From 1 - 10 / 1822
  • 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.

  • Total magnetic intensity data measures variations in the intensity of the Earth's magnetic filed caused by the contrasting content of rock-forming minerals in the Earth's crust. The data are collected on airborne geophysical surveys conducted by Commonwealth, State & NT Governments and the private sector.

  • Records of abstracts from the Annual Geoscience Exploration Seminar (AGES) 2005

  • 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.

  • Gravity data measures small changes in gravity due to changes in the density of rocks beneath the Earth's surface. The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This Paterson_Complete_Bouguer_1VD.nc grid is a first vertical derivative of the Bouguer anomaly grid for the Paterson - WA Gravity survey. This gravity survey was acquired under the project No. 200560 for the geological survey of WA. The grid has a cell size of 0.0037 degrees (approximately 400m). A total of 4534 gravity stations were acquired to produce the original grid. A Fast Fourier Transform (FFT) process was applied to the original grid to calculate the first vertical derivative grid.

  • Gravity data measures small changes in gravity due to changes in the density of rocks beneath the Earth's surface. The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This Paterson_Complete_Bouguer.nc grid is a complete Bouguer anomaly grid for the Paterson - WA Gravity survey. This gravity survey was acquired under the project No. 200560 for the geological survey of WA. The grid has a cell size of 0.0037 degrees (approximately 400m). A total of 4534 gravity stations were acquired to produce this grid.

  • This web-enabled system allows researchers to retrieve fluid inclusion data from anywhere in the world. The concept is to build a free and widely available web-based library of fluid properties for a range of geological fluids. The database is being developed as an "open" project, which intends to bring together researchers interested in the properties of geological fluids or fluid inclusions.

  • This map is part of the series that covers the whole of Australia at a scale of 1:250 000 (1cm on a map represents 2.5 km on the ground) and comprises 513 maps. This is the largest scale at which published topographic maps cover the entire continent. Each standard map covers an area of 1.5 degrees longitude by 1 degree latitude or about 150 kilometres from east to west and 110 kilometres from north to south. There are about 50 special maps in the series and these maps cover a non-standard area. Typically, where a map produced on standard sheet lines is largely ocean it is combined with its landward neighbour. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours (interval 50m), localities and some administrative boundaries. The topographic map and data index shows coverage of the sheets. Product Specifications Coverage: The series covers the whole of Australia with 513 maps. Currency: Ranges from 1995 to 2009. 95% of maps have a reliability date of 1994 or later. Coordinates: Geographical and either AMG or MGA (post-1993) Datum: AGD66, GDA94, AHD. Projection: Universal Traverse Mercator (UTM) Medium: Paper, flat and folded copies.

  • This map is part of the series that covers the whole of Australia at a scale of 1:250 000 (1cm on a map represents 2.5 km on the ground) and comprises 513 maps. This is the largest scale at which published topographic maps cover the entire continent. Each standard map covers an area of 1.5 degrees longitude by 1 degree latitude or about 150 kilometres from east to west and 110 kilometres from north to south. There are about 50 special maps in the series and these maps cover a non-standard area. Typically, where a map produced on standard sheet lines is largely ocean it is combined with its landward neighbour. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours (interval 50m), localities and some administrative boundaries. The topographic map and data index shows coverage of the sheets. Product Specifications Coverage: The series covers the whole of Australia with 513 maps. Currency: Ranges from 1995 to 2009. 95% of maps have a reliability date of 1994 or later. Coordinates: Geographical and either AMG or MGA (post-1993) Datum: AGD66, GDA94, AHD. Projection: Universal Traverse Mercator (UTM) Medium: Paper, flat and folded copies.

  • This map is part of the series that covers the whole of Australia at a scale of 1:250 000 (1cm on a map represents 2.5 km on the ground) and comprises 513 maps. This is the largest scale at which published topographic maps cover the entire continent. Each standard map covers an area of 1.5 degrees longitude by 1 degree latitude or about 150 kilometres from east to west and 110 kilometres from north to south. There are about 50 special maps in the series and these maps cover a non-standard area. Typically, where a map produced on standard sheet lines is largely ocean it is combined with its landward neighbour. These maps contain natural and constructed features including road and rail infrastructure, vegetation, hydrography, contours (interval 50m), localities and some administrative boundaries. The topographic map and data index shows coverage of the sheets. Product Specifications Coverage: The series covers the whole of Australia with 513 maps. Currency: Ranges from 1995 to 2009. 95% of maps have a reliability date of 1994 or later. Coordinates: Geographical and either AMG or MGA (post-1993) Datum: AGD66, GDA94, AHD. Projection: Universal Traverse Mercator (UTM) Medium: Paper, flat and folded copies.