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  • The seafloor morphology mapping approach used to derive this dataset follows Geoscience Australia’s draft National Seafloor GeoMorphology (NSGM) mapping scheme (Nanson and Nichol, 2018). The NSGM scheme is an extension of the Dove et al. (2016) approach, which characterises the seafloor in two sequential parts: Part 1 maps the seafloor Morphology (shape) using bathymetry data, and Part 2 uses additional data to interpret seafloor Geomorphology for those mapped morphological shapes. Part 1 of the NSGM scheme was applied to the project dataset, and consists of three hierarchical levels: Province, Surface and Feature. This dataset contains Surface shapefiles that comprise three categories: Plane (<2 degrees), Slope (2-10 degrees) and Escarpment (>10 degrees).This dataset is published with the permission of the CEO, Geoscience Australia

  • Darwin Harbour is the primary sea port for northern Australia, for which accurate information on the seabed is critical and required by multiple stakeholders. These stakeholders include the offshore energy industry, the fishing industry, and government authorities responsible for managing the harbour, in particular, the Port Authority. Darwin harbour is macrotidal with large areas of shallow (<10 m) subtidal and intertidal flats, dissected by bifurcating channels with localised areas of hardground. These hardground areas provide substrate for epibenthic communities. To support the informed management of Darwin Harbour, Geoscience Australia (GA), in collaboration with the Northern Territory Department of Land Resource Management (DLRM), the Australian Institute of Marine Science (AIMS) and the Darwin Port Corporation, conducted a multibeam survey of the harbour in 2011 on board MV Matthew Flinders. This was followed in 2013 by a physical sampling (sediments and video) survey by GA in collaboration with DLRM on board MV John Hickman. This paper presents results from those surveys with a focus on techniques used to produce a spatially continuous map of the harbour floor showing the distribution of hard and soft substrate types. The Darwin Harbour surveys acquired multibeam sonar data (bathymetry and backscatter) across 180 km2 gridded to 1 m resolution, 61 seabed samples and 35 underwater video observations to map and classify the seabed into habitats. Primary geomorphic features identified in Darwin Harbour include channels, banks, ridges, plains and scarps. Within the study area, acoustically hard substrates are associated with hard ground and relatively coarse seabed sediments. The hard grounds (rock, reef and coral gardens) are found mostly on banks and often overlain by a veneer of sandy sediment. In contrast, acoustically soft substrates are associated with fine sediments (mud and fine sand) that form the plains and channels. A seascape analysis was used to classify the seabed, incorporating information from multibeam data, underwater video characterisations and seabed hardness predictions. We used the Iterative Self Organising (ISO) Unsupervised Classification technique to combine the information from five variables (bathymetry, slope, rugosity, backscatter and probability of hard seabed (p-rock)) to form a single seabed habitat classification. The p-rock variable was derived by comparing the angular backscatter response of known areas of hard seabed to all other angular backscatter responses. We found that six habitat classes were statistically optimal based on the distance ratio measure. These six classes are related to a unique combination of seabed substrate, relief, bedform, presence of a sediment veneer and presence of epibenthic biota and rock/reef (hard substrate). The results presented here demonstrate the value of acoustic data for the characterisation of the seabed substrate that provides key habitats for benthic biota. This study also highlights the utility of the p-rock variable for habitat mapping at the level of distinguishing areas of hard seabed from soft sediment areas. The resultant seabed habitat maps are being used by the Northern Territory DLRM to inform ongoing management of Darwin Harbour, with additional mapping planned for offshore areas and adjacent harbours in the region.

  • Three areas in the Torres Strait-Gulf of Papua region were selected for detailed study of sediments and benthic fossil biota. These areas form a transect across the shelf from the Fly River Delta to the shelf edge, near the northern extremity of the Great Barrier Reef. The Torres Strait-Gulf of Papua shelf is a shallow, low-gradient platform, where the shelf edge occurs between 120 and 140 m depth. In the study area, where the sediments range from muddy to gravelly carbonate sands, the sediment deposition rates are low and the relict content of sediment is often high. The three areas show distinct differences in benthic foraminiferal assemblages as indicated by relative abundances at the order level, as well as distribution patterns of individual species; these differences are also reflected in the total microbiotic communities. Given the high relict content in the surface material across these sites, a foraminiferal preservation scale was developed to assess the extent of reworking. Taphonomic features indicate that abrasion is the main factor affecting preservation. Despite poor preservation of the foraminiferal tests, the benthic foraminiferal species have a strong correlation to water depth, indicating that transportation pathways are short. Application of multivariate statistics to analyze the relationship between environmental attributes and the distributions of the microbiota and foraminiferal species indicates the additional importance of factors including percent carbonate mud, percent gravel, organic carbon flux, temperature, salinity and mean grain size. The benthic foraminifera produce a much stronger correlation to the environmental variables than the microbiota, indicating that these organisms can provide a detailed assessment of habitat types.

  • Geoscience Australia undertook a marine survey of the Leveque Shelf (survey number SOL5754/GA0340), a sub-basin of the Browse Basin, in May 2013. This survey provides seabed and shallow geological information to support an assessment of the CO2 storage potential of the Browse sedimentary basin. The basin, located on the Northwest Shelf, Western Australia, was previously identified by the Carbon Storage Taskforce (2009) as potentially suitable for CO2 storage. The survey was undertaken under the Australian Government's National CO2 Infrastructure Plan (NCIP) to help identify sites suitable for the long term storage of CO2 within reasonable distances of major sources of CO2 emissions. The principal aim of the Leveque Shelf marine survey was to look for evidence of any past or current gas or fluid seepage at the seabed, and to determine whether these features are related to structures (e.g. faults) in the Leveque Shelf area that may extend to the seabed. The survey also mapped seabed habitats and biota to provide information on communities and biophysical features that may be associated with seepage. This research, combined with deeper geological studies undertaken concurrently, addresses key questions on the potential for containment of CO2 in the basin's proposed CO2 storage unit, i.e. the basal sedimentary section (Late Jurassic and Early Cretaceous), and the regional integrity of the Jamieson Formation (the seal unit overlying the main reservoir). This dataset comprises total chlorin concentrations and chlorin indices from the upper 2cm of seabed sediments.

