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  • In September and October of 2011 Geoscience Australia surveyed part of the offshore northern Perth Basin in order to map potential sites of natural hydrocarbon seepage. The primary objectives of the survey were to map the spatial distribution of seepage sites and characterise the nature of the seepage at these sites (gas vs oil, macroseepage vs microseepage; palaeo vs modern day seepage) on the basis of: acoustic signatures in the water column, shallow subsurface and on the seabed; geochemical signatures in rock and sediment samples and the water column; and biological signatures on the seabed. Areas of potential natural hydrocarbon seepage that were surveyed included proven (drilled) oil and gas accumulations, a breached structure, undrilled hydrocarbon prospects, and areas with potential signatures of fluid seepage identified in seismic, satellite remote sensing and multibeam bathymetry data. Within each of these areas the survey acquired: water column measurements with the CTD; acoustic data with single- and multi-beam echosounders, sidescan sonar and sub-bottom profiler (sidescan not acquired in Area F as it was too deep in places); and sediment and biological samples with the Smith-McIntyre Grab. In addition, data were collected with a remotely operated vehicle (ROV), integrated hydrocarbon sensor array, and CO2 sensor in selected areas. Sampling with the gravity corer had limited success in many of the more shallow areas (A-E) due to the coarse sandy nature of the seabed sediments. This dataset comprises sediment oxygen demand measurements from the upper 2 cm of seafloor sediments.

  • This is the Acreage Release Marine Environmental Data compiled web service to be updated each year with acreage release. It contains the following publicly available datasets, for the 2016 Acreage Release - Marine Survey Towed-video Transects, Marine Sediments Database Samples, Australian Seascapes, Seabed Mud Content on the Northwest Shelf, Seabed Sand Content of the Northwest Shelf and Seabed Gravel Content of the Northwest Shelf.

  • We report the presence of a prominent bathymetric expression of the Fitzroy River palaeochannel on the continental shelf of the southern Great Barrier Reef (GBR), Australia. The Fitzroy River, and the Burdekin River are the two largest point sources of terrigenous sediment to the GBR, which represents the worlds largest tropical mixed siliciclastic-carbonate sedimentary province. The Fitzroy River palaeochannel differs from that of the previously discovered Burdekin palaeochannel in that it has not yet been buried by sediments. Evidently, the dominance of platform reef rather than barrier reef geomorphology, coupled with macrotidal oceanographic conditions has limited aggradation behind the shelf edge, as postulated for the Burdekin region. Contrary to current models for the central GBR which suggest that slope sedimentation is limited to periods of transgression, the palaeo-Fitzroy probably contributed sediment directly to the continental slope of the southern GBR throughout the lowstand. Additionally, it appears that during the highstand, accumulation of terrigenous sediment on the middle and outer shelf has been minimal. The southern GBR represents a transition between the mainly terrigenous wave and ocean current dominated shelf of southeastern Australia, and the mixed siliciclastic-carbonate storm-influenced shelf of the GBR. The discovery of the Fitzroy River palaeochannel in the southern GBR physiographic setting provides new data by which the response of major rivers to sea level change can be characterised.

  • The production of icebergs from Antarctic ice shelves represents fluctuations in the mass of the icesheet. Mapping the age, distribution and size of iceberg scour marks on the seafloor provides insight into the dynamics of the icesheet and circulation patterns through time. Sidescan sonar records from the Prydz Bay continental shelf are used to determine the relative ages of scour marks on this shelf as modern, relict and very relict, and their width, length and orientation. Modern scour marks on this shelf are shown to occur at average depths of 285 m, up to a maximum of 400 m. This range is broadly consistent with modern keel depths (248-352 m) for icebergs produced from the Amery Ice Shelf. Relict scours occur at average depths of 486 ± 78 m, while very relict scours occur at average depths of 650 ± 60 m. No iceberg scours are observed at depths greater than 750 m. The depth range of relict scours is consistent with iceberg scouring during periods of lower glacial sea level, combined with the production of icebergs with larger keel depths during major deglaciations. The very deep setting of the oldest scours implies the production of icebergs from a very thick iceshelf, possibly relating to major retreat of the icesheet towards the grounding line during periods of extreme glacial retreat.

