The area described in the report lies between latitudes 12°48' and 12°56' S., and longitudes 130°56' and 131°11'E. Most of the mapped region lies between the Stuart Highway and the North Australian Railway. The investigation of this area is still in the early stages and has consisted of general geological mapping, and detailed investigation (including drilling) of areas found to have been radioactive during airborne scintillometer surveys carried out in 1952. At Brodribb and Ella Creek superficial hematite-rich deposits have been found to be radioactive to the extent of up to ten times background, but drilling of this type of deposit at Brodribb has not yet proved the existence of payable primary ore. Further drilling is proceeding. A new discovery at Ella Creek in July this year gave high radioactivity over a length of about 300 ft. and two pits sunk to a depth of 3 ft. of this line have shown counts of 5,000 per minute and 10,000 per minute respectively. The field geologists recommend further testing here. In the Frazer area, laterite, which contains a belt of radioactivity up to eight times background, is known to exist, but, apart from limited trenching, has not yet been adequately tested.

Six wax-sealed samples of cores were received with a request that they be tested for porosity, permeability and oil and water content. Testing was carried out by Messrs. N.V.H. Hoyling and H.S. Taylor-Rogers at the Newcastle Technical College - to the Principal and Staff of which institution grateful acknowledgment of their co-operation and utilization of their apparatus and laboratory space is made.

At the request of the Tasmanian Hydro-Electric Commission a geophysical survey was carried out along a tunnel line at Trevallyn, a suburb of Launceston, North Eastern Tasmania. The excavation of the Trevallyn tunnel is part of the Hydro-Electric Trevallyn Power Development project to utilise the water of the South Esk river for generation of electric power. The construction works are already well advanced. A dam is being built on the river at the Second Basin. Water from the catchment will be diverted through a tunnel two miles long to a power station situated at sea level on the Tamar River. A locality map is given in Plate 1. Three geophysical exploration methods, electrical, seismic and gravitational, were used to locate deeply weathered and fractured zones in the dolerite bedrock, through which the tunnel is being driven.

The stratigraphy and structure of an area in the Carnarvon sedimentary basin covered by the Williambury and Moogooree one mile sheets, is described. Resting unconformably on a Pre-Cambrian basement of schists gneisses and granites, are Devonian marine sediments 4750 feet thick, followed conformably by Carboniferous approximately 2150 feet thick; these are separated from the overlying Permian more than 8000 feet thick, by a possible hiatus. The Cretaceous System is represented by about 40 feet of siltstone lying unconformably on the Palaeozoic rocks. Marine Tertiary arenaceous deposits are widespread and have a maximum thickness of 80 feet; they are not seen in contact with the Cretaceous rocks. The whole area has been subjected, in Tertiary time, to lateritisation, the most prominent feature of which is the presence of a silicified cap ranging in thickness from a few feet to 30 feet. In one place a post-laterite deposit of 12 feet of probably fresh-water limestone has been observed. An account is given of the structural geology, geological history, and physiography of the region.

The features of the single-point resistance log, obtained in A.A.O. No. 2 Bore, Roma, are described. Single-point resistance, self-potential and geological logs of the lower section of the boreholes are shown. The results indicate that electrical logging can be effectively used for correlation problems and that salt water sands in the reservoir rocks can be detected with reasonable certainty.

The Fitzroy Basin is situated south-east of Derby in the Kimberley Division of Western Australia. Results are given of a semi-detailed gravity survey which was made of the portion of the basin between longitudes 123°40' and 124°30' and latitudes 18°05' and 18°40'. The survey disclosed a large basin structure at least 7,000-8,000 feet deep and a few minor anomalies which may prove important. It is not known whether the higher density formation at 7,000-8,000 feet depth in the basin represents Pre-Cambrian basement or sediments of Devonian or Ordovician age. The position of, and displacement on, the Fenton Fault system were indicated. A detailed gravity survey of the Nerrima structure confirmed the existence of faults which had been mapped by the Bureau's geological and seismic parties, but was unable to determine the depths to which these faults penetrated. Seismic refraction work and test drilling are recommended south of the Fenton Fault, between Barnes' Flow and Mt. James, to disclose the nature of the higher density formation. Recommendations are also made for an extension of the detailed gravity survey to areas in which anomalies were revealed by the semi-detailed survey.

