The Early Cretaceous non-marine volcaniclastic Eumeralla Formation accumulated in a rift basin on the southern margin of Australia during the break-up of eastern Gondwana. Wireline-Iog analysis and a range of sedimentary data have helped to discriminate three major basin-wide informal lithostratigraphic units in the formation. From the base of the formation they are: Eumeralla I: siltstone/mudstone/sandstone/coal; Eumeralla II: siltstone/mudstone/thin lithic sandstone; and Eumeralia III: volcaniclastic sandstone. A fourth unit - Eumeralla IV: siltstone/sandstone/coal - occurs throughout the western Otway Basin, but is absent, probably because of erosion, from the central and eastern pans of the basin. The bases of all four lithostratigraphic units are probably diachronous. The succession of lithostratigraphic units Eumeralla I- IV is interpreted as representing coal swamps and flood plains of low-energy streams; shallow and deep freshwater lakes; channel tracts and flood plains of high-energy streams; and channel tracts, flood plains and coal swamps of low- energy streams respectively. Sedimentary facies analysis of outcropping Eumeralla II and Eumeralla III in the eastern Otway Basin confirms the interpretations for these units. The basin-wide extent of the three lower lithostratigraphic units implies that a single integrated drainage system for the entire basin was established at the onset of Eumeralla Formation deposition, and persisted at least until the late Albian. This inference is supported by the close correlation between variations in lithology and depositional environments and the Aptian- Albian sea-level changes. However, intrabasinal volcanism significantly influenced sedimentation and was probably the primary control on basin drainage.

Relationships, thicknesses, and palaeocurrent and other sedimentary data applying to facies associations in Eumeralla Formation outcrops in the eastern Otway Basin distinguish at least three discrete depositional systems (A-C). Each system is characterised by high-energy fluvial flows in broad channel tracts. The multistorey sandstone bodies of system A, between Cape Otway and Apollo Bay, are up to 70 m thick and contain varying proportions of basement-derived quartzose gravel and sand intermixed with mainly volcaniclastic sand. Interchannel siltstones also up to 70 m thick separate the sandstone bodies. Palaeocurrents in system A have an overall southerly trend. This system is interpreted to represent deposition in a medial alluvial fan to proximal braided-stream system. System B occurs around Moonlight Head, and may extend southeast to Rotten Point. It is characterised by multistorey sandstone bodies up to 14 m thick separated by siltstones of similar thickness which locally contain thin coal beds, rooted horizons, and reddened soil profiles. It lacks basement-derived gravel. Palaeocurrents trend north-easterly to northwesterly. The sediments of system B accumulated on a medial to distal braid plain. Facies associations and fluvial architecture of system C, seen in outcrop north of Skenes Creek, resemble those of system B, from which it is distinguished by consistently northwest palaeocurrent vectors, a basement-derived gravel component, and the absence of debris flows and volcanic pebbles. System C also represents deposition on a braid plain or in a braided-river system. The three depositional systems are accommodated in a model for the Eumeralla Formation which suggests that its volcanic detritus was derived largely from infrarift volcanic complexes in the axial parts of the Otway rift basin, which during the Aptian-Albian lay to the south of the present coastline. A volcaniclastic apron spread northwest to northeast across the basin (system B). Elevated basement blocks shed quartzose detritus into flanking alluvial fans, the more distal parts of which mixed with volcaniclastic detritus (systems A, C). The onset of axial volcanism in the Aptian may have displaced a former westerly axial drainage towards the northern basin margin (system C).

