Rurnbalara railway siding is 831 miles by rail north of Adelaide, South Australia, and 120 miles by rail south of Alice Springs, Northern Territory. The ochre deposits (Plate 1) are situated in desert country, 15-20 miles northeast of the siding. No permanent water supply has been developed in the vicinity of the mines. Numerous mesas in the district are capped by siliceous laterite (grey billy), and are composed of approximately 150 feet of horizontally-bedded, leached shales and sandstone containing numerous fossils of Lower Cretaceous age. These beds, for which the name Rumbalara Shale is proposed, rest unconformably on the eroded surface of flat-lying, current-bedded sandstones of which the age has not been determined; it is proposed that the sandstone beds be called the De Souza Sandstone. .The ochre occurs in beds 1 to 4 feet thick; the best grade consists of soft, friable, golden-yellow material, free from grit and with good paint-making properties. Throughout the deposits the ochre occurs at the same stratigraphic horizon- at the base of the Lower Cretaceous-and appears to be of sedimentary origin. Excluding 1943 and 1944, annual production during 1940-1948 averaged 500 tons; in 1943 and 1944 production was 1,345 and 1,439 tons respectively. The deposits are very extensive, but prospecting carried out to date indicates that only some of them contain ochre equal in grade to that being mined. However, although there are virtually no proved reserves, the field is probably capable of supplying Australia's requirements of yellow ochre for many years.

Legacy product - no abstract available

Field work at Rum Jungle commenced on 18th May and terminated 15th November. The greater part of the field season was spent in detailed geological and geophysical examination and testing of White's Deposit, Dyson's Find, Mt. Fitch Radioactive Area, Brown's Workings, and Brown's Extended. The results of these investigations are summarised in this report.

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.

For the purpose of obtaining further information as to favourable structural features in relation to brown coal seams within the Yallourn-Morwell-Traralgon area, a gravity survey is being carried out by the Bureau of Mineral Resources, Geology and Geophysics at the request of the State Electricity Commission of Victoria. In the following a preliminary interpretation is given of the results obtained by this survey to date. This interpretation includes a detailed correlation of the gravitational disturbances with the geological structures so far known. Practical experience to be gathered from the work so far done has been outlined.

A micropalaeontological examination was conducted on a sample of diatomite from Redesdale. The results of this examination are described here.

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.

A sample of limestone from Bougainville was submitted for micropalaeontological examination. The results of this examination are described here.

The purpose of the investigation was to determine the degree of uniformity of the earth's magnetic field over the existing and the alternate compass swinging sites for ground swinging of aircraft. Field work was carried out on 30/1/51 and 5/2/51. Instruments used were the Vertical Force Variometer and the Wingfield Compass. The report gives an account of the field work and the results of the survey.

The Government of India invited the Australian Government to send a representative to the celebration of the Centenary of the Geological Survey of India during January 1951. The first meeting of the Pan-Indian Ocean Science Congress was scheduled for the first week in January, 1951 so the Bureau of Mineral Resources, Geology and Geophysics selected M.A. Condon to attend the Science Congress and the Centenary Celebrations because his work in the North-West Basin of Western Australia would be of some interest to geologists working around the Indian Ocean. This report comprises a detailed itinerary and geological notes on the areas visited during the course of the visit.