Legacy product - no abstract available

Legacy product - no abstract available

This map shows the boundaries of the security regulated port for the purpose of the Maritime Transport & Office Security Act 2003. 3 sheets (Colour) December 2008 Not for sale or public distribution Contact Manager LOSAMBA project

This map shows area of the West Coast Tasmania Shark Gillnet and Shark Hook Sector 130m Depth Commonwealth Closure. Modified from GeoCat 65105 (2007) as per the Southern and Eastern Scalefish and Shark Fishery (Closures) Direction No. 1 2009 - Schedule 14. Produced for the Australian Fisheries Management Authority. Not for public sale or distribution by GA.

Legacy product - no abstract available

Special demagnetising apparatus was constructed to study the stability of several samples of basic igneous rocks from three localities in eastern Australia, particular emphasis being placed on the reliability of the directions of NRM. The direction of primary magnetisation acquired when the rocks first cooled was determined for samples at all three sites. Mesozoic dolerite from Red Hill Dyke in southern Tasmania has little or no secondary magnetisation and the mean direction of NRM is representative of the Jurassic in Tasmania. There is no evidence of systematic error due to stress or shape, and therefore the direction of NRM is a reliable estimate of the direction of the geomagnetic field at the time of intrusion. Devonian Nethercote basalt from southern New South Wales can be divided into two distinct groups, one in which the NRM is completely unaffected in either direction or intensity by demagnetisation in peak alternating fields of up to 1000 oersteds, and the other in which secondary magnetisation completely masks any primary magnetisation that may be present. Tertiary basalts from southern New South Wales show a wide range of stability. The NRM consists of primary TRM and varying proportionate amounts of secondary magnetisation, which is almost certainly viscous and which was probably acquired in the present Earth's field. The stability shown by the three rock types makes it more probable that previous palaeomagnetic results, which span a long period from Devonian to Tertiary, form a reliable record of the geomagnetic field in Australia.The general effects of alternating demagnetising fields are also discussed and a comparison made between the theoretical predictions and the data obtained.

Legacy product - no abstract available

Legacy product - no abstract available

22-1/K55-6/1

Deep seismic reflection profiles collected offshore during a circum-navigation of Tasmania have provided fundamental information on the crustal architecture of the State. In particular, the profiles show the geometry of the boundaries between the major crustal elements, including the offshore continuation of the Arthur Lineament. These crustal element boundaries have apparent dips to the east or southeast and most of them appear to cut through the entire crust to the Moho. In eastern Tasmania, the seismic lines show an old mid-crustal extensional event followed by crustal shortening and duplexing, which probably occurred during the Cambrian-Ordovician Delamerian Orogeny. Thrusts that developed at this time were later reactivated as extensional faults during continental breakup of Pangea in the Cretaceous. Granites off the west coast have the geometry of flat, thin pancakes. In summary, the offshore seismic reflection program around Tasmania has led to a better understanding of the geometry and relationships between the basement elements of Tasmania and younger basins.