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.

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The Ordovician age of the limestone at the Belubula River was recognized by the present writer from fossils collected by Mr. N.C. Stevens, University of Sydney. Thought, in the opinion of A.A. Opik, the first collection examined was completely convincing, Mr. Stevens approached the Chief Geologist, Dr. N.H. Fisher, early in 1951 for further support in the field. It was then decided that A.A. Opik, being responsible for the age-determination of the fossils from the Belubula River, Cliefden Caves area, would accompany Mr. Stevens on a field excursion to collect more evidence for the age of the limestones and to look for an occurrence of Silurian fossils in the same area. The results of this examination are given in this report, comprising a description of the Ordovician sequence, and a summary of the stratigraphy and correlation of the Ordovician Belubula River.

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 contains the results of brief geological investigations carried out in conjunction with the Land Research and Regional Survey Unit to provide information on land types and their distribution in the Burdekin River Valley. A geological map and sections at the horizontal scale of 4 miles to 1 inch have been compiled from air-photo interpretation controlled by widely spaced land traverses. An account of the stratigraphy is given, and palaeontological reports on the fossils collected appear as appendices.

The boring campaign carried out during 1950 by the Petroleum Technology section of the Bureau proved the existence over an area of 25 square miles in the Oaklands-Coorabin coalfield of approximately 793,000,000 tons of coal with an average calorific value of 9150 B.Th.U. per 1b. Thickness of the coal intersected in the bores ranged from 18 to 59 feet and depth to the coal from 186 to 565 feet. This report comprises detailed coal analyses, notes on the geological results, and recommendations for future boring.

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.

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.

A magnetic survey of the Kunimo creek area near Kuta in the Central Highlands of New Guinea was carried out between July 17th and July 28th, 1950. It was hoped that the survey would trace the course of the auriferous wash originally laid down in the bed of a former creek but now concealed by overburden of soil and unconsolidated volcanic ash. This report gives an account of the magnetic survey and its results.