Wells Limestone, situated 8 miles from Canberra in A.C.T., is a lens of massive limestone in a formation largely consisting of shales of Silurian age. The gently undulating topography and the low relief of the area of outcrop itself do not provide an attractive quarry site, although the stone seems very suitable for use as aggregate. Soil interpretation from shallow bores indicate considerable extensions of the deposit beyond the outcrop. 'Indicated' and 'inferred' reserves of limestone [have] been calculated, although further proving of reserves should be done before it is decided to establish a crushing plant at the deposit.

In the various methods of geophysical prospecting, sensitive instruments are used on or near the surface of the earth to measure effects which arise from differences between the physical properties of rocks, ores and minerals. The analysis and interpretation of these measurements permit conclusions to be drawn concerning the sub-surface geology and the presence or absence of orebodies, coal seams, and the like, or of structures likely to be favourable to the occurrence of oil, etc. The principal physical properties of rocks which are useful in geophysical prospecting are density, elasticity, electrical conductivity, radio-conductivity and magnetic susceptibility. Aeromagnetic survey methods, their present use, and results of such surveys, are discussed in this report.

The writer spent the period May 31st to June 4th, 1952, with geological parties lead by K.A. Townley and J.F. Ivanac respectively in the Mt. Isa District, Queensland. At this time E.K. Carter had carried out one week's mapping in the south of Mt. Isa township, and had traced the Mt. Isa shale and dolomitic shale for about 12 miles south of the mine. He had shown that the Templeton granite was concordant and that it was younger in age than the Mt. Isa sediments. The writer, after considering the work carried out by E.K. Carter and a study of the photographs of the region and of the geology of Mt. Isa Mines, came to the conclusions listed herein. Observations and recommendations are discussed.

The Australian Antarctic Expedition 1911-14 established four absolute magnetic stations, namely Stations A, B, C and D. Two subsequent stations, Stations E and F, came into operation in 1950 and 1952 respectively. Because absolute magnetic observations had been made at different stations is was essential that the differences in the magnetic elements between the various stations be determined so that all data could be reduced to a common point. The observations were carried out during the period 31st March to 6th April 1952, whilst the Australian National Antarctic Research Expeditions relief operations were in progress.

The area investigated lies on the outskirts of Kotara, a suburb in the S.W. of Newcastle. The coal of interest is in the Burwood Seam. Drilling, field work, and surveying were carried out in the area. These operations are described in this report. Drilling results are discussed.

In the search for deposits of radioactive minerals in Australia the area of the Barrier Ranges appears especially worthy of investigation on geological grounds because it is composed of highly mineralised pre-Cambrian rocks. Mines in this area comprise the major producing mines along the main Broken Hill lode, one developed mine of less importance (the Pinnacles), and a number of small silver, lead and copper mines scattered over the surrounding district. The present report deals with the results of a reconnaissance radio-active survey performed by the Geophysical Section of the Bureau during July and August, 1950. The work was confined to the smaller mines, attention being directed, in the first instance to the mines from which radio-active museum specimens were stated to have come. At each mine the following tests were performed: tests on dumps and residues to discover whether any quantity of stone carrying a significant content of radio-active minerals had been broken during mining operations, tests on accessible exposed faces, and tests on rocks surrounding the mines. The tests were made with portable Geiger-Mueller rate-meters. Readings taken are quoted as multiples of background count, which has been considered as a constant characteristic of the instruments, rather than as the general reading obtained on country rock in the area. In most areas these methods of defining background would lead to the same result. As mentioned later, however, in the Broken Hill area this is not the case. Generally, the schists and gneisses on this field are definitely radio-active, and a true background reading, indicative of the complete absence of radio-active minerals, is obtained only on basic rocks. A reconnaissance survey was also made over the Euriowie tin field. Tests were also made around felspar quarries at Egebeck.

For the evaluation of the petroleum prospects of a sedimentary basin, the following factors are generally considered. Lithology, mode of deposition, thickness of the sediments contained in the basin, source and reservoir rocks. Facies of the sediments, changes in facies and the trends of such facies changes. Relationship of the various formations to each other - conformity, disconformity, unconformity, regressive and transgressive overlap, erosional gaps and their significance structurally and for accumulation. Direct or indirect evidence for the presence of oil - seepages, traces or showings of bitumen, oil and/or gas existing bores, bituminous character of some of the stratigraphic members. Tectonics - folding (single phase, multiple phase), faulting, tectonic history and its bearing on migration and accumulation of oil. Types of tectonic traps, and stratigraphic traps in relation to folding and faulting (sandy facies near basement uplift, reef formation on crests of rising anticlines, sandy facies in connection with ancient fault lines). Some of these criteria can be applied to the North-West and the Fitzroy Basins, but it is realized that the information available is not complete enough yet to fully discuss all aspects involved. On the other hand it is felt that, at this stage, a brief review of the results already obtained can greatly assist in an outline of a future programme. It will be seen that much emphasis is laid on geophysical work i.e. gravity investigations for the regional aspect of the problem - the configuration of the basins - and seismic investigations of structures which are selected for deep testing. In our opinion the results obtained so far in the North-West Basin, by both types of geophysical work, have clearly demonstrated the soundness of this way of approach

A brief geological examination of this deposit was made by the writer and D.N. Smith between 18th and 20th June, 1952. The deposit had been previously examined in 1951 by J. Daly of the Geophysical Section, Bureau of Mineral Resources, and by J.C. Lloyd of the N.S.W. Mines Department and the results of their investigation were available for reference. The radioactive area examined during the present investigation was an area of about 1/4 square mile of the volcanic flow in the north-eastern corner of portion 39. Samples of the quartz veinlets and of the volcanic rocks were collected, and tests carried out with the Laboratory Geiger counter in Canberra indicate that both are radioactive and that the radioactivity is slightly greater in the sample from the quartz veinlets.

The distribution of marine Tertiary rocks in Australia is restricted to the western and southern coastal areas of the continent. The rocks represented are of Paleocene, Eocene, Miocene and Pliocene ages. Considerable material has been collected in stratigraphic sequence from many Tertiary localities in recent years and the detailed examination of the foraminiferal content of the rocks has yielded many startling discoveries.

The sample of diatomite submitted for micro-examination came from a low bed on Beach Range at 1,110 feet above sea-level. The results of the examination are described herein.