Undiscovered hydrocarbon resources of the Bowen and Surat Basins in southern Queensland have been evaluated, on the basis of data compiled by the NGMA project Sedimentary Basins of Eastern Australia, including regional-scale seismic horizon and isopach maps and an extensive geochemical database of petroleum and potential source-rock samples. Estimates of the yields of hydrocarbons, calculated using the geochemical material balance method, are of very significant magnitude for both oil and gas. Although six principal source-rock intervals are recognised, over two-thirds of the oil is sourced from the Late Permian Baralaba interval. For gas, the Permian Buffel-Banana source unit contributes 31.5%, a significantly greater proportion than its oil counterpart, although, again, the Baralaba source unit is the most prodigious interval, yielding 40% of the total gas. A break-down of the yield in terms of major periods reveals that the Cretaceous to present-day window is by far the most important for both oil and gas generation, with 94.6% and 91.4 % of the respective totals. Thus, late structuring is more important for trap integrity than earlier structuring. By demonstrating that large quantities of hydrocarbons are potentially available for entrapment, the yield analysis should act as a stimulus to exploration initiatives, particularly in the search for stratigraphic traps.

Aluminium and iron concentrations and partitioning between particulate, colloidal and dissolved forms were examined in acid run-off from known acid sulphate soil environments in the lower Richmond River catchment during dry season conditions. Chronically acid drains in the Tuckean Swamp and Rocky Mouth Creek exhibited extremely high concentrations of dissolved metals (8- 10 mg/L Al , 5mg/L Fe). Dissolved aluminium and iron were quickly transformed to solid hydroxide species, which were rapidly removed from the water column by the aggregation and precipitation of diaspore and hematite in distinct flocculation zones, as water was subjected to steep pH and salinity gradients. This suggests that high metal concentrations may be found in benthic sediments and biota. Dissolved metals in acid runoff represent a major source of environmental pollution and, combined with the effects of acidity and low dissolved oxygen levels, pose a significant threat to estuarine ecosystems.

Iron Cove, Hen and Chicken Bay, Homebush Bay, and Rozelle/Blackwattle Bay are offchannel embayments on the southern shoreline of Port Jackson. These shallow (<8 m water depth) embayments are mantled by bioturbated surficial sediments of easily resuspended oxic material (>90% mud), termed the hydrous layer. Sediment in these offchannel embayments is highly enriched in metallic and organic contaminants and each embayment is characterised by a distinct ratio of heavy-metal concentrations. Heavy-metal concentrations and total-organic and sulphur contents of sediments decrease rapidly seaward from storm water canals and other point sources. Sediment traps deployed at six locations in Iron Cove, each week for two periods of 16 and 26 weeks, provide time-integrated samples and settling rates of particulate matter from the overlying water column. Settling rates recorded during summer deployments were four times higher than during winter. Comparable heavy-metal concentrations between settling particulate matter and the ambient hydrous layer at each trap location imply that the majority of the trapped material is derived by resuspension. The relative contribution of the many processes which may resuspend surficial estuarine sediment, e.g. physical (wind-generated waves, tidal action , stormwater runoff), biogeochemical (bioturbation, flocculation and dispersion), and anthropogenic (trawling, boating, engineering construction) are discussed. The implications of these findings are that toxicants bound in sulphidic sediments are continuously remobilised into the water column. Resuspension and secondary sourcing of highly contaminated sediments probably occurs in many of the extensive shallow water environments of Port Jackson and other affected estuarine systems, thereby providing a pathway for contaminants to enter the foodchain.

The Delepinea aspinosa brachiopod Zone comprises two subzones: the Inflatia elegans and Linoprotonia tenuirugosa Subzones. Multivariate (cluster) analysis is used to identify benthic marine fossil communities (recurrent species associations) in samples collected from all known fossiliferous intervals of these subzones in the study area. The Euclidean distance coefficient, a weighted-pair grouping method, and a standardised data set are used to form dendrographic clusters inferred to represent recurrent species associations (communities). The results parallel those from faunas of the succeeding Rhipidomella fortimuscula Zone, i.e. several communities are evident and some species are numerically significant in more than one community. The communities of each subzone appear to intergrade rather than form rigid, depth-limited assemblages. Faunas of the I. elegans Subzone cluster into four communities, including the Unispirifer striatoconvolutus community, present in substrates near or below wave-base on a marine shelf. The I. elegans community is closest in species composition to the U. striatoconvolutus community, but does not occupy the same geographic range; it may be a precursor community. Two other communities, the Rhipidomella australis and Leptagonia analoga communities, overlap in range with the first two communities and are inferred to have occurred in a mid-shelf setting. Faunas of the subsequent faunal assemblage, the Linoprotonia tenuirugosa Subzone, are present on marine shelf substrates influenced by an actively prograding shoreline. The Rhipidomella australis community persisted into this subzone with a modified species composition. The Rugosochonetes careyi community is a new element.

