Sediments of the Late Palaeozoic Urana Formation in infrabasins beneath the Cainozoic Murray Basin include glaciomarine diamictite, fine-grained sediment, sandstone, and conglomerate facies. The facies assemblage is dominated by paratillites, formed by ice-rafting, and fine-grained sediments with a small ice-rafted component. Rhythmically bedded siltstone and claystone, sediment gravity-flow diamictites, traction-current deposits, and, possibly, subglacial tillites are also present. Interpretation of the facies indicates that grounded-ice deposits are absent from the glaciomarine sequence over large areas of the basin and has enabled estimation of the likely limits of grounded ice. Palaeontological and sedimentological evidence suggests that these rocks were deposited towards the end of the major Late Palaeozoic glaciation of southeastern Australia.

A new zygomaturine diprotodontid, Hulith erium tomasellii gen. et sp. nov., from 38 000-year-old swamp sediments at Pureni, Southern Highlands Province, Papua New Guinea is the largest mammal yet known from the Quaternary of New Guinea. Possibly the sister taxon to species of Zygomaturus, the new genus is represented by a partial skull and parts of the postcranial skeleton. Estimated to have weighed 75-200 kg, H. tomasettii was probably a browser. Its hindlimb morphology suggests that it had a greater joint mobility than is known in any other diprotodontid, and this in turn hints that it was probably not graviportal.

The western part of the Arunta Inlier, central Australia, consists of major northward-tilted blocks separated by major thrust faults - the Anmatjira, Napperby, Redbank-Mount Zeil and Mount Sonder-Mount Razorback faults-associated with major Bouguer gravity anomalies. The Redbank-Mount Zeil thrust zone (RTZ) separates a granulite-facies suite to the north from a paragneiss-migmatite-orthogneiss suite to the south. This fault is marked by major radiometric, magnetic, and morphological discontinuities, and consists of northward-dipping protomylonite, mylonite, ultramylonite, and phyllonite, formed under a heterogeneous ductile shear- regime. Kernels of granulite, paragneiss, and migmatite abound. The RTZ truncates all other structures and postdates all juxtaposed units. Dynamothermal activity along the RTZ about 1000-900 Ma ago may be reflected by possibly reset Rb-Sr ages in blastoporphyritic gneisses and migmatite to the north and south, respectively. Major Palaeozoic movements are indicated by Devonian fanglomerate (Brewer Conglomerate), while younger reactivation is suggested by morphological features. Two alternative models are considered: (1) an antecedent of the RTZ formed an early boundary between an older igneous-dominated granulite block to the north and a younger amphibolite-facies paragneiss belt to the south prior to about 1600 Ma ago; or (2) contemporaneous granulite and paragneiss terrains representing different depth zones within a vertically zoned crust were allochthonously juxtaposed by the thrusting. The uplift of basic granulites along the RTZ is estimated from thermobarometric measurements to be at least 20 km, accounting for the Papunya Bouguer anomaly high of more than 500 µm/s2 . The emplacement of deep-seated basic intrusions, the ensuing geothermal rises, and crustal anatexis may have been genetically and temporally related.

Seismic data recorded in deep water have several features that make them very well suited to migration by the use of a simple, constant velocity algorithm. A case is made for such migrations to be applied routinely to deep·water data .

Volcanic and intrusive rocks of Permian age, ranging from basalt and andesite through granodiorite and dacite to rhyolite, are sparsely but non-randomly distributed in the western Georgetown Inlier, including newly recognised areas in the Croydon region. The basaltic to andesitic rocks are typical intra-plate transitional alkaline rocks, apparently genetically unrelated to the granodiorite/dacite to rhyolite group, which are a suite of fractionated I-type (and possibly A-type) rocks, lower in alkalis, derived from evolved (old) crustal source rocks. The Permian magmatism appears to have been controlled by northwest-trending, and some north-trending, major fractures. Carboniferous igneous rocks in the same region, although only slightly different in chemistry, include a much greater proportion of felsic ignimbrites relative to more mafic extrusive rocks, and are related to north-south aligned and/or elongated sag-type cauldron structures. Total volumes, relative proportions of mafic and felsic rocks, and, to some extent, their compositions, appear to be related to tectonic style.

In the area 30-33°S, 116-118°E of the Southwest Seismic Zone of Western Australia, ML -4.0 earthquakes for the period 1960-1983 do not fit a Poisson model. However, when foreshocks and aftershocks are excluded, the hypothesis of a Poisson distribution cannot be rejected for the resulting series of main shocks. A similar result holds for the subset of ML -5.0 events for the period 1949- 1983. Consequently, when earthquake risk is being assessed by methods that assume a Poisson distribution, foreshocks and aftershocks should be excluded . However, the consequent apparent reduction of risk caused by removing these potentially damaging earthquakes should be pointed out. Although records of seismicity are probably incomplete for the early part of this century, there appears to have been an increase in numbers of ML -4.0 events, starting around 1949. Although, the data are too uncertain to test the increase in the ML -4.0 main shocks statistically, there has been an approximate five-fold increase in the mean yearly number of ML -4.5 main shocks during the period 1949 to 1983, compared with the period 1923 to 1948. This is clearly larger than would be expected from a Poisson process. Consequently, the apparent increase in the number of ML -4.0 events is probably also real and not an artefact of a Poisson process. Also, there were no ML -5.0 events during the period 1923 to 1948, and the only two ML -6.0 earthquakes this century took place in 1968 and 1979. This increase in seismicity since the late 1940s should be taken into account in the interpretation of earthquake risk calculations.

