This report presents the results of a regional seafloor mapping study carried out during 2000/2001 as part of Geoscience Australia's South and Southwest Regional Project. The aim was to support future Regional Marine Planning in the Great Australian Bight (GAB) by underpinning biological, environmental and economic assessments with basic information on geomorphology and the seabed character. Four major geomorphological features are present on the margin in the South and Southwest (SSW) region: a continental shelf, marine terraces (including the Eyre and Ceduna Terraces in the GAB), a continental slope and a continental rise. The boundaries of these geomorphological features have been delineated and captured in a Geographical Information System (GIS). The GIS also includes the location of sedimentary basins, plateaus, terraces and canyons previously mapped in the region. Seabed character mapping was carried out for the GAB area only. Five echo facies have been defined in the GAB area based on the interpretation of available 3.5kHz echo-sounding records and high-resolution seismic profiles in terms of acoustic facies, and their groundtruthing against seafloor samples. The interpretation of these facies has been digitised and captured into a GIS. The GIS includes key attributes for every echo facies. The acoustic facies distribution on the GAB margin and offshore in the South Australian abyssal plain shows the importance of geological inheritance to the geomorphology and sea-bed character of the region. Facies I, which represents undisturbed, layered sediments is mainly localised on the shelf, the Eyre and Ceduna Terraces, and in the greater part of the abyssal plain. Facies II, which may represent more disturbed sediments, is confined to the Ceduna Terrace and along two elongated E-W trending areas on the abyssal plain near the continent-ocean boundary. Facies III, associated with extreme (IIIA), moderate (IIIC) and low (IIID) topography, underlies scarps, canyons, and depressions on the continental slope and the abyssal plain. The distribution of acoustic facies from the upper slope down to the abyssal plain indicates that the major sedimentary process in the deep water GAB is deposition of pelagic sediments. Reworking of sediments by both bottom currents and gravity flows is probably limited to submarine canyons.

In 1997, AGSO - Geoscience Australia (GA) and the Tectonics Special Research Centre (TSRC) at the University of Western Australian (UWA) and Curtin University conducted a joint research project to image the crustal setting of the Hamersley Province of northern Western Australia. This joint research was aimed at investigating the shallow structure of the Hamersley Province, the regions deeper basement structure and in so doing, developing an understanding of the region's tectonics and possible fluid migration pathways. The project's objectives were to obtain a better understanding of sub-surface geology of the Hamersley Province at both a regional scale and a mine scale. In particular, the project's objectives were to provide more information on: * regional crustal thickness and major features, * stratigraphic architecture of the regions mineral system, * structural architecture of the mineral system, * timing and locations of fluid migration pathways The seismic survey obtained 132 km of nominally 10 fold CMP (common midpoint) deep reflection seismic data along two transects over approximately 5 weeks of acquisition.

Legacy product - no abstract available

Londonderry - Drysdale TMI (rtp) with northeast illumination

This paper describes the highlights of AGSO's work in the North Pilbara Project, a joint AGSO-Western Australia Geological Survey (GSWA) effort conducted under the National Geoscience Mapping Accord (NGMA) between 1995 and 2000. One of the principal drivers for AGSO's research in the Pilbara was the possible inapplicability of exploration models and genetic interpretations of Archaean mineral deposits because these models were commonly based upon late Archaean examples. One of our goals was to document the differences between the late Archaean and the early-mid Archaean mineral systems, and to develop regional thematic synthesis datasets so that more robust models could be developed to encompass the entire Archaean era. These datasets, together with our research into new exploration tools, have, and continue to assist exploration in the Pilbara. Our results also have applications to other terranes.

The report summarises earthquake and tsunami information worldwide in 1997 but with a focus on Australia for use by scientists, engineers and the public. Maps of the seismicity are presented on a state-by-state basis and isoseismal maps are included for the significant earthquakes.

During 2000/2001 a new automatic method of merging gridded airborne magnetic data was developed by Geoscience Australia. This involves considering all the grids at once, and treating the requirement that they match together in the best possible way as a single inverse problem. Both `DC' and low-order polynomials can be applied to grids during the process. The program Gridmerge undertakes these tasks, as an independent entity within the Intrepid geophysical processing system. Regional compilations of airborne magnetic data (from the Yilgarn area of Western Australia, the Tanami-Arunta area of the Northern Territory, the Curnamona region of South Australia and New South Wales and all of Western Australia) are used to compare the results of Gridmerge with the test datasets.

Gravity surveys are used to measure small changes in the Earth's gravity field. These changes are due to density variations in the Earth's crust and can be used for a range of investigations such as studies of deep tectonic structures or finding caves in urban engineering studies. The physical property being measured, density variation, is the same in these investigations; it is just the survey parameters and precision required that differ. This manual serves to give a brief outline of the theory behind gravity surveying and discusses the considerations that need to be addressed when conducting gravity surveys. Gravity survey design and field techniques are discussed including both gravity and positioning equipment. Survey reduction and processing techniques are also discussed. This manual is not a definitive text on gravity surveying but rather a guide to techniques that have proved to be successful. As such, it is hoped it will be updated as techniques and instrumentation improve. Feedback or suggestions are welcome.

No abstract available

No abstract available