This report is concerned with the bryozoan faunas of the Nura Nura limestone and the Noonkanbah series. The bryozoan faunas from individual localities and the distribution of species occurring in areas other than the Kimberley district are listed. Other aspects of the faunas are discussed. This discussion includes a general consideration of the facies, a description of the faunas of the Nura Nura Limestone, and a comparison with other Permian faunas. A supplementary list of the bryozoan faunas of localities in the Noonkanbah series represented by the Teichert's specimens is included.

This statement has been prepared as a supplement to Summary Report No. 27 - Aluminium and Bauxite - which was issued in 1946. Since that year testing of deposits in Tasmania has been completed and new discoveries of commercial bauxite have been made in northern New South Wales and the Northern Territory. Further exploration in South Gippsland has resulted in minor additions to the proved reserves of Victoria, and the presence of bauxite has been reported in Papua and New Guinea. Exploration of deposits of bauxite on the north coast of the Northern Territory is not complete but sufficient accessible reserves have been proved to change the formerly unfavourable outlook for the aluminium industry now being established in Australia. Re-examination of the formerly known deposits has necessitated recalculation of the stated reserves, and has generally resulted in a reduction of the earlier estimates, but on the other hand a substantial increase has been made for the Tamborine Mountain deposits in Queensland. South Gippsland tonnages have been recalculated and expressed as dry ore so as to be consistent with the statements for other States. Tonnages throughout are long tons (2240 pounds) of dry ore. In the following tables proved reserves are those which have been systematically tested by pits or bores regularly spaced at intervals of not more than 400 feet, and in many cases only 100 feet. Indicated reserves have been tested by more widely or irregularly spaced holes.

In the search for deposits of radio-active minerals the Bureau has used scintillometer equipment mounted in a D.C.3 aircraft with considerable success in suitable country. In order to investigate the possibility of extending the application of this type of survey to mountainous country, over which the D.C.3 could not be used, tests of similar equipment mounted in a helicopter have been made over three areas in New South Wales. The areas selected were at Carcoar, Tenterfield and Broken Hill. The results of the tests indicate that a scintillometer mounted in a helicopter can be successfully used in almost any type of country. However, in areas of low relief, the D.C.3 aircraft is preferable, owing to its greater speed and to the fact that it can carry auxiliary equipment by means of which its position at any time can be accurately fixed. The helicopter will not give the rapid and complete routine coverage of large areas that is given by the D.C.3. In rugged or mountainous country where the larger aircraft cannot be used the helicopter offers great advantages over other methods of prospecting for radio-active deposits. For this work it is best operated by following flight lines related to easily identifiable map features.

This report contains the results of a seismic survey on the Nerrima Dome, a major structure within the Fitzroy Basin and near its south-western boundary. The dome is situated near the Fitzroy River about 100 miles south-east of Derby in the West Kimberley district of Western Australia. The Nerrima Dome has been mapped at the surface in Permian sediments and is a complex structure. It was desired to determine if the dome existed at depth and, if not, the structure at depth, with a view to locating a site for a deep drilling test. The target beds for such a test are Devonian and/or Ordovician sediments over which the Permian sediments are believed to lie unconformably. Reflection methods were tried and proved unsuccessful and the survey was carried out using refraction methods. Although the structure underlying the dome has not been clearly shown, the refraction method has indicated that it is complex and does not conform with the domal structure at the surface. There appears to be a major unconformity at comparatively shallow depth (2000 ft). The deep structure (7000 ft) although apparently less complex than that immediately below the unconformity, also bears no obvious relation to structure at surface. The results so far obtained are reasonably conclusive in showing that no simple dome-like structure of large magnitude exists under the Nerrima Dome.