The main sedimentary basins of Western Australia are arranged peripherally to the pre-Cambrian shield which forms the greater part of the state. In 1948, the Commonwealth Bureau of Mineral Resources, Geology and Geophysics, by arrangement with the government of Western Australia, commenced detailed geological reconnaissance of the Fitzroy and North-West Basins. In 1948 and 1949, the R.A.A.F. carried out a programme of aerial photography of these basins and this air-photo survey has since been used as the basis for mapping in the field. In the course of this work several discoveries have been made and as only brief mention of them has been made elsewhere they are included in this summary. The main areas of Palaeozoic sedimentation in Western Australia at present known are the Ord Basin in the far north-east, the Fitzroy Basin, the North-West Basin stretching from Onslow to the Murchison River, and the Irwin-Perth Basin stretching from Geraldton to Busselton.

During an inspection of limestone deposits at White Rocks on 2/11/50, samples of weathered granite were collected from a quarry on the eastern side of the Queanbeyan-Cooma road, about 150 yards south of the two-mile peg. This quarry is in the Queanbeyan Clay Deposit described by W.G. Woolnough in departmental reports dated 17/2/28 and 20/6/28. If the rock can be economically crushed and worked, it may be suitable for the production of sewer-pipes and other impervious ware. The samples, reserves, and suitable uses for the granite are described in this report.

The areas included in the geophysical survey, namely the Laloki, Moresby-King and Dubuna leases, are among those held by Mandated Alluvials N.L., and lie in the Astrolabe Mineral Field. The positions of the leases held by the Company are shown in Plate G73-1. Laloki, the main producer of copper, is situated 20 miles by road from Port Moresby, near the junction of Sapphire Creek with the Laloki River. The Bureau was requested by Mandated Alluvials to carry out a geophysical survey in the vicinity of the known deposits and in adjacent areas. Both Laloki and Moresby-King mines has been in production up to the time when the war in New Guinea caused a suspension of operations. During the war the mine workings and much of the plant were completely destroyed. When consideration was given to the best method of reopening the mines it was decided that, if a large enough tonnage or ore could be proved sufficiently close to the surface, it would be most profitable to continue open-cut mining, and possibly install a flotation concentrator to avoid the troubles that had always accompanied smelting. The aim of the geophysical survey was, therefore, to locate a body of ore large enough to justify the adoption of these mining and treatment methods.

The area investigated, now commonly known as the Daly River Area, is situated on the north-eastern bank of the river, about 35 miles from the river mouth, and approximately 80 miles south of Darwin. The present survey was made in July 1950, in conjunction with work being done by the Bureau at Rum Jungle, and was a general investigation for possible radioactivity in the district. Although no radioactivity of interest was detected, it is considered desirable that the results of the investigation should be recorded. The geology of the area, field work, and results are described in this report.

The samples described in this report, which were submitted by the Director for petrographical examination, come from the Janjukian and Anglesean deposits between Torquay and Airey's Inlet. All sedimentary rocks from the area have been named according to the classification drawn up by M.A. Condon. The results of a rough chemical analysis made in 1947 on a sample of supposed jarosite are given, and a note on the occurrence and possible origin of the glauconite found in many of the samples is appended.

This report describes the results of a micropalaeontological examination of rock samples from the lower Minilya area.

The following is a summarised account of an investigation into the heavy mineral content of thee bores (Nos. 2, 3, and 4), put down by the Roma Blocks Oil Company. The positions of the bores and a short account of the geology of the area are given, together with results of the work to date, and an evaluation of the prospects of correlation by petrological means.

This report describes the results of a micropalaeontological examination of samples, collected from bores nos. Z.18, T.29, HH.57, and PP.59, in the Moorlands Coalfields.

A sample of diatomite was submitted for palaeontological examination. The results are of the examination are recorded in this report.

This is the second progress report of the coal drilling programme near Ashford in the Parishes of Macdonald and Myall, County of Arrawatta. The first report (Record 1949/106) covered the drilling of D.D.H's 1-5. Drilling was continued to test the coal measures lying between old Ashford Colliery and the Severn River. Five more holes were drilled through the coal seam, north of No. 2 D.D.H. An account of the drilling work is set down in this report, together with a description of local geology, and estimates of the coal reserves in the field.