 400 m; they occupy a relatively small part of the present Karumba structural Basin.