  • <p>This resource contains surface sediment data for Outer Darwin Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Northern Territory Government (Department of Land Resource Management) during the period from 28 May and 23 June 2015 on the RV Solander (survey SOL6187/GA0351). This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Land Resource Management, and co-investment from Geoscience Australia and Australian Institute of Marine Science. The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions. The specific objectives of the survey were to: <p>1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay; <p>2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and <p>3. Collect tidal data for the survey area. <p>Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles. This dataset comprises O2 consumption and CO2 production rates measured from core incubation experiments conducted on seabed sediments. <p>A detailed account of the survey is provided in: <p>Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas, W.A., Potter, A., Radke, L.C., Tran, M., Williams, D. and Whiteway, T., 2015. Outer Darwin Harbour Marine Survey 2015: GA0351/SOL6187 Post-survey report. Record 2016/008. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2016.008

  • This dataset provides the spatially continuous data of predicted seabed gravel content (sediment fraction greater than 2000 µm) expressed as a weight percentage ranging from 0 to 100%, presented in 0.0025 decimal degree (dd) resolution raster grids format and ascii text file. The dataset covers the north-northwest region of the Australian continental EEZ. This dataset supersedes previous predictions of seabed gravel content for the region with demonstrated improvements in accuracy. Accuracy of predictions varies based on density of underlying data and level of seabed complexity. Artefacts occur in this dataset as a result of insufficient samples in relevant areas. This dataset is intended for use at regional scale. The dataset may not be appropriate for use at local scales in areas where sample density is insufficient to detect local variation in sediment properties. To obtain the most accurate interpretation of sediment distribution in these areas, it is recommended that additional samples be collected and interpolations updated.

  • Keppel Bay is a large shallow coastal embayment adjacent to the mouth of the Fitzroy River, located on the central coast of Queensland. The geomorphology and distribution of sediment in Keppel Bay is complex due to the influence of Late Quaternary sea-level change, relict topography, a geologically diverse catchment, macrotidal hydrodynamic processes and flood events. Seabed morphology, sub-bottom profiles and sediment cores reveal the former path of the Fitzroy River across Keppel Bay and the continental shelf. The palaeo-Fitzroy River flowed west across the shelf to the north of Northwest Reef, a position on the shelf that is now under approximately 60 m of water. With the rise in sea level during the early Holocene, the mouth of the Fitzroy River retreated across the continental shelf and by the middle Holocene it was landwards of its present location, near Rockhampton. During the last few thousand years under a relatively stable sea level, much of the shallow inner region of Keppel Bay has been infilled and the coast has prograded several kilometres. Palaeochannels in the inner section of Keppel Bay have mostly been infilled with sediment, which mainly comprises muddy sand from the Fitzroy River. In the outer bay and on the shelf further west many relict channels have not been infilled with marine sediment indicating that the area is relatively starved of sediment. Sediments in outer Keppel Bay are dominantly relict fluvial deposits that are well sorted with only a minor mud component. Subaqueous dunes in the outer southeastern section of Keppel Bay and Centre Bank indicate that tidal currents and currents associated with the predominant southeasterly winds, appear to be transporting marine biogenic sediments and relict coarse terrigenous sediments into Keppel Bay.

  • In this study, we aim to identify the most appropriate methods for spatial interpolation of seabed sand content for the AEEZ using samples extracted on August 2010 from Geoscience Australia's Marine Samples Database. The predictive accuracy changes with methods, input secondary variables, model averaging, search window size and the study region but the choice of mtry. No single method performs best for all the tested scenarios. Of the 18 compared methods, RFIDS and RFOK are the most accurate methods in all three regions. Overall, of the 36 combinations of input secondary variables, methods and regions, RFIDS, 6RFIDS and RFOK were among the most accurate methods in all three regions. Model averaging further improved the prediction accuracy. The most accurate methods reduced the prediction error by up to 7%. RFOKRFIDS, with a search window size of 5, an mtry of 4 and more realistic predictions in comparison with the control, is recommended for predicting sand content across the AEEZ if a single method is required. This study provides suggestions and guidelines for improving the spatial interpolations of marine environmental data.

  • 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 major and trace element concentrations in marine sediments.

  • Several grounding zone wedges were left on the floor and flanks of Prydz Channel in western Prydz Bay by the Lambert Glacier during the last glacial cycle. Seismic profiles indicate that vertical accretion at the glacier bed was the most important depositional process in forming the wedges, rather than progradation by sediment gravity flows. Sidescan sonographs reveal extensive development of flutes on the sea floor inshore from the wedges, indicating deformable bed conditions beneath the ice. The region inshore of the east Prydz Channel wedge features extensive dune fields formed by currents flowing towards the grounding zone. This orientation is consistent with models of circulation beneath ice shelves in which melting at the grounding line generates plumes of fresher water that rise along the base of the ice shelf, entraining sea water into a circulation cell. The Lambert Deep is surrounded by a large composite ridge of glacial sediments. Internal reflectors suggest formation mostly by subglacial accretion. The sea floor in the Lambert Deep lacks dune fields and shows evidence of interspersed subglacial cavities and grounded ice beneath the glacier. The absence of bedforms reflects sea floor topography that would have inhibited the formation of energetic melt water-driven circulation.