No abstract available

Three Aptian and Albian (Lower Cretaceous) dinoflagellate cysts from coastal basins along the western margin of Australia are described. Two are new species, Cannosphaeropsis australis and Ovoidinium striatum, while Craspedodinium indistinctum Cookson & Eisenack 1958 is redescribed and emended. These dinoflagellate cyst taxa have stratigraphical utility in the Aptian and Albian of Australia and Papua New Guinea.

The Arunta Region of central Australia exposes the southern margin of the North Australian Craton and contains a record of multiple Proterozoic craton margin processes over a 1500 million year period. The place of mafic magmatism in this evolution is constrained by SHRIMP U-Pb dating of zircon, which is a primary igneous phase in the evolved sectors of mafic-ultramafic plutons across the region. The earliest mafic magmatism was in the 1800-1810 Ma Stafford Event, which is the first thermal system recognised in the region. Mafic plutons from this event may correlate with other expressions of mafic magmatism northwards within the craton. A second episode of mafic magmatism is recognised at 1770-1790 Ma (Yambah Event) and lacks correlatives elsewhere in the craton, as do all subsequent Arunta Region mafic magmatic events. Zircon overgrowths in Stafford- and Yambah-age plutons record conversion of these early intrusions into granulite grade metamorphic complexes during the Strangways Event, a regionally pervasive metamorphic system whose termination at ca. 1690 Ma coincided with local intrusion of dolerite dykes. Gabbro intrusion at ca. 1640 Ma in the Liebig Event is restricted within the Warumpi Province which is recognised as a separate terrane in the south of the region. There is no record of a mafic magmatic component to the ca. 1590 Ma Chewings event and most of the earlier intrusions do not record metamorphism at this time. Later mafic magmatic systems include pyroxenite intruded as part of the Mordor Complex at ca 1130 Ma (Teapot Event); and both erupted and intruded basaltic magma are components of the fault-bound Irindina Province which experienced high grade metamorphism during the Ordovician (Larapinta Event). The dating establishes that each of these craton margin event systems includes a mafic magmatic component, which suggests that repeated extensional systems are an important component of the tectonic evolution.

This article focuses on the re-evaluation of the source rock potential of the basal Kockatea Shale in the offshore portion of the northern Perth Basin.

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.

As Australia separated from Antarctica and drifted northward the Tasmanian Gateway opened, allowing the Antarctic Circumpolar Current to develop. This current began to isolate Antarctica from the influence of warm surface currents from the north, and an ice cap started to form. Eventually, deepwater conduits led to deepwater circulation between the southern Indian and Pacific Oceans. The existence of these conduits ultimately allowed ocean conveyor circulation. Continuing Antarctic thermal isolation, caused by the continental separation, contributed to the evolution of global climate from relatively warm early Cenozoic ?Greenhouse? to late Cenozoic ?Icehouse? climates. ODP Leg 189 addressed the interrelationships of plate tectonics in the gateway, circum-polar current circulation, climate and sedimentation, and global climatic changes. DSDP drilling had led to a basic framework of paleoenvironmental changes associated with gateway opening, but was not a full test of the various interrelationships. Using the DSDP results, Kennett, Houtz et al. (1975) proposed that climatic cooling and an Antarctic ice sheet (cryosphere) developed from ~33.5 Ma as the ACC progressively isolated Antarctica thermally. They suggested that development of the Antarctic cryosphere led to the formation of the cold deep ocean and intensified thermohaline circulation. Leg 189 gathered data that support this hypothesis. Leg 189 continuously cored sediments in the gateway, which was once part of a Tasmanian land bridge between Australia and Antarctica. The bridge separated the Australo-Antarctic Gulf in the west from the proto-Pacific Ocean to the east. This region is one of the few in the Southern Ocean where almost complete Cenozoic marine sequences could be drilled in paleo-water depths that were shallow enough to allow preservation of calcareous micro-organisms for isotopic studies. The Leg 189 sequences described by Exon, Kennett, Malone et al. (2001) reflect the evolution of a tightly integrated and dynamically evolving system over the past 70 million years, involving the lithosphere, hydrosphere, atmosphere, cryosphere and biosphere. The most conspicuous changes in the region occurred over the Eocene-Oligocene transition (Figure 1) when Australia and Antarctica finally separated. Before the separation, the combination of a warm climate, nearby continental highlands, and considerable rainfall and erosion, flooded the region with siliciclastic debris. Deposition kept up with subsidence. After separation, a cool climate, smaller more distant landmasses, and little rainfall and erosion, cut off the siliciclastic supply. Pelagic carbonate deposition could not keep up with subsidence. Leg 189 confirmed that Cenozoic Antarctic-Australia separation brought many changes. The regional changes included: warm to cool climate, shallow to deep water deposition, poorly ventilated basins to well-ventilated open ocean, dark deltaic mudstone to light pelagic carbonate deposition, microfossil assemblages dominated by dinoflagellates to ones dominated by calcareous pelagic microfossils, and sediments rich in organic carbon to ones poor in organic carbon.

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.

Measured probability distributions of shoreline elevation, swash height (shoreline excursion length) and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions. The theoretical distributions are based on assumptions that the time series are weakly steady-state, ergodic and a linear random process. Despite the swash process being inherently non-linear, our results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution. The RMS-errors for a range of exceedence level statistics (50, 10, 5, 2, and 1 percent) were restricted to <10 cm (and often <5 cm) for all of the swash variables that were investigated. The results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic-type morphodynamic modeling of beach response to waves. Further work is required, however, to relate the parameters of swash probability distributions to wave conditions further offshore.

No abstract available

Australia's offshore petroleum industry has come a long wa y since the drilling of the first offshore well in 1964 but by World standards, Australia is still relatively unexplored.