New 2D seismic data acquired in the Mentelle Basin by Geoscience Australia in 2008-09 has been used for a seismic facies study of the post-rift succession. The Mentelle Basin is a large deep to ultra deep-water, frontier basin located on Australia's southwestern margin about 200 km southwest of Perth. The study focused on the post-rift sequences deposited following the breakup between Australia and Greater India. Stratigraphic wells DSDP 258 and DSDP 264 provide age and lithological constraints on the upper portion of the post-rift succession down to mid-Albian strata. The depositional environment and lithology of the older sequences are based on analysis of the seismic facies, stratal geometries and comparisons to the age equivalent units in the south Perth Basin. Fourteen seismic facies were identified based on reflection continuity, amplitude and frequency, internal reflection configuration and external geometries. They range from high continuity, high amplitude, parallel sheet facies to low continuity, low amplitude, parallel, subparallel and chaotic sheet, wedge and basin fill facies. Channel and channel fill features are common in several facies along with a mounded facies (probably contourite) and its associated ponded turbidite fill. A progradational sigmoidal to oblique wedge facies occurs at several stratigraphic levels in the section. A chaotic mound facies, probably comprising debrite deposits, has a localised distribution.

Dense hydrocoral-sponge communities have been identified on the upper continental slope of George V Land, East Antarctica and declared Vulnerable Marine Ecosystems. Analysis of physical and biological datasets collected during the 2007/08 CEAMARC survey identified that the richest communities are found in the heads of canyons which receive Antarctic Bottom Water formed on the George V shelf, and the canyons harbouring rich benthos are also those that cut the shelf break. This led to several hypotheses regarding their distribution and three main factors were identified. These hypotheses were tested during a recent marine science voyage in January 2011 to the same region. Initial analysis of the new data supports the hypotheses regarding the physical controls on hydrocoral-sponge community distribution.

This study was undertaken as part of a program to collect baseline data from the seabed environments over the Van Diemen Rise, which comprises a series of carbonate platforms and banks in the eastern Joseph Bonaparte Gulf, northwest of Darwin. Samples were collected during a survey on board the RV Solander in August and September 2009. The state of saturation for the different carbonate minerals (aragonite, calcite, high-magnesium calcite) was calculated for each sampling site from the ratio of the ion activity product and the solubility product. The carbonate ion concentration used for the ion activity product was calculated from total alkalinity and pH. The solubility products of the carbonate minerals were derived from literature data, e.g. the solubility for high-magnesium calcite as a function of the mol% MgCO3 was based on experimental results by Plummer and Mackenzie (1974, American Journal of Science vol. 274, p. 61-83). The calculated average state of saturation was 1.4 (range: 0.8-1.9) for high-magnesium calcite, 4.2 (range: 3.4-4.6) for aragonite, and 6.4 (range: 5.1-6.8) for calcite. Values close to 1 suggest the mineral is in thermodynamic equilibrium with ambient water, which is the case for high-magnesium calcite. In contrast, aragonite and calcite are distinctively supersaturated. Given the near-equilibrium state of high-magnesium calcite, this mineral phase will likely be lost over a time scale of decades as ocean acidification progresses. This ongoing process will alter the sediment composition significantly given the high abundance of high-magnesium calcite. This study supports the concept of using high-magnesium calcite as an indicator for the progression of ocean acidification where surface sediments have been sampled and preserved over time.

This record contains the preliminary results of Geoscience Australia marine survey 238 (SS04/2003) to southeast Gulf of Carpentaria. The survey was completed between 9 May and 10 June 2003 using Australia's national facility research vessel Southern Surveyor. The survey included Geoscience Australia and CSIRO and Marine and Atmospheric Research scientists.

