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  • Discussion: Ollier and Taylor (1988) are correct when they write that the Kosciusko- Bega region has long been of interest to geomorphologists, They also point out that there has been debate over its geomorphic evolution since the early 1900s and, after reviewing some of this, develop a hypothesis of landscape evolution for the area. We wish to examine the data underlying their hypothesis, and comment on other aspects of their paper.

  • Lake Amadeus, a large playa in central Australia, is part of a 500 km long groundwater discharge zone, which extends from Lake Hopkins, in Western Australia, to the Finke River. In this zone, groundwater discharges and evaporates at playa surfaces over a total area of 1750 km2. Groundwater flows towards Lake Amadeus in Cainozoic sediments which overlie fractured Proterozoic bedrock. Sediments beneath the lake bed are saturated with sodium-magnesium chloride rich brine, which contains about 250 g/L total dissolved solids. The lake bed is generally dry and contains areas of heaved gypsum ground and slightly lower, flat, halite-encrusted zones which are occasionally flooded. Gypsum is actively precipitating in the capillary zone above the water-table, which is generally at a depth of 0.30-0.50 m. In Lake Amadeus and other nearby playas the total mass of salt stored is estimated as about 6000 million tonnes and this has accumulated in about 12000 years. Water-budget calculations show that groundwater recharge in the catchment of 90 000km2 is approximately 1 mm/year, which is only 0.4 per cent of the incident rainfall.

  • The regolith of the Kalgoorlie region includes saprolite in deep weathering profiles, and a range of surficial deposits, including colluvium, alluvium, and duricrusts, the distribution of which is the result of a long geological and geomorphic evolution. The generally accepted model of landscape evolution, with an old lateritised plateau being replaced by a younger plateau, is shown to be oversimplified. Features in the saprolite indicate changes in the former position of water tables. Sand plains are essentially confined to areas of granite; and red earths, to greenstone belts. Neither of these appears to have any significant aeolian component. Ferricrete is generally unconformable over various substrates: it originally formed on lower slopes, and occupies high sites in the present landscape because of repeated inversion of relief. Silcrete appears to have the same landscape relationships. In a new geomorphic chronology of the region regolith formation is treated as an integral part of the geological history since the Permian.

  • Tightly folded migmatitic rocks, intruded by 1860 Ma granite and younger felsic and mafic dykes, are exposed in a band 95km long and up to 10km wide along the western part of the Kalkadoon-Leichhardt Belt. The migmatites are considered to represent the basement underlying Proterozoic cover rocks, the oldest of which are Ma felsic extrusives (Leichhardt Volcanics) about 1860 Ma old. The migmatites include thinly banded gneiss with mainly concordant leucosomes (metasediments), non-banded gneiss with wispy leucosomes (metavolcanics), and nebulitic granitic gneiss (meta-intrusives). Metamorphism and deformation of the migmatites took place before the intrusion of a cross-cutting granite dyke dated at 1860 ± 32 Ma by U-Pb zircon. Another U-Pb zircon age, 1850 ± 16 Ma, obtained for a migmatitic metadacite, is anomalously young, although within experimental error of a preferred migmatisation age of 1860 - 1870 Ma. Uplift rates of 2-5 mm a year are implied, to account for the inferred brief interval between migmatite formation and ensuing felsic volcanism.

  • Samples from the Rudiger Point-Cape Ruge area, New Britain, are not from a conformable late Miocene-earliest Pliocene sequence, as was presumed by previous workers, but rather are of two age groups, one of general middle Miocene age, and a younger group of late Miocene age. A sample of volcanolithic sandstone, NG34B, is of late Pliocene-middle Pleistocene, Zone N.21-Zone N.22, age; this is the youngest marine sediment yet recognised in New Britain. Planktonic Zone N.18 is correlated, at least in part, with a normally magnetised interval.

  • The South Australian seismic network comprises 12 short-period, permanent stations distributed over a large area of the State. The network provides earthquake monitoring down to magnitude ML ~ 2 for most of the State, with an improved location capability of ML ~ 1 for the seismically active Adelaide Geosyncline zone. At any time the permanent network can be augmented by 13 sets of portable equipment, which include 6 microprocessor controlled, battery-powered digital event recorders built in-house. The earthquake data are analysed on a dedicated Data General computer system and graphics unit. The software is an integrated, interactive system of seismic analysis routines, covering all the data processing needs of the network, from station calibrations and updating of station data, through the determination of locations and magnitudes of local earthquakes and the needs of microearthquake survey data processing, to the retrieval and display of earthquake statistics from an archived data base. The computerised seismic data processing system has been used in the routine analysis of all local earthquakes and microearthquake surveys in South Australia since the beginning of 1978.

  • The first well-preserved bones of phyllolepid placoderms from the Devonian of central Australia are described from the Deering Hills and Waterhouse Range in the Amadeus Basin, and are compared with fragmentary remains from the Dulcie Range in the Georgina Basin . The fossil horizon in the Deering Hills occurs in strata previously mapped as part of the Mereenie Sandstone, but which clearly belongs to the Harajica Sandstone Member of the Parke Siltstone (Pertnjara Group). At this locality in the Deering Hills the entire Harajica Sandstone and underlying Deering Siltstone Members disappear along strike against the top of the Mereenie Sandstone, indicating that the formation boundary is not a simple angular unconformity as had been previously assumed. Two phyllolepid species of uncertain generic assignment appear to be represented in the Pertnjara Group. The Waterhouse Range occurrence may be a younger fossil horizon than that in the Deering Hills. A third indeterminate genus and species occurs in the upper Dulcie Sandstone in the Georgina Basin, and is associated with remains referable to Austrophyllolepis Long, 1984 and Placolepis Ritchie, 1984. These genera are otherwise only known from Frasnian strata in southeastern Australia. A provisional zonal scheme, with a suggested age range of late Givetian to late Famennian, is proposed for phyllolepid assemblages from Australia and Antarctica. Vertebrate and micro floral horizons in the Pertnjara Group are summarised, and an illustrated spine of Wuttagoonaspis sp. from basal Pertnjara Group sediments in the western Amadeus provides further evidence of correlation with the Mulga Downs Group of western New South Wales.

