Magnetic, gamma-ray and gravity data sets provide vital information for mineral and petroleum explorers as well as researchers studying the geology of the Australian continent. Commonwealth and State and Territory governments have devoted considerable resources to acquiring these data sets and making them available to encourage exploration. Geoscience Australia's geophysical databases contain data acquired by governments, and this report summarises coverages over Australia of these data. On the occasion of the centenary issue of Preview, it is worth reflecting on the advances in the coverage of publicly available magnetic, gamma-ray and gravity data over Australia since the first edition of Preview in February 1986. Since then the areas and resolution of coverages have increased dramatically. Quality of the data through better acquisition and processing techniques has also improved, and new types of data sets added to the explorers' supplies.

Obtaining reliable predictions of the subsurface will provide a critical advantage for explorers seeking mineral deposits at depth and beneath cover. A common approach in achieving this goal is to use deterministic property-based inversion of potential field data to predict a 3D subsurface distribution of physical properties that explain measured gravity or magnetic data. Including all prior geological knowledge as constraints on the inversion ensures that the recovered predictions are consistent with both the geophysical data and the geological knowledge. Physical property models recovered from such geologically-constrained inversion of gravity and magnetic data provide a more reliable prediction of the subsurface than can be obtained without constraints. The non-uniqueness of inversions of potential field data mandates careful and consistent parameterization of the problem to ensure realistic solutions.

Geophysical data were acquired by Australia and Japan from 1994-2002 on the deep-water continental margin offshore from Queen Mary Land, East Antarctica in the general locality of Bruce Rise. This paper presents a regional interpretation of these data and outlines the tectonic history.

part page item. This article discusses the International Stratigraphic Guidelines and Australian practices relating to stratigraphic unit names, when there is a change to the name of the geographic feature that the unit is named after. Australian examples demonstrate both the advice of the Stratigraphic Guidelines not to change the unit name, and a particular case where it was more appropriate to change the unit name for local reasons.

Weather conditions during the survey were generally very good with only a few days of seas of about two metres. Technically and scientifically, the balance of the program changed when the seismic (and magnetic) program was reduced to one third of the expected kilometres because of the failure of the compressor. Fortunately, two of four critical lines running WNW-ESE were acquired (Table 1). Data acquisition rates (average of 200 km/day) were tolerable and seismic data quality was good. A whale watch was kept in accord with the requirements of the Department of the Environment and Heritage, but no whales were seen. The dredging program was increased to take advantage of the reduced seismic program, and most Mellish Rise sites were located either on the two new seismic lines or on pre-existing BMR continental margin survey seismic lines. A number of sites on the Kenn Plateau made use of seismic data from last year's Southern Surveyor Cruise SS5/04. The need to use BMR seismic lines moved the dredging balance to the western half of the area. Of the 44 dredges attempted, 37 (85 %) produced valuable results (Table 3). The swath-mapper was invaluable in designing dredge plans. The coring program of 5 cores (Table 2) produced three moderately successful cores, but was disappointing overall. The two seismic lines extend right across the Mellish Rise and reveal how the area has been affected by tension but not compression, with high blocks 50-100 km across separated by heavily sedimented graben of similar width. Satellite bathymetry and gravity maps, and the total seismic data set show that structural trends bounding the blocks are NW-SE, N-S and NE-SW. Numerous smaller horsts rise above the broad highs. Dredges from the Coriolis Ridge and the Selfridge Rise, both on the northern Kenn Plateau, are dominated by silicic volcanics of continental origin, siliciclastic sediments, and shallow marine carbonates (some reefal). Basaltic volcanics are rare. The continental volcanics may be rift-related (Upper Cretaceous to early Eocene). The calcarenites may be Eocene and Oligocene in age. Dredges from the generally deeper water (thinner crust) Mellish Rise are different, being dominated by basaltic volcanics and hyaloclastites, although silicic volcanics, siliciclastic sediments, and shallow marine carbonates (some reefal) occur. Two phases of volcanism, rift related (Upper Cretaceous to early Eocene) and hotspot related (late Eocene-Oligocene) may well be present. Three dredges from a southern protrusion of the Louisiade Plateau, which is not necessarily genetically related to that plateau, contain basaltic volcanics and hyaloclastites, silicic volcanics, siliciclastic rocks, and shallow marine carbonates in an assemblage like that of the Mellish Rise. Until exhaustive laboratory studies of the rocks are carried out, the above generalisations remain speculative. In the end, the volcanics could be related to any of four known periods of volcanism: ? The Late Jurassic (145-135 Ma) subduction-related volcanism of the Graham?s Creek Formation in the Maryborough Basin: tuffs, agglomerates and volcanic breccias, overlain by trachyte and rhyolite flows, overlain by basaltic andesite and dacite. ? The Early Cretaceous (125-115 Ma) explosive rift-related volcanism of the Whitsunday and Cumberland Islands: dacite, rhyolite, and andesitic ignimbrite. ? The assumed Late Cretaceous to Paleocene rift-related volcanism of the Marion Plateau (drilled in ODP Leg 194): altered basalt flows and volcaniclastic breccias and conglomerate. ? The Late Eocene to Early Oligocene hotspot volcanism of the Tasmantid chain: basalts and hyaloclastites.

Part-page item of matters related to stratigraphy. This column discusses informal units, the role of authors and reviewers, and is the 50th Stratigraphic Column produced by the Australian Stratigraphy Commission. Journal ISSN 0312 4711

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A Late Jurassic (Tithonian) suite of marine microplankton is present in the Flamingo Formation and its equivalents in the Timor Sea, offshore north-western Australia and adjacent regions. It includes three dinoflagellate cyst genera, Aidelacysta, Ampulladinium and Belowia, and ten species of dinoflagellate cysts which are described as new. The genera Balcattia, Biorbifera and Dissimulidinium are emended to note key morphological features observed in the material studied. The new dinoflagellate cyst species are Aidelacysta clavata, Ampulladinium variabile, Balcattia cheleusa, Batioladinium paeminosum, Belowia baltea, Biorbifera aggressiva, Cassiculosphaeridia solida, Dissimulidinium purattiense, Gardodinium angustum and Pseudoceratium robustum. An additional morphotype of Belowia, B. sp. A. is informally described and Meiourogonyaulax bulloidea is emended to note the microreticulate nature of the autophragm. Stanfordella granulosa is reported from the Southern Hemisphere for the first time. A new acritarch species, Nummus tithonica, is also described. These microplankton taxa have stratigraphical utility in the Tithonian Cribroperidinium perforans Zone to the upper Pseudoceratium iehiense Zone.