We combine two- and three-dimensional seismic stratigraphic interpretation with paleobathymetric analysis from benthic foraminifera to understand the genetic significance of prominent seismic discontinuity surfaces typically mapped as "sequence boundaries" and "flooding surfaces" in the late Paleogene-early Neogene Northern Carnarvon Basin. The progradational succession, dominated by heterozoan carbonate sediments, is divided into five northwest-prograding clinoformal sequences and 19 sub-sequences. Clinoform fronts progress from smooth to highly dissected, with intense gullying apparent only after the mid Miocene optimum. Once initiated, gullies become the focus for sediment distribution across the front. Bottomsets remain relatively sediment-starved without the development of aprons on the lower slope and basin. Small-scale variability suggests heterogeneous sediment dispersal through the slope conduits. Along-strike sediment transport superimposed on progradation changes from south-directed in the late Oligocene to north-directed in the late mid-Miocene suggesting a major reorganization of circulation in the southeastern Indian Ocean. Prominent seismic discontinuity surfaces represent both intervals of shallow paleo-water depth and flooding of the shelf. Partial exposure of the shelf indicated by karst morphology is coeval with middle to outer neritic paleo-water depths on the outer shelf. Rather than build to sea-level, progradation occurs with shelf paleo-water depths at the clinoform rollover >100 m. Therefore, in the Northern Carnarvon Basin onlap onto the clinoform front is not coastal and the sensitivity of the clinoforms to sea-level changes is muted.

The Coompana Project is a collaborative project between Geoscience Australia and the Geological Survey of South Australia, co-funded by Geoscience Australia’s Exploring for the Future Programme and the South Australian Government’s PACE Copper Initiative. The Coompana Project aims to provide new precompetitive geological, geophysical and geochemical data in the under-explored Coompana Province in South Australia. The pre-drilling geophysics program was undertaken to assist the drilling process by reducing the uncertainty associated with intersecting the targeted stratigraphy. Seismic data were acquired at eight proposed drilling sites for the Coompana Drilling Program in February 2017. Seismic data were collected using vertical and horizontal geophones. An accelerated weight-drop source was tested with metal and plastic strike plates. The plastic strike plate was preferred and used for all sites. P-wave reflection images were used to images subsurface layers and estimate bedrock depth at each drill site. Horizontal geophone data indicated S-wave data had higher resolution than the vertical geophone P-wave data, but initial testing did not provide good bedrock imaging. Fan shots can indicate zones of low velocity weathering at the near surface. Multichannel Analysis of Surface Waves provided near surface weathering profiles. Near surface weathering can be an indication of caves in this limestone environment. The S-wave shot records may indicate the presence of caves with S-wave signal degradation at cave locations, as S-waves do not travel through voids, not noticed at these sites. The seismic reflection method can be used to show subsurface variations and provide bedrock depth estimates, though the bedrock can be difficult to identify. The data is very noisy and data quality changes at different locations. Seismic data quality can be improved with a higher energy source.

Cool-water carbonate environments may be responsible for up to one third of the carbonate sediment produced on continental shelves, and are useful modern analogues for many geologically ancient deposits. The extensive southern margin of the Australian continent is recognised as the world's largest modern example of a high energy, cool-water carbonate depositional realm. A number of studies have suggested that Quaternary sediment production here is largely influenced by oceanography, and that wave abrasion strongly limits sediment accumulation. Therefore, in this region the outer-shelf, below the storm wave base, is thought to be the focus of sediment accumulation. The inner shelf is considered a zone of active sediment production due to the proliferation of carbonate secreting organisms, although few studies have investigated sediment production or accumulation in this energetic and dynamic environment. The Recherche Archipelago, which sits at the western margin of the Great Australian Bight (GAB), was examined to better understand Quaternary shelf evolution and the importance of this type of inner shelf as a carbonate 'factory'. Surficial sediments, video, multibeam sonar data, cores and shallow seismics were collected. The present seabed of the archipelago features extensive areas where flat-lying limestones sit over the often irregular granite basement. The Pleistocene erosional surface is overlain by a coarse bivalve and rhodolith dominated gravel lag. Significantly, there are extensive Holocene deposits, up to 7 m thick, throughout the archipelago, particularly in association with granite islands. These deposits comprise cross-bedded gravelly carbonate sands dominated by fragments of calcareous algae (rhodoliths), molluscs and bryozoans. In contrast, the inshore and coast is dominated by terrigenous sediment. Seismic profiles and preserved palaeo-shoreline features suggest that slow but episodic aggradation of marine sediment has occurred on the inner shelf over successive Quaternary sea level cycles, although there are also extensive areas of non-deposition. This accumulation is partly attributable to the sheltering effect of high-relief granitic outcrops and cementation of subaerially exposed carbonate sediments.

