An earlier report (Record 1950/041) has described the geophysical survey carried out early in 1950 on the Renison Bell tin field. The present report deals with the work of a second field season which commenced in November 1950 and continued until June 1951. The methods used were again the magnetic and self-potential. The 1950 survey was extended to the south and east by continuing along the Renison Bell Hill base-line a further 1000 feet south and reading stations on both sides of this base-line along traverses extending from the main quartz-porphyry dyke to the headwaters of the Montana Creek. In addition, some of the traverses were extended over the saddle between Dreadnought and Stebbins Hills as far as the Boulder tramway. The report gives an account of the survey work and its results, and provides recommendations for future testing. The geological features of the area covered by the present geophysical survey are briefly described.

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.

The present report summarises the progress in the study of Cambrian fossils from the Northern Territory and north-west Queensland. The material being studied consists of large collections made in the Barkly Tableland by members of the Bureau of Mineral Resources, and a selected set of fossils borrowed from the Australian Museum. In addition, a comparatively complete collection from the Ord River and Mt. Panton is available for comparison. This report provides an overview of the work being carried out. Brief summaries are provided of the present state of research done by A.A. Opik, and of papers planned by other authors.

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.

Four days were spent in the area, observations being severely limited, firstly by lack of knowledge, on the part of the observer, of overall topography such as could be obtained from aerial photos or viewing the area from an aircraft and secondly by the dense fog which covered the area for the greater portion of the time spent there. Captain Fox of Q.E.A. had previously informed me that during the aerial inspection made by Mr. G.A. Taylor, three areas of "burnt" ground had been observed. Mr. Jones during his stay in the area had located two of those and in addition, two more minor areas. During my stay in the area those fumarolic areas were inspected and in addition, the third area located and inspected. The three major areas shall be referred to as the lower, middle and upper fumarolic areas.

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.

This report is a detailed stratigraphical and structural study of an area of some 40 square miles south-east of Cobar together with a geological reconnaissance of an area of 500 square miles in the Cobar-Canbelego district. The purpose of these investigations was the elucidation of the general geology and the problem of ore localisation in the Cobar-Nymagee-Canbelego metalliferous province.

The Mosquito Creek Wolfram Field was visited on 6th and 7th October, 1951. This report gives a brief account of the inspection. The general geology of the area, the ore-bearing reefs, and the mining leases inspected, are described.

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.

This report covers the results of a seismic reflection traverse on a portion of the Giralia anticline which has been mapped in Mesozoic and Tertiary rocks in the North-West basin. The work constitutes a part of a general programme of investigation which the Bureau of Mineral Resources, Geology and Geophysics, has been carrying out on Permit areas held by Ampol Petroleum Ltd. in this area. The seismic traverse described herein lies along the main road joining Giralia and Bullara homesteads and crosses the northern end of the Giralia structure. Tests were made with shooting in shot holes and also by air shooting. In addition, a refraction spread was shot along the axis of the anticline. This report gives an account of this investigation. Technical matters, such as interpretation technique and the symbols used in plotting results, are briefly noted. The results of the study and subsequent conclusions are discussed.