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  • Tropical cyclones affect storm-dominated sediment transport processes that characterise Holocene shelf deposits in many shelf environments. In this paper, we describe the geomorphology of reef talus deposits found in the Gulf of Carpentaria and Arafura Sea, Australia,that we attribute to tropical cyclones. The orientation of these deposits is also indicative of a consistent, along-coast transport pathway.

  • This web service displays the results of a marine survey conducted by Geoscience Australia in Commonwealth waters of the north-eastern Browse Basin (Caswell Sub-basin) between 9 October and 9 November 2014. The additional codes GA-0345 and GA-0346 refer to Geoscience Australia (GA) internal codes and TAN1411 is the vessel survey number given by the RV Tangaroa for 2014.

  • As part of the Australian Government's "New Oil" initiative, Geoscience Australia undertook a geophysical survey (the Southwest Frontiers Survey) of the south-western Australian continental margin in late 2004. The survey acquired 2700 km of industry-standard, 106-fold seismic data recorded to 12 seconds two-way time using a 6-8 km digital streamer and 4900 cui gun array. Marine reflection seismic acquisition was supplemented by recording of refraction seismic data by sonobuoys at sea and by land stations in the onshore/offshore observation scheme. Marine reflection survey shots were used as sources of seismic energy for both add-ons. The main scientific objectives of refraction work were: 1. Provide accurate seismic velocity information to improve depth conversion of reflection seismic data and to define type of basement and crust below it underneath the sedimentary basins. 2. Provide estimates of crustal thickness underneath major sediment deposition centres in the area to better constrain interpretation of tectonic evolution of the region. The new refraction seismic data have substantially supplemented coverage of the area resulting from old sonobuoy work and from very few onshore stations. When applied to a basement travel time pick interpreted in the multi-channel reflection data set, the new velocity data indicate a maximum sediment thickness in excess of 9 km. A comparison of stacking velocities and modelled sonobuoy data suggests that, unlike in other areas, stacking velocities from the Bremer Sub-basin survey 280 can be used as a reliable substitute for acoustic velocities down to 3 s two-way time into the sediments, for the purpose of calculating sediment thickness. One of the key findings of the refraction seismic study is that velocities in the basement are generally in the 5.2-5.6 km/s range, indicating that, contrary to priory expectations, basement in the area is mostly not granitic in composition. Results from the Bremer area conjugate counterpart in Antarctica obtained by the 50th Russian Antarctic Expedition (December 2004 - April 2005) also show low velocities in the basement on the inner side of Antarctic continent-ocean boundary, and therefore are consistent with our results from the Australian margin. If we combine all results available to us, it appears that a ~400km wide zone in Gondwana prior to break-up had basement velocities significantly lower than normal continental values of 6.0 - 6.2 km/s typical for granites and gneisses. The presence of low grade metasediments of the Albany-Fraser Province and its Antarctic equivalent is our preferred interpretation of this observation. Metasediments produce substantially less heat than granites and this leads to a different scenario, than granitic basement, for hydrocarbon maturation in the Bremer sub-basin, which is one of the targets of Geoscience Australia's Big New Oil program. Advanced burial and thermal geo-history modelling in this area was carried out for the first time in Australia without relying on default values (such as Heatflow or geothermal gradient) in modelling packages. Results of this work will be presented at the APPEA 2006 Conference. The similarities in seismic properties of the crust between the Bremer/Recherche area on the SW Australian continental margin and its conjugate on the Antarctic margin, has generated interest in Russia. As a result, planning of Russian Antarctic Expedition 51 (to start in December 2005) will take into consideration the need to record additional data at specific locations to answer questions of interest to both Australia and Russia.

  • On behalf of Australia, the Australian Transport Safety Bureau (ATSB) is leading search operations for missing Malaysian airlines flight MH370 in the Southern Indian Ocean. Geoscience Australia provided advice, expertise and support to the ATSB to facilitate bathymetric surveys, which were undertaken to provide a detailed map of the sea floor topography to aid navigation during the underwater search. Bathymetric data was acquired by multibeam sonar mounted on the hull of multiple vessels (GA survey reference: GA-4421, GA-4422 & GA-4430). Bathymetric surveys were conducted from June 2014 to February 2017, collecting over 710,000 square kilometres of data in the search area and along transit lines (to and from the search area). This dataset allows exploration of the seafloor topography through an optimal resolution compilation of tiles across the search and transit areas of the Southern Indian Ocean. The dataset is overlain on a hillshade created from the Optimal resolution bathymetry data. The hillshade was created with the parameters of point illumination azimuth at 45 degrees and altitude of 45 degrees.