Lord Howe Island in the southwest Pacific Ocean is surrounded by a shallow (20 - 120 m) sub-tropical carbonate shelf 24 km wide and 36 km long. On the mid shelf a relict coral reef (165 km2) extends around the island in water depths of 30 - 40 m. The relict reef comprises sand sheet, macroalgae and hardground habitats. Inshore of the relict reef a sandy basin (mean depth 45 m) has thick sand deposits. Offshore of the relict reef is a relatively flat outer shelf (mean depth 60 m) with bedrock exposures and sandy habitat. Infauna species abundance and richness were similar for sediment samples collected on the outer shelf and relict reef, while samples from the basin had significantly lower infauna abundance and richness. The irregular shelf morphology appears to determine the distribution and character of sandy substrates and local oceanographic conditions, which in turn influence the distribution of different types of infauna communities.

<div>The bulk rock stable isotopes database table contains publicly available results from Geoscience Australia's organic geochemistry (ORGCHEM) schema and supporting oracle databases for the stable isotopic composition of sedimentary rocks with an emphasis on calcareous rocks and minerals sampled from boreholes and field sites. The stable isotopes of carbon, oxygen, strontium, hydrogen, nitrogen, and sulfur are measured by various laboratories in service and exploration companies, Australian government institutions, and universities, using a range of instruments. Data includes the borehole or field site location, sample depth, stratigraphy, analytical methods, other relevant metadata, and the stable isotopes ratios. The carbon (¹³C/¹²C) and oxygen (¹⁸O/¹⁶O) isotope ratios of calcareous rocks are expressed in delta notation (i.e., &delta;¹³C and &delta;¹⁸O) in parts per mil (‰) relative to the Vienna Peedee Belemnite (VPDB) standard, with the &delta;¹⁸O values also reported relative to the Vienna Standard Mean Ocean Water (VSMOW) standard. Likewise, the stable isotope ratio of hydrogen (²H/¹H) is presented in delta notation (&delta;²H) in parts per mil (‰) relative to the VSMOW standard, the stable isotope ratio of nitrogen (¹⁵N/¹⁴N) is presented in delta notation (&delta;¹⁵N) in parts per mil (‰) relative to the atmospheric air (AIR) standard, and the stable isotope ratio of sulfur (³⁴S/³²S) is presented in delta notation (&delta;³⁴S) relative to the Vienna Canyon Diablo Troilite (VCDT) standard. For carbonates, the strontium (⁸⁷Sr/⁸⁶Sr) isotope ratios are also provided.</div><div><br></div><div>These data are used to determine the isotopic compositions of sedimentary rock with emphasis on the carbonate within rocks, either as minerals, the mineral matrix or cements. The results for the carbonate rocks are used to determine paleotemperature, paleoenvironment and paleoclimate, and establish regional- and global-scale stratigraphic correlations. These data are collated from Geoscience Australia records, destructive analysis reports (DARs), well completion reports (WCRs), and literature. The stable isotope data for sedimentary rocks are delivered in the Stable Isotopes of Carbonates web services on the Geoscience Australia Data Discovery Portal at https://portal.ga.gov.au which will be periodically updated.</div>

High-CO2 gas fields serve as important analogues for understanding various processes related to CO2 injection and storage. The chemical signatures, both within the fluids and the solid phases, are especially useful for elucidating preferred gas migration pathways and also for assessing the relative importance of mineral dissolution and/or solution trapping efficiency. In this paper, we present a high resolution study focussed on the Gorgon gas field and associated Rankin trend gases on Australia's Northwest Shelf of Australia. The Gorgon field is characterized by a series of stacked reservoirs (Figure 1), and is therefore well placed to characterize CO2 migration, dissolution and reaction by looking at geochemical signatures in the different reservoirs. Hydrological data at the Gorgon field also suggests that many of the major faults possess very low transmissivities, which should prevent or limit mixing of reservoir fluids with different chemical imprints. The gas data we present here reveal correlatable trends for mole %-CO2 and --C CO2 both areally and vertically as observed by Edwards et al. (2007). We suggest that the observed relationships are imparted due to mineral carbonation reactions that occurred along the CO2 migration pathway. These results have important implications for carbon storage operations and suggest that under certain conditions mineral sequestration might occur over longer migration distances and on shorter timescales than previously thought.