Thangoo No. lA well was drilled as a result of mechanical difficulties encountered at the drilled depth of 3 ,475 feet in Thangoo No. 1 well which were insurmountable and prevented further operations on this well. Total loss of circulation at 3,475 feet in Thangoo No. 1 well resulted in unexpected total collapse of the hole below the 10 3/4" casing in a section of friable sandstone and conglomerate (Grant Formation). In Thangoo No. lA well these formations were cased off. A lost circulation zone was tested for potential hydrocarbon production and found to contain water only. The well was drilled to 5,429 feet into basement rocks (programmed depth 4,500 feet). Excellent hole control was maintained to total depth by drilling below the 16" conductor shoe with high pH, low shear and waterloss, freshwater mud. The 1,366 feet of Mesozoic and 1,377 feet of Permian section in Thangoo No. lA closely resemble that of Thangoo No. 1. The Ordovician section is 2,318 feet thick, consisting of 695 feet of Goldwyer Formation (new name) and 1,623 feet of Thangoo Limestone (amended name). Basement, consisting of Precambrian phyllite , was encountered at 5,100 feet in Thangoo No. lA. Traces of oil were observed throughout the Ordovician section. Oil shows are confined predominantly to vuggy veins of coarse crystalline dolomite. A minor show was also observed in the sandstone of the basal unit of the Thangoo Limestone. A porous zone within the Thangoo Limestone, causing some lost circulation, appeared at about 3,670 feet in Thangoo No. lA. A formation test of this zone recovered only brackish water (11,999 ppm. total salts) with no signs of oil or gas. It is possible that the small shows of oil in the Thangoo Limestone are retained by the impervious Goldwyer Formation, as no shows were present in the Roebuck Bay and Dampier Downs wells, where porous Permian rocks directly overlie the Thangoo Limestone. The correlation of the sections of the Thangoo Limestone in all the exploratory wells on the Broome Platform indicates that the Thangoo No. lA well occupies a low structural position. Consequently the objectives of testing the structure in the Ordovician and Permian Grant Formation were not achieved. The chances of finding commercial oil accumulations in the Ordovician section of the South Canning Basin in the vicinity of Thangoo Nos. 1 and lA are very small at this time, because of the low source rock potential and flushing by meteoric waters of the Thangoo Limestone, the lack of porosity in the Goldwyer Formation, and the difficulties experienced in resolVing the structure of the Ordovician with present seismic methods.

During 1950-51 pendulum gravity observations were made at 59 stations throughout Australia using invar pendulums on loan from the Department of Geodesy at Cambridge University. A national gravity base station was established at Melbourne. Subsequent comparisons with gravity meter ties suggest that the pendulum value is about 2 mgal. low. The standard errors of the gravity differences from Melbourne to the other stations have been estimated from internal consistency of the pendulum observations and from comparison with gravity meter measurements; the mean standard error is about 0.6 mgal. A small systematic difference from gravity meter values is assumed to be caused by the effect of the earth's magnetic field on the pendulums; after correction for this, the results agree fairly well with the American calibration system. Free air, Bouguer and isostatic anomalies have been calculated for all stations. The isostatic anomalies are for both Airy-Heiskanen and Pratt-Hayford hypotheses, and for four different assumed crustal thicknesses in each case. The isostatic and Bouguer anomalies are predominantly negative. A degree of isostatic compensation is present, but some large anomalous areas are uncompensated. The pendulum survey forms a basic network to which past and future gravity surveys can be referred.

The original aim of this study was to investigate some of the early Palaeozoic Bryozoa of Australia so as to study the development of skeletal structures in the zoaria and the significance of distribution of species in the different stratigraphic successions. It was found that areas with abundant bryozoan faunas were not readily located; in many areas such as the Yass-Taemas and Tamworth districts, New South Wales, where Silurian and Devonian marine faunas are abundant, Bryozoa were poorly represented. Thus the work became an investigation of areas where Bryozoa were located. The Middle and Upper Ordovician exposures in parts of central-western New South Wales and the Middle and Upper Devonian sequence of the Fitzroy Basin (collected by the field parties of the Bureau of Mineral Resources) contained abundant bryozoan faunas at certain horizons; but they were not distributed continuously through any considerable thickness of succession. Many samples from which Bryozoa are described in the text are isolated occurrences from which two, sometimes three, species have been collected.

Between February and April 1961 the Bureau of Mineral Resources, Geology and Geophysics made a seismic survey in the Rosedale area of the Latrobe Valley, partly at the request of the State Electricity Commission of Victoria to provide more information about the brown coal measures in this area, and partly in order to test the Bureau's latest seismic recording equipment. One traverse, combining both reflection and refraction profiling techniques, was run south from the A.P.M. No.1 bore at Rosedale as far as Merrimans Creek, and a second traverse was run west from the bore as far as Toongabbie. Results show that the maximum thickness of the Tertiary sequence is about 3000 ft and that it thins gradually to 1000 ft at Toongabbie and rapidly to about 750 ft on the Baragwanath Anticline. It is shown that early Tertiary deposits were laid over the whole area but have been uplifted and partly eroded in late Tertiary or post-Tertiary times in the Toongabbie and Baragwanath areas, but the main syncline sank and accumulated thick Tertiary sediments. Results show alao that on the northern flank of the Baragwanath Anticline where crossed by the seismic lines the Tertiary and Jurassic sediments are steeply folded but not necessarily faulted. No positive information was obtained below 4500 ft but long refraction shots suggest that a high-velocity basement does not exist at a depth less than 12,000 ft.

Legacy product - no abstract available

The Canning Basin is the largest sedimentary basin in Western Australia, and the second largest basin in Australia. Excluding the seaward extension of the basin on the Rowley Shelf, and the southern part of the basin, south of Lat. 24° S, which are unknown, its area is 175,000 square miles, roughly the size of Spain. The sediments overlie a Precambrian basement, which in most areas consists of crystalline rock (gneiss, schist), and in the north-eastern part of unaltered sedimentary rocks. The Bureau started field work in the Canning Basin in 1947 and continued every year up to 1958. This work was carried out by geological parties equipped with land vehicles (1947-56) and with a helicopter (1957), by seismic and gravity parties, by an airborne magnetic party, and by a stratigraphical drilling party (1955-58). All work was based on air photographs, at a scale of 1:50,000, prepared by the R.A.A.F. This bulletin incorporates the results of all these surveys. The main published material is: Traves, Casey, & Wells (1957),* Guppy, Lindner, Rattigan, & Casey (1958), and Brunnschweiler (1954 and 1957). Geophysical work is described in unpublished records. Fossils collected by Bureau parties in the Fitzroy Basin have been the subjects of several monographs, which have been published by the Bureau. The first study of plant fossils from the Canning Basin is by White (Appendix 6). 4-mile geological series maps and explanatory notes have been published for Derby, Lennard River, Mount Anderson, Noonkanbah, Yarrie, Anketell, Paterson Range, and Tabletop; and maps and explanatory notes of Mount Bannerman, Billiluna, Lucas, Cornish, and Stansmore will be published shortly. Other major reports on the area are included in McWhae, Playford, Lindner, Glenister, & Balme (1958), Reeves (1951), and the numerous papers published by Teichert (1941, 1947, 1949, and 1950). The first attempt at compiling a geology of the Canning Basin was made by Reeves (1949, unpubl.). Photographic cover extends to 24° S, and the examination of the basin south of 24° S is postponed until air photographs are prepared. This Bulletin thus deals with the (greater) part of the Canning Basin that lies north of 24° S.

A geological reconaissance in the Nassau Range, West New Guinea

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These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.