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.

The presence of bauxite on one of the Wessel Islands was established in 1949 when specimens of laterite collected from various parts of the Arnhem Land coast were analysed. In October, 1951, the writer spent two days on Marchinbar Island and examined several small laterite residuals and part of one large deposit. The characteristics and distribution of the laterite are discussed in this report.

No abstract available

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.

The samples from Margaret Bay were collected by H.B. Owen during a recent visit to the northern coast of Australia. The collection was made with the hope that microfossils may be found in the rocks which were collected from a twenty foot section exposed at Margaret Bay. The results of the micropalaeontological examination are discussed herein.

Gravimetric and magnetic investigations have been carried out by the Bureau during October and November 1950 in order to find favourable locations for artesian water bores on lease No. 5893, known as Janina and situated in Barrona County. The geophysical survey was requested because two bores recently drilled on the lease failed to produce artesian water, although artesian water bores previously completed in the area adjacent to Janina lease proved the existence of certain aquifers yielding sufficient quantities of good water. Results of the geophysical fieldwork as correlated with data obtained from boring indicated a gentle uplift of basement rocks and water bearing strata, trending from NE to SW and occupying more or less all of the center part of Janina lease. No indications could be derived however from geophysical data as to a relatively steep uplift of basement rocks in the vicinity of bore No. 8153. Hard strata of sandrock and quartzite encountered by this bore at approximately 470 to 480 feet therefore must be classified as probably being of local character. Further drilling operations for suitable water supply naturally should avoid the aforementioned structural high, which is apparent from both boring data and gravitational work.

Gravity observations were made at quarter-mile intervals along the road that joins Bullara and Giralia homesteads. This road crosses the northern end of the Giralia anticline normal to its axis. A seismic reflection profile, which is described in B.M.R. Record 1951 No. 62, has also been run along this road and it is possible to compare the gravity results with the seismic. Gravity station elevations were determined with an accuracy of within 0.1 of a foot and the gravity observations have been reduced to Bouguer anomalies using an elevation correction factor of 0.062 milligals per foot. The results are shown in the form of a profile on the accompanying plate. The surface profile is also plotted and the positions of some of the seismic shot points are shown alongside the gravity station numbers. These results are discussed in this report.

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.

Towards the end of 1950, the deep bore which the Shell Development Company was drilling to test for oil on the Morella structure, 35 miles south of Rolleston, entered andesite at approximately 4000 ft. After boring about 200 ft into the andesite, the Company decided to abandon the hole. A new site for a test bore was selected on the Comet anticlinal structure, 60 miles north of Rolleston. Before proceeding with this new test, evidence was needed to ensure that neither a shallow basement nor volcanic rocks existed under this structure. The Bureau was therefore asked to shoot a refraction traverse over the anticline, in order to determine if basement rocks were likely to be present at a shallow depth. As a result the Bureau sent a seismic party to the area during January 1951. Fairly definite evidence was obtained of basement velocities occurring at a depth of less than 3000 ft, and after discussions, a decision was made not to proceed with the drilling of the Comet structure. The results have now been investigated in detail and are presented in this report.

A number of fossils were sent in for examination by the Director of Mines, Tasmania. The results of the examination are recorded in this report. Two different horizons are represented.