The National Geochemical Survey of Australia: The Geochemical Atlas of Australia was published in July 2011. Released along with this publication was a digital copy of the geochemical dataset that included basic particle size data. This dataset includes extended particle size data for NGSA samples.

In this study of the beach-ridge plain at Keppel Bay, on the central coast of Queensland, we examine ridge morphology, sediment texture and geochemistry. We build a detailed chronology for the ridge succession using the optically stimulated luminescence (OSL) dating method. Although our interpretations are preliminary, our results suggest that significant changes have occurred in the rate of shoreline accumulation of sediment, catchment sediment source areas, and that there have been minor falls in relative sea level.

Increased loads of land-based pollutants associated with land use change are a major threat to coastal-marine ecosystems globally. Identifying the affected areas and the scale of influence on marine ecosystems is critical to assess the ecological impacts of degraded water quality and to inform planning for catchment management and marine conservation. Studies using remotely-sensed data have contributed to our understanding of the occurrence and extent of influence of river plumes, as well as to assess exposure of ecosystems to river-borne pollutants. However, refinement of plume modelling techniques is required to improve risk assessments. We developed a novel approach to model exposure of coastal-marine ecosystems to river-borne pollutants. The model is based on supervised classification of true-colour satellite imagery to map the extent of plumes and to qualitatively assess the dispersal of pollutants in plumes. We use the Great Barrier Reef (GBR) to test our approach. We combined frequency of plume occurrence with spatially-distributed loads (based on a cost-distance function) to create maps of exposure to suspended sediment and dissolved inorganic nitrogen. We then compared annual exposure maps (2007-2011) to assess inter-annual variability in the exposure of coral reefs and seagrass beds. Our findings indicate that classification of true colour satellite images is useful to map plumes and to qualitatively assess exposure to river-borne pollutants. This approach should be considered complementary to remote sensing methods based on ocean colour products used to characterise surface water in plumes. The proposed exposure model is useful to study the spatial and temporal variation in exposure of coastal-marine ecosystems to riverine plumes. Observed inter-annual variation in exposure of habitats to pollutants stresses the need to incorporate the temporal component in exposure and risk models.

During 2009-10 Geoscience Australia completed a petroleum prospectivity study in the offshore northern Perth Basin, 200 km northwest of Perth. In some parts of this basin acoustic basement is deep and not resolved in the reflection seismic data. Improvements to the magnetic ship-track database and magnetic anomaly grid produced during the study allowed for assessment of depth to magnetic sources, and estimation of sediment thickness, and provided new insight into basement trends. 2.5D models along several transects, and analysis using spectral methods indicate penetration of the lower sediments by high-susceptibility bodies is necessary to approximate the observed magnetic anomaly. The reflection seismic evidence for these bodies is not obvious, though in some cases they may be associated with interpreted faults. Where the modelled bodies penetrate the sediments, they are mostly below or within the Permian section, except in the west of the study area where sediments thin over oceanic crust. On the northern-most profiles a large positive magnetic anomaly (the Batavia Ridge) is modelled by massive bodies whose tops are 5-10 km below sea floor. On these and other profiles to the south other dyke-like bodies rarely penetrate to shallower than 5 km below the sea floor.

Legacy product - no abstract available

Widespread seagrass dieback in central Torres Strait, Australia has been anecdotally linked to the delivery of vast quantities of terrigenous sediments from New Guinea. The composition and distribution, and sedimentological and geochemical properties, of seabed and suspended sediments in north and central Torres Strait have been determined to investigate this issue. In northern Torres Strait, next to Saibai Island, seabed sediments comprise poorly sorted, muddy, mixed calcareous-siliciclastic sand. Seabed sediments in this region are dominated by aluminosilicate (terrigenous) phases. In central Torres Strait, next to Turnagain Island, seabed and suspended sediments comprise moderately sorted coarse to medium carbonate sand. Seabed sediments in this region are dominated by carbonate and magnesium (marine) phases. Mean Cu/Al ratios for seabed sediments next to Saibai Island are 0.01, and are similar to those found in New Guinea south coastal sediments by previous workers. Mean Cu/Al ratios for seabed sediments next to Turnagain Island are 0.02, indicating an enrichment of Cu in central Torres Strait. This enrichment comes from an exogenous biogenic source, principally from foraminifers and molluscs. We could not uniquely trace terrigenous sediments from New Guinea to Turnagain Island in central Torres Strait. If sediments are a factor in the widespread seagrass dieback in central Torres Strait, then our data suggest these are marine-derived sediments sourced from resuspension and advection from the immediate shelf areas and not terrigenous sediments dispersed from New Guinea rivers. This finding is consistent with outputs from recently developed regional hydrodynamic and sediment transport models.