  • Dredge and core samples of sediments recovered from the west Tasmanian margin, South Tasman Rise and the Lord Howe Rise, on R.V. Sonne, are of possible Eocene, late Oligocene, early and late Miocene, early and late Pliocene, and Pleistocene or younger ages. Reworked Paleocene and Eocene specimens occur in some cores and dredge samples of late Oligocene age. Some cores show a major stratigraphical break from late Oligocene to Pleistocene. The coiling direction of Turborotalia pachyderma was investigated as a possible method of correlation of younger cores, and also as an indicator of palaeoclimatic changes. No correlation between cores was possible using coiling curves, which indicate rapid and irregular changes in sea-water temperatures over small areas, assuming that the coiling direction of T. pachyderma is an indication of sea-water temperature.

  • The United Nations Convention on the Law of the Sea gives Australia the option of proclaiming a Legal Continental Shelf around both the continent and its island territories, over which it would control exploration and exploitation of the natural resources of the seabed and subsoil. A Legal Continental Shelf is considered to extend throughout the natural prolongation of the land territory to the outer edge of the continental margin, which, where it extends beyond the 200 nautical mile limit (Exclusive Economic Zone - EEZ), is defined by a two-part formula based on measurements from foot of continental slope reference points. To fully use this formula, both bathymetric and sediment thickness information are required. The area of a Legal Continental Shelf around Australia and its territories would be approximately 12 million km2 (about 1.5 times the area of the continent itself), which would be one of the largest Legal Continental Shelves in the world. Eight regions of this shelf, totalling more than 3 million km2, would extend beyond an EEZ. Sediment thicknesses greater than 2000 m - sufficient to have generated hydrocarbons from any potential source rocks - occur in six of these regions: Lord Howe Rise / Norfolk Ridge, South Tasman Rise, Great Australian Bight, Naturaliste Plateau, Exmouth/ Wallaby Plateaus and Kerguelen Plateau. Most of the remote parts of the Australian margin with possible resource potential would lie within a Legal Continental Shelf. Our relative rating of petroleum potential of regions beyond an EEZ is based on both a qualitative and quantitative assessment. The potential petroleum recovery estimates are greatest for western Lord Howe Rise and the southern Kerguelen Plateau, but relatively high values were also obtained for the South Tasman Rise and the eastern flank of Lord Howe Rise. Of the deepwater ocean basin areas, the New Caledonia Basin has the greatest potential recovery, although the estimates are clearly unrealistically large. Small but potentially high-yielding basins, such as the Taranui Sea Valley on the Norfolk Ridge, are also of interest. Over all, the assessment indicates that the western flank of Lord Howe Rise has the greatest petroleum potential, even though the relatively small size of some of its individual basins tends to downgrade the chance of finding giant and thus economically viable fields. However, this part of Lord Howe Rise appears more promising when the equivalent area and potential within an EEZ around Lord Howe Island are considered. The southern Kerguelen Plateau produced the largest potential petroleum recovery estimates of any of the moderate water depth regions; however, its real potential will remain unknown until its origin (continental or oceanic) and volcanic history are better understood. Although the regions discussed are in relatively deep water (generally over 1000 m), they are not consistently any deeper than areas of plateaus and slopes within an EEZ, such as the Exmouth Plateau, which has been explored and drilled. Since areas with petroleum potential beyond an EEZ are remote, and in some cases in hostile environments, their exploration is unlikely to be economically viable in the near future; however, they may well provide Australia with a strategic resource into the next century. In the light of Australias dwindling petroleum resources, these regions should not be overlooked in long-term planning by government and industry.

  • The marine invertebrate macrofauna from the upper part of the Blenheim Subgroup of the Bowen Basin and the Kulnura Marine Tongue of the Sydney Basin is described. The fauna is assigned to 12 genera, one of which - Pseudonucula - is newly recognised, and to 13 species, of which one is new. On the basis of these descriptions and existing published information, three zones are recognised in the Blenheim subgroup, in ascending order, the Martiniopsis magna, the Martiniopsis pelicanensis and the Martiniopsis havilensis zones. An explanation is given of the conclusions of Waterhouse and Jell (1983) about the lower part of the subgroup. From the fauna, particularly the occurrence of Martiniopsis havilensis, it is concluded that a hiatus occurs in the Blenheim Subgroup between the Black Alley Shale and the Peawaddy Formation in the southwestern part of the Bowen Basin, and that the Black Alley Shale is equivalent to the MacMillan Formation in the central part of the basin and the Exmoor Formation in the northeastern part. The upper part of the Blenheim Subgroup (zone of Martiniopsis havilensis) seems to be younger than the Mulbring Shale of the Sydney Basin, and the Kulnura Tongue is not likely to be significantly younger than the Blenheim Subgroup. The faunas described appear to be younger than Kungurian, but are not likely to be younger than the Kazanian. They are rather low in diversity relative to older Permian faunas in the two basins, and this probably reflects the rather restricted marine conditions at the end of the open sea in the two basins.