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  • The Proterozoic Warramunga Group, as previously mapped around Tennant Creek, is shown to consist of two sequences separated by a major angular unconformity. The older sequence, which is tightly folded and cleaved, hosts the gold-copper-ironstone lodes near Tennant Creek. The younger sequence, exposed north of Tennant Creek, is correlated with the lower Hatches Creek Group south of Tennant Creek. It is overlain conformably by the Tomkinson Creek beds, which are correlated with the middle and upper Hatches Creek Group. The Rising Sun Conglomerate, southeast of Tennant Creek, is a composite unit, consisting of Hatches Creek Group equivalents and unconformably overlying Cambrian rocks.

  • 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.

  • Changes in microbial diversity and population structure occur as a result of increased nutrient loads and knowledge of microbial community composition may be a useful tool for assessing water quality in coastal ecosystems. However, the ability to understand how microbial communities and individual species respond to increased nutrient loads is limited by the paucity of community-level microbial data. The microbial community composition in the water column and sediments was measured across tropical tidal creeks and the relationship with increased nutrient loads assessed by comparing sewage-impacted and non-impacted sites. Diversity-function relationships were examined with a focus on denitrification and the presence of pathogens typically associated with sewage effluent tested. Significant relationships were found between the microbial community composition and nutrient loads. Species richness, diversity and evenness in the water column all increased in response to increased nutrient loads, but there was no clear pattern in microbial community diversity in the sediments. Water column bacteria also reflected lower levels of denitrification at the sewage-impacted sites. The genetic diversity of pathogens indicated that more analysis would be required to verify their status as pathogens, and to develop tests for monitoring. This study highlights how microbial communities respond to sewage nutrients in a tropical estuary. Estuarine, Coastal and Shelf Science

  • This document is a professional opinion, presenting an assessment of the macrofossils present in well CKAD0001, located in the Northern Territory in the Georgina Basin.

  • The ca. 1.4 Ga Roper Group of northern Australia comprises the sedimentary fill of one of the most extensive Precambrian hydrocarbon-bearing basins preserved in the geological record. It is interpreted to have been deposited in a large epeiric sea known as the Roper Seaway. This study presents hydrocarbon biomarkers, high-resolution trace element redox geochemistry and neodymium isotopes of immature to mature black shales to understand the microbial diversity and palaeo-environment of the Roper Seaway.

  • 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.

  • An analysis of the gravity field in two largely Precambrian metamorphic rock areas of Australia, one in the southwestern and the other in the central part, indicates that the regional Bouguer anomalies may be explained by models of the crust and upper mantle consistent with the other geophysical and geological observations. In the southwestern part, the longer wavelength component of the anomalies is consistent with a crust which has been determined by seismic measurements to be greater than normal in thickness and density in the west owing to the presence of a high-velocity basal layer that thins out eastwards. The shorter wave-length components show excellent correlation with the near-surface geology. In central Australia, where no comparable seismic measurements have been made, the Bouguer anomaly field, which is dominated by large amplitude (up to 150 mGal) and long wavelength (about 150 to 200 km) components, is interpreted in terms of thickness and structure of a two-layer crust. The derived crustal model is based on the concept of folding and faulting that involves the entire crust and upper mantIe, and is compatible with the broad aspects of surface geology and structure. The crustal upwarps in the model, with the intermediate and Mohorovicic discontinuities at depths as shallow as 15 and 27 km, are associated with the Arunta and Musgrave Blocks, where deep crustal rocks are exposed against large thrust faults. The crustal downwarps, with the discontinuities as deep as 31 and 43 km, are associated with basins containing substantial thicknesses of sediments. Depths to these discontinuities are in agreement with those estimated from the only two isolated deep seismic reflection probes in the basin areas.

  • 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.