The Monaro Volcanic Province in southeastern New South Wales is an Early to Middle Tertiary intraplate volcanic province of lava field style, similar to the Newer Volcanic Province of southwestern Victoria. The lava pile is dominated by nepheline basanite, alkali olivine basalt and transitional basalt with minor olivine tholeiite and nepheline hawaiite. Olivine nephelinite lavas occur near the top of the lava pile. The lavas are interbedded with Tertiary sediments and hyaloclastites, some of which have formed in lakes, probably developed by lava damming the pre-basaltic drainage. Thick weathering profiles, in some cases bauxitic, are developed on many of the flows in the lava pile, suggesting long breaks between eruptions at particular sites. This is consistent with sporadic eruplions from widely scattered vents. Most known eruption sites in the province are represented by volcanic plugs of aphanitic to coarse-grained nepheline basanite, olivine nephelinite, nepheline hawaiite and alkali olivine basalt. Fractionated varieties of these rocks also occur together with minor feldspar-rich and titanian augite-rich cumulates. The predominant plug type is aphanitic to fine-grained nepheline basanite, containing mantle xenoliths and/or kaersutite amphibole. Basement fractures have had a major influence on the position of volcanic centres. Plugs are concentrated along two northwest trending linear zones: the Bemboka Zone in the north; and the Berridale-Towamba Zone in the south. The Berridale Fault-Towamba Lineament is a major crustal feature of the region. Other basement structures, including north-northeast-trending faults , appear to have controlled some eruption centres away from the two major zones.

Thirty-seven spicule-dominated clasts from limestone breccia in the lower part of the Upper Ordovician Malongulli Formation of the Cliefden Caves area, central New South Wales, have yielded a collection of 2657 conodonts. These have been assigned to 48 species, dominated by Belodina confluens Sweet, Besselodus sp., Dapsilodus mutatus (Branson and Mehl)?, Drepanoistodus suberectus (Branson and Mehl), Oistodus cf. venustus Stauffer, Panderodus gracilis (Branson and Mehl), Paroistodus? sp. A Nowlan and McCracken, Scabbardella altipes subsp. B Orchard and Walliserodus amplissimus (Serpagli). Two new species are described, Pseudobelodina? anceps and Taoqupognathus tumidus. This allochthonous assemblage is a mixture of North American Midcontinent and North Atlantic-type pelagic elements, reflecting derivation from warm shallow and cooler deeper zones of the low-latitude, offshore Malongulli site . These spicule-dominated clasts probably formed initially as periplatform-ooze deposits at the outer margins of an island platform, then were incorporated in debris flows and transported basinward to become associated with the basal, in situ, graptolitic siltstone-shale Malongulli succession. The graptolite horizons are late Eastonian in age (Zone of Dicranograptus hians kirki). There is little evidence of reworking of the conodonts from older horizons. Twelve species have close North American Midcontinent affinities and may be correlated, using graphic methods, with the lower half of the Zone of Oulodus velicuspis, i.e. within the North American mid-upper Edenian Stage. This establishes upper limits for the age of the underlying pre-Malongulli carbonate succession, and confirms the Malongulli Formation as distinctive and much younger than the Darriwilian-early Gisbornian Malongulli-type succession to the east of Cliefden Caves.

