This report has been prepared at the request of Engineers of the Department of Works and Housing. The writer spent a day with Mr. Crotty examining the site, and another day alone studying general geological conditions relevant to the proposed scheme. The visit and its findings are outlined in this report.

As a result of abnormal rains in 1950, a considerable body of water has been impounded in Lake George, situated in New South Wales, but only 20 miles north of Canberra, Australian Capital Territory. Local reports claim a depth of water of 30 feet in the Lake and these reports have prompted the Advisory Council of the Australian Capital Territory to investigate the possibility of developing the lake as a recreational resort. As a first step in this investigation the Council has asked the Bureau of Mineral Resources, Geology and Geophysics for an opinion as to how long a considerable body of water may be retained in the lake.

The object of my trip to the United States of America was to discuss problems of micropalaeontology with various authorities in that country, to visit the palaeontological laboratories of the United States Geological Survey and National Museum, State Universities, Museums and laboratories of oil companies and to enquire into the latest techniques used in oil-field laboratories. I was also to attend the joint Annual Convention of the American Association of Petroleum Geologists, Society of Economic Palaeontologists and Mineralogists and Society of Exploratory Geophysicists at St. Louis. This report gives an account of the institutions visited by the author and the principal results of the visit.

The geophysical survey described in this report was undertaken at the request of the Snowy Mountains Authority for the purpose of investigating possible sites for the proposed Spencer's Creek dam. The area surveyed is about two miles above the junction of Spencer's Creek with the Snowy River, about six miles east of the summit of Mt. Kosciuszko, and at an average elevation of about 5,700 feet above sea level. The specific information sought by the survey comprised the following: depth and nature of the bedrock, contours of the bedrock surface, nature of the overburden, and in particular, variations in physical properties occurring either horizontally or vertically. The seismic refraction method was used in the survey. This report gives an account of the geophysical survey and its results.

The Northern Territory is an integral part of the great Australian Pre-Cambrian shield which underlies almost the whole of Western Australia and the Northern Territory, much of South Australia and portions of New South Wales and Queensland. In most parts of the Continent, Pre-Cambrian rocks were welded into a stable shield before the end of Pre-Cambrian time, and in the Northern Territory itself the structural framework was established, and most of the mineral deposits introduced by an orogeny which terminated geosynclinal sedimentation about the end of the Lower Proterozoic. This discussion of the structure of the Territory in relation to mineralization is mainly concerned with Pre-Cambrian, and in particular with Lower Proterozoic rocks. Only a broad outline of the subject is given here.

This report deals with the work done by a field party of the Geophysical Section, Bureau of Resources, on leases in the Astrolabe Mineral Field held by Mandated Alluvials N.L. The work was done in the 1950 field season from March to December and was a continuation of the work done in 1949 and described in the first progress report. The geophysical survey was conducted using the magnetic, self-potential, equipotential-line, potential-drop-ratio, and electromagnetic methods. An overview of the geophysical methods used, their results, and the local geology, is provided for each of the individual areas surveyed in the course of this work.

Attention has been directed to the cobalt workings at Carcoar as a possible source of radioactive minerals in two ways. During testing of museum specimens for radioactivity, it was found that cobalt ore from Carcoar was strongly radioactive. Also, the occurrence of uranium in the cobalt ores was reported by Mr. McKillop, formerly a land holder in the area, who submitted a copy of a report signed by Professor T.H. Laby, certifying the presence of uranium in samples examined by him, and at a later date, a sample containing an uranium mineral. A brief visit was paid to the area in 1948, and the presence of strong radioactivity on dumps was confirmed. A more extensive survey of the area was, therefore, undertaken by geophysicists during 1949-50 and 1950-51. This report gives an account of the geophysical operations carried out in the vicinity of the Carcoar cobalt workings and describes the results of these investigations.

Mount Hope, a small town in Central New South Wales, is south of and 101 miles by main road from Cobar, and 11 miles north of Matakana siding on the Sydney-Broken Hill railway line. The ores mined in the Mount Hope district have been mainly those of copper, the principal mines being the Mount Hope mine, close to the town, and the Great Central and Comet mines, three miles further south. At present, the only mine in production is the Mount Hope mine, where the leaching process is being used by the Caroline Copper Mines. At the request of North Broken Hill Ltd., geophysical surveys were carried out on two areas: the Mount Hope mine area, and the Comet Mine area. The field work was commenced in May, 1950, and occupied three months. This report gives an account of the geophysical surveys and their results.

In January, 1951, samples of radioactive minerals stated to have been collected in the Mt. Kavanagh (Cavenagh) area, Central Australia, were submitted to the Bureau by Mr. Norman Ashmore. Two radioactive minerals were present, one apparently allanite, and the other a strongly radioactive mineral of composition similar to betafite. The opportunity was taken of the presence in Alice Springs of the geophysical party destined for Rum Jungle and the geological party destined for Maranboy to make a brief inspection of the area. Two days were spent in the area. This report gives an account of the investigations and their results.

A seismic survey was carried out near Roma during 1949-50, being part of a geophysical programme to search for structures likely to be significant for oil exploration. As preparation and publication of the final report on the survey may take some time it is desired to present briefly the main results in the form of a preliminary report. The first phase of the geophysical survey work at Roma comprised gravity and magnetic surveys, the results of which were presented in Bulletin No. 18. The residual gravity pattern revealed two possible structural high closures. The object of the seismic surveys was to prove or disprove the existence of these structures, and to obtain more detail concerning them if proved.