Victoria Coast 2007-2008

Multichannel seismic data collected off Wilkes Land (East Antarctica) reveal four main units that represent distinct phases in the evolution of the Cenozoic depositional environment. A Cretaceous synrift succession is overlain by hemipelagic and distal terrigenous sequences deposited during Phase 1. Sediment ridges and debris-flow deposits mark the transition to Phase 2. Unit 3 records the maximum sediment input from the continent and is characterized by the predominance of turbidite deposits. During Phase 4 the sediment supply from the continental margin was reduced, and draping and filling were the dominant processes on the continental rise. Unit 4 also contains the deposits of sediment wave fields and asymmetric channel-levee systems. These four units are a response to the Cenozoic evolution of the East Antarctic Ice Sheet. During Phase 1, small ice caps were formed in the innermost continental areas. The ice volume increased under temperate glacial regimes during Phases 2 and 3, when large volumes of melt-water production led to high sediment discharge to the continental rise. Change to a polar regime occurred through Phase 4, when a thick prograding wedge developed on the continental shelf and slope and the sediment transport to the rise diminished, producing general starvation conditions.

The question as to whether geophysical data from habitats can be used to predict the occurrence of benthic biodiversity is becoming more important with the increase in the use of Marine Protected Areas as tools for marine conservation. To help answer this question and to better understand the relationship between sediment, geomorphology and benthos, a multibeam sonar survey was conducted over two areas in the northern Great Barrier Reef - Gulf of Papua region. View this article in Geological Association of Canada Special Publication 47 pp. 247-263

Historically the emphasis on unraveling the structural geodynamic history of the Eastern Goldfields Superterrane of the Western Australian Yilgarn Craton has been on compression. A systematic study of: structural overprinting relationships; links with the rock record and architecture, reveals extension has been the dominant tectonic mode of the geodynamic history of the Eastern Goldfields. Extension was associated with: the deposition of the greenstone sequence; the emplacement of voluminous granites; the onset of Au mineralisation; dextral trans-tension and subsequent orogenic collapse. While compression or transpression structures host the majority of Au mineralisation these events are restricted to short protracted periods of time.

Paper supporting presentation of the 2007 Offshore Petroleum Explroation AReas at the Australian Petroleum Production and Exploration Association (APPEA) Conference, Adelaide, 16th April 2007.

It is shown how a change in orientation between the source mechanism of two identically located double couple sources can be estimated from the correlation of the coda waves excited by their sources. The change in orientation is given by the root mean square of the change in strike, ??s dip, ?? and rake, ?? of the double couple. It is not possible to determine ??s, ?? or ?? individually from the cross correlation. Applicability of the theory is tested using synthetic waveforms generated from a 3D finite difference solver for the elastic wave equation. Changes in strike, dip and rake are tested independently and simultaneously. In each case a crossover point is identified such that the actual change in orientation is within one standard deviation of the coda wave interferometry (CWI) estimates for all rotations below the crossover. After the crossover, the CWI estimates give a lower bound on the change in orientation.

Zircons within the Eocence Garford Paleochannel, central South Australia, were derived from two main sources: (1) local Archean-Mesoproterozoic rocks of the Gawler Craton exposed within the paleocatchment, including the 2525-2440 Ma Mulgathing Complex and 1595-1575 Ma Gawler Range Volcanics-Hiltaba Suite, and (2) Phanerozoic sedimentary rocks within the catchment that contribute a late Mesoproterozoic to Cretaceous component of recycled zircons from a variety of primary sources. These sources include the 1190-1120 Ma Pitjantjatjara Supersuite and 1080-1040 Ma Giles Complex, within the Musgrave Province; c. 510 Ma syn-Delamerian magmatism possibly derived from the Adelaide Rift Complex; and Jurassic-Cretaceous zircons ranging from ~220 Ma to ~100 Ma, with one statistical population at 122 ± 3 Ma. It is likely that zircons from these sources outside the paleocatchment were transported into the Mesozoic rocks of the Eromanga Basin within the catchments, before being re-eroded into the Garford Paleochannel. Given the presence of significant gold mineralization within the Neoarchean rocks of the Gawler Craton, the abundance of locally-derived Archean zircons may support the potential for paleoplacer gold deposits within the Eocene paleodrainage system. Likewise, the abundance of zircons derived from the Gawler Range Volcanics/Hiltaba Suite may support the notion that potential secondary uranium mineralisation within the paleochannels may have a source in these commonly uranium-enriched Mesoproterozoic volcanics and granites. Finally, these data suggest that the Garford Paleochannel was not a major contributor to the zircon budget of the paleo-beach heavy mineral sands province of the adjacent Eucla Basin.

A '10 slide presentation' on the transportation of uranium. It will be converted to a short movie with text overlays.

Close up map of Submarine Cables and southern protection zone around Clovelly / Tamarama, Sydney. For internal use by ACMA. Included in this version is The Peak Anchoring Zone and 1000 metre Offshore Line. This map developed from previous map GeoCat 64812 (June 06) and GeoCat 65103 (Feb 2007).

The Early Permian to Middle Triassic Bowen and Gunnedah basins in eastern Australia developed in response to a series of interplate and intraplate tectonic events located to the east of the basin system. The initial event was extensional and stretched the continental crust to form part of the major Early Permian East Australian Rift System that stretched at least from far north Queensland to southern New South Wales. The most commercially important of the rift-related features are a series of half graben that form the Denison Trough, now the site of several producing gas fields. The eastern part of the rift system commenced at about 305 Ma and was volcanic dominated. In contrast, the half graben in, and to the west of, the Bowen Basin were non-volcanic, and appear to have initiated at about 285 Ma. These half graben are essentially north-south in length with an extension direction of approximately east-northeast. Mechanical extension appears to have ceased at about 280 Ma, when subsidence became driven by thermal relaxation. The extension occurred in a backarc setting, in response to far field stresses that propagated from the west-dipping subduction system at the convergent plate margin of East Gondwana that was located to the east of the East Australian Rift System.