Three samples of limestone were collected during a geological survey of the Rigo area. One sample is of Upper Cretaceous age and the others of Lower Middle Miocene age. The samples were submitted for micropalaeontological examination. The results of this examination are described here.

The Palaeozoic rocks of the Bonaparte Basin outcrop at the head and along the western side of Joseph Bonaparte Gulf and extend across the border between Western Australia and the Northern Territory. The Bonaparte Basin is the least known Palaeozoic basin in Australia, due partly to the remoteness of the area and the discouraging results of early coal explorations, and partly to the fact that the stratigraphical extent of the Palaeozoic sequence was only discovered in the last ten years. The Palaeozoic sequence so far established includes Cambrian, Ordovician, Devonian, Carboniferous and Permian sediments which rest on a pre-Cambrian basement and which are overlain in places by a mantle of Lower Cretaceous sediments. The authors intend in this paper to give an account of Carboniferous and Permian sediments of the Basin, as far as present knowledge permits, with briefer mention of the Lower Palaeozoic and Mesozoic sediments of the area.

The material described in this report was collected and forwarded for examination by Mr. M.R. Banks of the Geology Department, University of Tasmania. The report comprises notes on the lithology, fossil content, state of preservation, and correlation, of the samples.

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.

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.

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 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.

A small collection of rock samples containing Gondwana type fossil plants from three localities near Collinsville is discussed in this report. All assemblages - although with some conspicuous differences - show the characteristic Permian Glossopteris Flora. On the determination of the representatives of this flora alone, however, it cannot be said to which particular horizon within the Permian Bowen Series the samples from Collinsville belong. Modern statistical methods are suggested.

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.