The Cobar district, in western New South Wales, is host to several small to medium, sediment-hosted polymetallic precious- and base-metal orebodies (Au-Cu-Ag-Pb-Zn). Gold and base metals have been mined there since 1870, and production (to end 1995) has been calculated at 2.5 million ounces Au, ~0.6 Mt Cu, 1500 t Ag, 0.6 Mt Pb, and 1.2 Mt Zn (Stegman and Stegman 1996). The metal content of the known deposits has been estimated at 1 Mt Cu, 1.6 Mt Pb, 2.6 Mt Zn, 4000 t Ag, and 70 t Au (Schmidt 1990). One new deposit (McKinnons) has been discovered in the 1990s, while deep drilling at existing deposits continues to add to ore reserves. Production in 1997 was from the Elura (Pb-Zn- Ag), CSA (Cu-Ag-Pb-Zn), Peak (Au-Cu), and McKinnons (Au) mines. This review summarises the main features that define Cobar-style deposits and reviews the key factors critical to the genesis of the known deposits. Exploration methods that might be used to find analogous deposits both within the basin and in other terranes are also reviewed.

The Tasman Fold Belt System in New South Wales includes three out-cropping fold belts: the Neoproterozoic-Early Palaeozoic Kanmantoo Fold Belt, the Early Palaeozoic-Carboniferous Lachlan Fold Belt, and the Early Palaeozoic-Triassic New England Fold Belt. Substantial production of metal has come from mineral deposits in the Lachlan and New England Fold Belts and from alluvial deposits in their cover rocks. The Kanmantoo Fold Belt has a restricted range of mineralisation, which includes stratiform(?) iron-rich copper lodes in metamorphosed mafic volcanics, lead-silver veins and gold-quartz veins. Geological similarities with Victoria and Tasmania suggest potential for gold and base metals developed in Late Proterozoic-Cambrian mafic arc rocks. The Lachlan Fold Belt contains a wide range of deposits. The most important types are porphyry, epithermal and skarn-type copper, copper-gold, and gold deposits developed in Ordovician basaltic and andesitic volcanics (shoshonites) and associated intrusives; base-metal and gold deposits, with both volcanogenic (VMS) and thrust-related features, in Silurian felsic volcanic-sedimentary rock trough and basin sequences; tin, gold and smaller tungsten, molybdenum and base-metal deposits in Silurian and Early Devonian granites; large gold and base-metal deposits in Early Devonian turbiditic rocks in the Cobar region (Cobar-type deposits), probably formed during deformation and closure of the Cobar Basin; and gold vein deposits in folded sedimentary rocks, for example at Hill End. There is good potential for discovery of further deposits within the Lachlan Fold Belt and in extensions under cover rocks. The main targets are deposits related to Ordovician and Silurian volcanism, Cobar-type deposits and deposits associated with sutures and thrusts. Recent investigations suggest that a poorly understood, but possibly widespread, Late Carboniferous-Early Permian metallogenic epoch occurs in eastern Australia, covering parts of the Lachlan and New England Fold Belts. The New England Fold Belt in New South Wales can be characterised as a tin, gold, antimony province. Deposits formed in a variety of settings. The most important associations are: base-metal deposits in Early Permian felsic volcanics; gold-silver-base-metal deposits in Late Permian felsic to intermediate volcanics of the Drake area; tin, gold, molybdenum, bismuth and tungsten deposits associated with Late Permian-Early Triassic granites; and metahydrothermal gold, antimony and tungsten-bearing quartz veins occurring in faults, shears and joints commonly associated with regional dislocations (and thought to have formed from metamorphic dehydration of accreted sediments and volcanics). Recent exploration has located epithermal gold mineralisation in Early Permian intermediate and felsic volcanic centres, in previously unexplored areas of the Tamworth Zone in the west of the New England Fold Belt, which were probably related to rifting in the foreland (Meandarra Rift).