  • In September and October of 2011 Geoscience Australia surveyed part of the offshore northern Perth Basin in order to map potential sites of natural hydrocarbon seepage. The primary objectives of the survey were to map the spatial distribution of seepage sites and characterise the nature of the seepage at these sites (gas vs oil, macroseepage vs microseepage; palaeo vs modern day seepage) on the basis of: acoustic signatures in the water column, shallow subsurface and on the seabed; geochemical signatures in rock and sediment samples and the water column; and biological signatures on the seabed. Areas of potential natural hydrocarbon seepage that were surveyed included proven (drilled) oil and gas accumulations, a breached structure, undrilled hydrocarbon prospects, and areas with potential signatures of fluid seepage identified in seismic, satellite remote sensing and multibeam bathymetry data. Within each of these areas the survey acquired: water column measurements with the CTD; acoustic data with single- and multi-beam echosounders, sidescan sonar and sub-bottom profiler (sidescan not acquired in Area F as it was too deep in places); and sediment and biological samples with the Smith-McIntyre Grab. In addition, data were collected with a remotely operated vehicle (ROV), integrated hydrocarbon sensor array, and CO2 sensor in selected areas. Sampling with the gravity corer had limited success in many of the more shallow areas (A-E) due to the coarse sandy nature of the seabed sediments. This dataset comprises mineraology of the upper 2cm of seabed sediment. The mineral assemblage includes quartz, aragonite, calcite and high-Mg calcite expressed as mol %.

  • This data represents the percentage of time the Shields parameter (Shields, 1936) exceeds 0.25. The Shields parameter (non-dimensional bed shear stress) value of 0.25 is assumed to be the threshold for creating disturbed patches on the seabed. This value is several times larger than that required to initiate traction bedload transport (~0.05) and falls in the middle of the ripple and dune bedform stability field. It represents conditions when the seabed is highly mobile and where patches of disturbed habitat are likely to be created. Shields, A. 1936. Application of similarity principles and turbulence research to bed-load movement. Mitteilunger der Preussischen Versuchsanstalt f¨ur Wasserbau und Schiffbau 26: 5-24

  • The Marine Survey Geomorphology Web Map Service contains the local scale (1:10 000) interpreted geomorphology maps available for download on Geoscience Australia's website. These interpreted geomorphology maps have been produced for numerous marine survey programs conducted in Australian mainland and Antarctic waters by both Geoscience Australia and our collaborators. Layers are grouped by survey or region and where available include both the Geoscience Australia and vessel survey identification numbers that contributed to each dataset.

  • Publicly available bathymetry and geophysical data has been used to map geomorphic features of the Antarctic continental margin and adjoining ocean basins at scales of 1:1-2 million. The key bathymetry datasets used were GEBCO08 and ETOPO2 satellite bathymetry (Smith & Sandwell 1997), in addition to seismic lines in key areas. Twenty-seven geomorphic units were identified based on interpretation of the seafloor bathymetry with polygons digitised by hand in ArcGIS.

  • The legacy of multiple marine transgressions is preserved in a complex morphology of ridges, mounds and reefs on the Carnarvon continental shelf, Western Australia. High-resolution multibeam sonar mapping, underwater photography and sampling across a 280 km2 area seaward of the Ningaloo Coast World Heritage Area shows that these raised features provide hardground habitat for modern coral and sponge communities. Prominent among these features is a 20 m high and 15 km long shore-parallel ridge at 60 m water depth. This ridge preserves the largely unaltered form of a fringing reef and is interpreted as the predecessor to modern Ningaloo Reef. Landward of the drowned reef, the inner shelf is covered by hundreds of mounds (bommies) up to 5 m high and linear ridges up to 1.5 km long and 16 m high. The ridges are uniformly oriented to the north-northeast and several converge at their landward limit. On the basis of their shape and alignment, these ridges are interpreted as relict long-walled parabolic dunes. Their preservation is attributed to cementation of calcareous sands to form aeolianite, prior to the post-glacial marine transgression. Some dune ridges abut areas of reef that rise to sea level and are highly irregular in outline but maintain a broad shore-parallel trend. These are tentatively interpreted as Last Interglacial in age. The mid-shelf and outer shelf are mostly sediment covered with relatively low densities of epibenthic biota and have patches of low-profile ridges that may also be relict reef shorelines. An evolutionary model for the Carnarvon shelf is proposed that relates the formation of drowned fringing reefs and aeolian dunes to Late Quaternary eustatic sea level.

  • Understanding and predicting the bio-physical relationships between seabed habitats, biological assemblages, and marine biodiversity is critical to managing marine systems. Species distributions and assemblage structure of infauna were examined on the oceanic shelf surrounding Lord Howe Island (LHI) relative to seabed complexity within and adjacent to a newly discovered relict coral reef. High resolution multibeam sonar was used to map the shelf, and identified an extensive relict reef in the middle of the shelf, which separated an inner drowned lagoon from the outer shelf. Shelf sediments and infauna were sampled using a Smith McIntyre grab. The three geomorphic zones (drowned lagoon, relict reef and outer shelf) were strong predictors or surrogates of the physical structure and sediment composition of the LHI shelf and its infaunal assemblage. Infaunal assemblages were highly diverse with many new and endemic species recorded. Each zone supported characteristic assemblages and feeding guilds, with higher abundance and diversity offshore.