The oldest rocks found in this area are Pre-Cambrian and the youngest are Recent but on the whole the area is one of great stability and not many of the periods of geological time are represented. The Pre-Cambrian are found outcropping round the edge of the basin and for simplicity in field work have been divided into five divisions. These are Tennant Creek, MacArthur R., Buldiva, Helen Springs, and Barkly Downs. This report provides a field summary of geology by division.

Samples from 46 deposits of the known 76 occurrences of diatomite in Australia have been micropalaeontologically examined, and 27 genera of diatoms represented by 48 species have been identified from them. The distribution of these species in the various diatomites is given in Table II. The following tentative conclusions with regard to the suitability of Australian diatomites for filtration purposes are based on a study of the shapes and sizes of the contained diatoms,' in accordance with English and Californian experience. Extensive deposits of diatomite, which are dominated by the diatom Melosira and which are suitable for purposes other than filtration, are available in Queensland and New South W ales. Nevertheless, this type of diatomite is used successfully by Davis Gelatine (Australia) Ltd., as a filter medium. The commercial value of a diatomite as a filter aid, which depends on the amount necessary to give a perfectly clear filtrate, the speed of filtration, and the character of the press-cake and similar criteria, can only be satisfactorily determined by actual experiment. It is also necessary to establish a correlation between the characters determined by microscopic examination and actual filtration tests before a final conclusion can be stated.

A geophysical survey of the Hampton Plains areas was conducted between September and December, 1946. The geology and nature of the problem, geophysical work, and results of the survey are discussed in this report. Accompanying plans are included.

This geophysical survey was undertaken as part of a campaign by the N.S.W. Mines Department and the Commonwealth Bureau of Mineral Resources to explore the ore possibilities of the Cobar Mining Field. Tests, made in January 1947, on specimens of ore from the operating mines showed that some of the ore from the New Cobar and Chesney Mines exhibited appreciable magnetisation due to its pyrrhotite and possibly magnetite content. The survey was commenced in March, 1947 using the magnetic method only as a first method of attack. Watts Vertical Force Variometers Nos. 15887 and 16128 were used, the field work being carried out by the writers. The geology of the area, object of the survey, results, and recommendations for future drilling are discussed in this report. Two accompanying plans are included.

Collie is the only developed coalfield in Western Australia. Between June 1946 and April 1947 a comprehensive geological and geophysical survey was carried out to determine the boundary of the basin, its general configuration and the depth (thickness) of the sediments overlying the basement. The aim of the survey was to define those areas where there was sufficient thickness of sediments to enable drilling to be carried out with a reasonable expectation of proving additional reserves of coal. The geology of the area, application of the gravity method, results and interpretations, and drilling recommendations are discussed in this report.

Results of a micropalaeontological examination of samples taken from the depth of 3 feet down to 534 feet.

A geological reconnaissance was made of an area of approximately 27,000 square miles lying north and west of Katherine in the Northern Territory. The report is compiled in two parts. The first concerns general geology and includes accounts of the nomenclature, stratigraphy, structural geology, geological history, and geomorphology of the area. The second part comprises a summary of the economic geology. The mining industry, petroleum prospects, underground water, and recommendations are discussed. A table showing the mineral production figures for the Northern Territory, northern district, is appended.

A geological report on the Alexander, Halley's Comet, and Manolis' Workings mines. The production, grade, geology, mineralisation, ore reserves, and prospecting of the mines are discussed. Accompanying geological plans are included.

The geology, production history, ore grade, and ore reserves of the Northern Star Mine are discussed in this report. Four accompanying plans are included.

Bauxite deposits in the vicinity of Gelliondale were investigated. The report comprises notes on the locality, geology, volume, and nature of the bauxite deposits.