The Ceduna Sub-basin of the deep-water frontier Bight Basin contains a Middle Jurassic-Late Cretaceous sedimentary succession in excess of 15 km thick. Nine offshore exploration wells have been drilled in the basin, mostly clustered around the inboard edge of the Ceduna Sub-basin. As a result, the distal mid-Late Cretaceous strata predicted to contain potential source rock facies, had previously not been sampled. The presence of high quality source rocks in the basin was therefore an open question. 2D seismic data was used to delineate targets for sampling of the pre-Campanian section of the basin. Identified targets included potential source intervals of Albian-Santonian age at locations on the seaward edge of the Ceduna and Eyre Terrace where canyon formation, slumping and faulting have exposed the section. Also, a series of sites were selected to test for potential hydrocarbon seepage in the basin. These sites include areas where recently reactivated deep-seated faults were exposed at the seafloor, basin margin areas where facies thin, and areas where possible seepage was identified from Synthetic Aperture Radar (SAR) data. In February and March 2007, a 3-week marine acquisition programme was carried out on the RV Southern Surveyor. Potential dredge targets were first surveyed with 30 kHz EM300 swath bathymetry and observed with Topaz 3.5 kHz sub-bottom profiler. Near-live swath processing and slope analysis techniques enabled site specific dredge sampling of seafloor terrains where Cretaceous section outcropped or slopes were sufficient to ensure only a thin cover of overlying sediments. Targets include fault scarps and eroded sides of canyons. A better-than-expected number of successful dredges were collected (total of 37) from water depths ranging from 1600-4500m. Geochemical analysis of 259 dredge samples for total organic carbon (TOC) and pyrolysis yields (Rock Eval) identified good to very good organic richness in 13 samples, with TOC values between 2.1% and 6.2%. Of these, seven show liquids potential with Hydrocarbon Index (HI) values ranging between 274 and 479 (mgHC/TOC). The rocks with the best source rock characteristics came from high priority sampling sites in the westernmost Ceduna Sub-basin. Organic geochemical analysis has provided evidence for preservation of organic matter under anoxic conditions close to or at the sediment-water interface. Biostratigraphic analysis of these organic-rich rocks has yielded an age around the Cenomanian-Turonian boundary. Although the dredged rocks are immature for hydrocarbon generation, interpretation of an extensive seismic grid across the basin and petroleum system modelling have shown that this succession occurs with the oil window in the central Ceduna Sub-basin. The results of this study provide the best evidence to date for the presence of good quality liquids-prone source rocks in the basin, successfully addressing a key industry concern in this petroleum exploration frontier.

The hot rock geothermal model in the Australian context comprises high-heat producing granites overlain by thick accumulations of low-thermal conductivity sediments. The granites have low concentrations of radiogenic elements, and over hundreds of millions of years, these elements decay and produce heat. The passage of this heat to the Earth's surface via upwards conduction is slowed by layers of sediments that have low thermal conductivity, creating 'hot spots' beneath the blankets. This thematic map shows granites attributed by heat production and basin depth. The majority of the granites depicted are of surface outcrop. The presence of high-heat producing granites adjacent to deep sedimentary basins may be used as a first-order indicator of where to further investigate the possibility of hot rock geothermal plays. The main frame of the map shows all granites (attributed by calculated heat production - where available), sedimentary basins (and their order e.g. where one basin is overlapped by another) and geothermal licences and applications. The top right inset map shows only those granites with a calculated radiogenic heat generation of >5 uW -3, with the depth of the sedimentary basins. This map provides a rapid view of areas that may be expected to have the greatest hot rock potential. The second-from-top inset map shows all suitable geochemical analyses from OZCHEM, attributed by calculated radiogenic heat generation. This shows both the distribution of data that goes into attributing the granite polygons, and also analyses of granites (and other rocks) that fall outside the mapped granite polygons that are otherwise excluded from the main map. The third-from-top inset map shows the distribution of drillholes with temperature measurements. The bottom inset map shows an image of the Austherm07 database, which is derived from the drillhole temperature information. The image shows the projected temperature of the crust at a depth of 5 kilometres, interpolated between the drillholes. Overlain on this image is the small number of publicly-available heat flow data.

As at January 1997, one hundred and eighty seven petroleum accumulations had been discovered in the Bowen and Surat Basins. Commercial petroleum production has taken place from ninety nine of these accumulations. Both oil and gas has been recovered from Jurassic, Triassic, Permian and Devonian reservoirs in the Bowen/Surat sequence. Gas production takes place from accumulations lying on the western flank of the Taroom Trough via a gas gathering system and pipeline to Brisbane and from the Denison Trough, where gas is transported by pipeline to Gladstone. The most prolific petroleum producing units in the Taroom Trough are the Showgrounds Sandstone (Triassic), Precipice Sandstone (Jurassic) and Evergreen Formation (Jurassic). In the Denison Trough to the north, the most significant reservoir is the Aldebaran Sandstone, where over fifty percent of the remaining gas reserves in the Denison Trough are found. Gas production from many of the gas accumulations on the western flank of the Taroom Trough is currently in decline. Total remaining gas reserves for the western flank of the Taroom Trough have been estimated at 2298 million cubic metres (as at 30/06/96, QDME), while in the Denison Trough, 2931 million cubic metres of recoverable gas is thought to remain in the identified accumulations in the Bowen Basin sequence. Moonie, the largest oil accumulation found in the Bowen and Surat Basins to date, was discovered early in the exploration history of the two basins (1961) and provided the initial stimulus for an expanded exploration effort in the area. The oil at Moonie is trapped in a large, anticlinal closure on the upthrown side of a major, north-south trending thrust fault on the eastern margin of the Taroom Trough. 'Look-alike' plays to Moonie, (associated with the thrust faulting on the eastern basin margin), have been drilled with only limited success. A number of small oil accumulations have been identified, both to the north of Moonie on the same structural trend and on the western flank of the Taroom Trough. However, the Moonie accumulation appears to be unique and it is likely that future oil discoveries in the Bowen and Surat Basins will be small (less than 50 megalitres). The oil from Moonie is produced directly into the Jackson-Moonie oil pipeline while the oil from many of the small producing oil accumulations on the western flank of the basin is trucked to the Moonie facility. The Moonie accumulation is nearing depletion, with only 173 megalitres of recoverable oil remaining from initial reserves of 3859 megalitres (as at 30/06/96, QDME). In spite of this, over sixty percent of the remaining, identified oil reserves in the Bowen and Surat Basins are reservoired at Moonie.

This report was Commissioned by Geoscience Australia for the Western Tasmania Regional Minerals Program (WTRMP). It was completed by SRK Consulting, and is listed as Report AG701. The report covers the interpretation of economic basement in the Bass Basin, and documents the production of a SEEBASE model.