AU-TAS
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Legacy product - no abstract available
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Legacy product - no abstract available
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Legacy product - no abstract available
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Two manganese nodules having a high clay content, a low Mn:Fe ratio, and low contents of valuable metals (Ni 0.25%, Cu 0.17%, Co 0.06%) were recovered in a grab sample during a short geological cruise in HMAS Kimble in the southern Tasman Sea in May 1979. Five stations were occupied. Free-fall grabs recovered sediment or pumice from four stations; nothing was recovered from the fifth. The carbonate compensation depth in the region is about 4500 m. Reddish brown clay, but no manganese nodules, was recovered in the central southern Tasman Sea, from depths of 4900-5100 m. The nodules, together with grey calcareous mud, were obtained from a depth of 4300 m, farther to the northwest, near Gascoyne Seamount (250 n. miles SE of Sydney). The results suggest nodules with high metal values are likely to exist only in the broad and deep depression in the central southern Tasman Sea southeast of Gascoyne Seamount, where sedimentation rates are low and oxidising conditions prevail. Whether nodule fields are present or not will only be resolved by considerably more sampling.
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Product no longer exists, please refer to GeoCat #30413 for the data
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75% coverage south margin missing 22-2/K55-3/8-6 Vertical scale: 30
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In early 1987, scientists aboard R.V. Rig Seismic carried out a 29 day research cruise over the Otway Basin and the Sorell Basin of the west Tasmanian margin, to provide new geological, geochemical and heatflow data, in an area with considerable petroleum potential. Altogether, 130 sampling stations were occupied using dredges, corers, grabs and a heatflow probe. Among the rocks recovered were: Palaeozoic volcanics and metasediments; Late Cretaceous sandstones, siltstones and mudstones; early Tertiary siltstones; and late Tertiary carbonates. All samples were taken along seismic profiles, so that the results can be easily incorporated into the regional geological framework. In general, the further down the continental slope, the older the rocks. Palaeontological results indicate that there has been very considerable post-Eocene subsidence of the slope. A great variety of Quaternary sediments were recovered, and these have allowed a detailed sedimentation model to be developed. Heatflow calculations from 20 stations suggest that the present zone of thermal maturation of hydrocarbons is 2-4 km deep. Headspace gas analyses of many cores indicate that thermogenic hydrocarbons are widespread, with particularly high readings in both the eastern and the western Otway Basin and on the west Tasmanian margin. Thus, mature hydrocarbon source rocks must also be widespread.
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Between 1951 and 1959 four engineering geophysical surveys were made in the Great Lake North District of Tasmania. Gravity, magnetic, seismic, resistivity, and radiometric methods were used to investigate geological conditions and rock properties along the line proposed for tunnels and other works for a hydroelectric scheme. The surveys provided much information that was of value in both planning and construction of the scheme. This Bulletin incorporates the description of the four surveys and the results obtained by them. During the period of the geophysical surveys more diamond-drill holes were drilled by the Commission. In this Bulletin, the region surveyed will be referred to as the Great Lake North District and the separate parts as the Intake Tunnel Area, the Outlet Portal Area, the Penstock Line Area, and the Tailrace Tunnel Area.
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22-1/K55-5/1
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Legacy product - no abstract available