Host rocks to the Coronation Hill U-Au mine have long been regarded as agglomerate occupying a volcanic vent, and, as such, the deposit has been regarded as volcanogenic and radically different from the other U-Au stratabound, unconformity-related deposits of the South Alligator Valley district. The agglomerate is reinterpreted as a polymictic debris-flow conglomerate, consisting of rounded to angular clasts of quartz, quartzite, sandstone, carbonaceous shale, rhyolite, and volcaniclastics in a greywacke matrix. Its development was unrelated to volcanism. The deposit lies on the flank of a basinal conglomerate-sandstone-volcanic succession (Coronation Sandstone of the late Early Proterozoic El Sherana Group) that is unconformable on carbonaceous shale (Early Proterozoic Koolpin Formation). The ore surrounds an intensely faulted wedge-shaped area of conglomerate, altered volcanics, and carbonaceous schist. Uranium mineralisation is classified as epigenetic sandstone type, with uranium-enriched felsic volcanics as the source rock, sandstone beds as conduit rocks, and the carbonaceous schist, either as fault wedges or as clasts in the conglomerate, acting as reductant. In other deposits of the region, precipitation took place within in-situ carbonaceous shale faulted against the conduit sandstone. Intense chlorite alteration in the volcanics is unrelated to uranium mineralisation, but may be related to the gold mineralisation, which in places forms ore shoots that are separate from uranium ore and pass into the altered volcanics.

The Lithgow earthquake of magnitude ML 4.3, which took place on 13 February 1985, was the largest earthquake to have occurred in the Blue Mountains region of New South Wales since the Kurrajong earthquake of 1919. It caused minor damage in Lithgow and Wallerawang and was felt as far away as Parkes and Dubbo, 200 km from the epicentre. The total damage was estimated at approximately $65 000. Macroseismic and instrumental evidence suggests that, for this earthquake, the attenuation to the northeast in and under the Sydney Basin was much greater than the attenuation to the southwest through the Lachlan Fold Belt.

New earthquake risk maps of southwest Western Australia including continental margins have been prepared. The risk is depicted as contours of peak ground velocity, acceleration, and ground intensity with a 10 per cent probability of being exceeded in 50 years. The maps are based on the Cornell-McGuire methodology. Ten earthquake source zones have been thus defined and corresponding recurrence relations derived. The relation obtained, using a maximum-likelihood fit, for the primary zone to the east of Perth, is log N = 3.66-0.90 ML, where N is the number of events greater than or equal to the Richter magnitude, ML. Local intensity attenuation constants, a, b, and c, are derived for the expression I = aebMLR-c, where I is the estimated Modified Mercalli intensity at a hypocentral distance R km from an earthquake of magnitude ML. Using the relation log A= I/3.1-2.3 to convert the intensity to peak ground acceleration, A in m.s-2, the adopted constants were 0.025, 1.10 and 1.03 respectively. Similarly, using the empirical formula 21 = 7v/5 to convert intensity to peak ground velocity, v in mm.s-1, the corresponding values were 3.30, 1.04 and 0.96, respectively. The contour expressing the greatest risk in the area of interest is that of a peak ground velocity of 160 mm.s-1, and it encloses an area of about 2000 km2 centred on the most active source zone east of Perth. The value for Perth city is 48 mm.s-1. Increasing (i) the maximum magnitude from ML 7.5 to ML 8.5; (ii) the depth of earthquake foci from 5 km to 15 km; (iii) the b value from 0.90 to 0.94; and (iv) the attenuation constants to their estimated maximum value, in the primary source zone, changes the Perth velocity contour from 48 mm.s-1 to 56 mm.s-1 , 48 mm.s-1 , 42 mm.s-1 , and 58 mm.s-1, respectively. The omission of a suspected seismic gap 100 km east of Perth from the primary source zone changes the velocity contour from 48 mm.s-1 to 46 mm.s-1. Sensitivity to adopting another empirical relation between peak ground acceleration and intensity has been examined. This increases the risk at Perth from 0.44 m.s-2 to 0.65 m.s-2. We recommend a microzonation study of Perth and installation of more strong-motion instruments to improve our risk estimates, which should be updated in 5-10 years.

A solution is presented for the practical determination of the direction of magnetism in core samples from drill holes.