  • The Murray Canyons are a group of deeply-incised submarine canyons on a steep 400-km section of the continental slope off Kangaroo Island, South Australia. Some of the canyons are amongst the largest on Earth. The canyons, some 80 km long, descend from the shelf edge to abyssal plain 5200 m deep. Sprigg Canyon, the deepest and one of the largest, has walls 2 km high. The thalwegs of the larger canyons are concave in profile, steepest on the upper continental slope (15?-30?), with about 4?gradient on the mid slope, then level out on the lower slope to merge with the 1? continental rise. Between canyons, the continental slope is slightly convex to linear with a gradient of about 5?-6?. Canyon walls commonly slope at 15?-22?. The passive continental margin narrows to 65-km at the Murray Canyons and links the Bight and Otway Basins. WNW-trending Jurassic-Cretaceous rift structures control the irregular shape of the central canyons. At the western end, large box canyons 1 km deep are incised into thick sediments of the Ceduna Sub-basin. Formed by headscarp erosion, some of these canyons have coalesced by canyon capture. The upper parts of most canyons are cut into Cretaceous sediments and in some places are floored by basement rocks. Large holes, spaced about 5 km apart and up to several hundred metres deep, along the outlet channels of the larger and steeper canyons were probably gouged by turbidity currents resulting from major slope failures at the shelf edge. Quaternary turbidites were deposited on the abyssal plain more than 100 km from the foot of slope. Canyon down-cutting was episodic since the latest Cretaceous, with peak activity since the Oligocene due to strong glacioeustatic fluctations and cycles, with canyon development occurring during lowstands and early transgressions when sediment input at the shelf edge was usually highest. The timing of canyon development is linked to major unconformities within adjacent basins, with down-cutting events recorded or inferred during early Paleocene, Middle Eocene, Early Oligocene, Oligocene/Miocene transition (~24 Ma), mid Miocene (~14 Ma) and latest Miocene-Pleistocene. The early phases involved only siliciclastic sediments, while post-early Eocene canyon cutting was dominated by biogenic carbonates generated on the shelf and upper continental slope. The Murray River dumped its sediment load directly into Sprigg Canyon during extreme lowstands of the Late Pleistocene when the Lacepede Shelf was dry land.

  • The NSW Continental Slopes survey GA-2413, SS10/2006 was acquired by Geoscience australia onboard the RV Southern Surveyor from the 12th of October to the 25th of October 2006. The geographical range stretched from Jervis bay in the South to Port Stephens in the North. The aim was to assess the physical nature of the NSW continental slope, improve our understanding of the surface and subsurface structure of the continental slope and to investigate the history of sediment movement along the continental slope.

  • The Mentelle Basin survey GA-0293, SS08/2005 was acquired by Geoscience Australia onboard the RV Southern Surveyor from the 28th of September to the 19th of October 2005. This deep water rift basin (up to 4500m depth) is located offshore from Fremantle on the SW Australian margin. The objectives of the survey was to study deep water marine habitats and to assess the petroleum potential of the Mentelle Basin. The swath data collected covered a new area of seabed that revealed the extents of the blind submarine canyons and completed the coverage of the Perth Canyon and filled the remaining gaps with high resolution swath bathymetry data.

  • Geoscience Australia conducted a marine seismic survey (GA-0349) over poorly defined areas of the Houtman sub-basin (part of the Perth basin) between 15th of November to the 23rd of January 2015. The aim was to acquire high quality, industry-standard precompetitive 2D seismic data, Multi-beam echo-sounder (MBES) off the coast of Western Australia. The new seismic data will supplement existing geological knowledge of the region, underpin petroleum prospectivity evaluation and support the discovery of new oil gas resources.

  • The collection consists of seabed samples collected by Geoscience Australia and other organizations since the 1950s. Samples consist of various shallow cores types, rocks derived from dredging, and sea bed sediments collected by grab and dredge methods. A large proportion of samples are refrigerated.

  • 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: 1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay; 2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and 3. Collect tidal data for the survey area. 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. These datasets comprise total sediment metabolism, mineral specific surface area and carbonate and element concetrations, and C and N isotopes of seabed sediments. A detailed account of the survey is provided in: 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