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  • This Bulletin presents the results of a geological reconnaissance of the northwest Australian continental shelf by the Bureau of Mineral Resources carried out during two 3-month cruises, one in late 1967 and the second in late 1968. In compilation of the results some use has also been made of the shallow seismic reflection profiles and echograms collected during a marine geophysical survey of the Northwest Shelf by Ray Geophysical Division of Mandrel Industries Inc. under contract to the BMR in 1968. The other main sources of data used are the published and unpublished soundings compiled by the RAN Hydrographic Office, and the sea-bed sediment notations on Australian and British Admiralty Charts. The brief description of the offshore structural framework and Phanerozoic sedimentation is almost entirely based on the subsidized petroleum exploration work of BOC of Australia Ltd and associated companies; it does not include results obtained after 1971. The region surveyed extends from Barrow Island in the south to beyond Scott Reef, a distance of 1200 km (Fig. 1). It covers the Rowley Shelf and the southern part of the Sahul Shelf, as defined by Fairbridge (1953); in popular usage all this wide area is now referred to as the Northwest Shelf, and this term is preferred here. The basic objectives of the survey were to describe the sediments of the continental shelf and upper slope and to map their distribution, and to elucidate the late Cainozoic geological history of the continental margin from the study of surface morphology and shallow structures. The Northwest Shelf was chosen because of its position on the west side of the continent, and because the limited data available on ocean water chemistry and circulation patterns indicated that some potential for deposits of phosphate existed. Although sediments enriched with phosphorus were encountered locally, no material approaching economic grade was recovered.

  • A brief synopsis of the evidence from the Carboniferous marine faunas of Australia has been used to draw a correlation chart for the Carboniferous System in the continent. The Lower Carboniferous faunal sequence of the intracratonic basins of Western Australia is represented by the conodont and brachiopod zones established for the Bonaparte Gulf Basin. These are dated mainly in terms of biostratigraphic scales based on conodonts, foraminifers, and brachiopods established in the Lower Carboniferous of Britain and Belgium, i.e., mainly the Kohlenkalk facies. The Carboniferous brachiopod zones of the New England GeosyncIine, recognizable only in eastern Australia, are dated in terms of the ammonoid and conodont zones of the German Lower Carboniferous, i.e., the Kulm facies. Hence, in so far as it is possible to correlate the Kulm with the Kohlenkalk facies in western Europe, it is possible to make generalized correlations throughout the marine Carboniferous of the Australian continent. Correlation of terrestrial sequences in Australia, and between them and those overseas, is based on plant and spore evidence. The sporadic nature of this evidence, however, renders such correlation highly tentative.

  • Three zones of retrograded crystalline basement rocks have been delineated in central Australia. One, along the southwestern margin of the Amadeus Basin, was deformed about 600 m.y. ago during the Petermann Ranges Orogeny. Two one north of the Amadeus Basin, the other north of the Ngalia Basin were deformed during the Carboniferous Alice Springs Orogeny. Each retrograded zone is highly deformed and is flanked on one side by folded and thrust sedimentary rocks and on the other by granulite and amphibolite facies rocks. The high-grade rocks appear to have resulted from several metamorphic episodes in the Precambrian. A major gravity gradient is associated with each retrograded zone; the Bouguer anomaly highs generally occur over the areas of high-grade metamorphic rocks, and the lows over the sedimentary basins and retrograded rocks. In general, the deformed and retrograded zones are moderately to gently dipping. The gravity gradients are so wide and steep that to explain them the deformed zones must pass through the crust into the mantle beneath. The crust and mantle above each deformed zone have been upthrust, bringing granulite facies rocks to the surface and producing Bouguer gravity anomaly highs over the uplifted lower crust and mantle. The deformed zones are similar to the subduction zones that may develop on the margins of continents, but there is no evidence of continental collision in central Australia when they were formed, and they are regarded rather as possible examples of intracontinental plate reactions. They may have extended right across the continent or may terminate against strike-slip (transform) faults. A possible site for such a transform fault in Western Australia is discussed, but its existence is speculative.

  • Legacy product - no abstract available

  • Legacy product - no abstract available

  • At this scale 1cm on the map represents 1km on the ground. Each map covers a minimum area of 0.5 degrees longitude by 0.5 degrees latitude or about 54 kilometres by 54 kilometres. The contour interval is 20 metres. Many maps are supplemented by hill shading. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours, localities and some administrative boundaries. Product Specifications Coverage: Australia is covered by more than 3000 x 1:100 000 scale maps, of which 1600 have been published as printed maps. Unpublished maps are available as compilations. Currency: Ranges from 1961 to 2009. Average 1997. Coordinates: Geographical and either AMG or MGA coordinates. Datum: AGD66, GDA94; AHD Projection: Universal Transverse Mercator UTM. Medium: Printed maps: Paper, flat and folded copies. Compilations: Paper or film, flat copies only.

  • Legacy product - no abstract available

  • At this scale 1cm on the map represents 1km on the ground. Each map covers a minimum area of 0.5 degrees longitude by 0.5 degrees latitude or about 54 kilometres by 54 kilometres. The contour interval is 20 metres. Many maps are supplemented by hill shading. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours, localities and some administrative boundaries. Product Specifications Coverage: Australia is covered by more than 3000 x 1:100 000 scale maps, of which 1600 have been published as printed maps. Unpublished maps are available as compilations. Currency: Ranges from 1961 to 2009. Average 1997. Coordinates: Geographical and either AMG or MGA coordinates. Datum: AGD66, GDA94; AHD Projection: Universal Transverse Mercator UTM. Medium: Printed maps: Paper, flat and folded copies. Compilations: Paper or film, flat copies only.