The Davis Coastal Seabed Mapping Survey, Antarctica (GA-4301 / AAS2201 / HI468) was acquired by the Australian Antarctic Division workboat Howard Burton during February-March 2010 as a component of Australian Antarctic Science (AAS) Project 2201 - Natural Variability and Human Induced Change on Antarctic Nearshore Marine Benthic Communities. The survey was undertaken as a collaboration between Geoscience Australia, the Australian Antarctic Division and the Australian Hydrographic Service (Royal Australian Navy). The objectives were to provide multibeam bathymetry and backscatter of the coastal region of the Vestfold Hills around Davis Station, Antarctica, to aid the understanding of sea bed character, benthic habitats, provide a basis for hydrodynamic modeling of water movement around Davis, and to update and extend the navigational charts of the region.

This map has been created to update the old Crimes at Sea maps produced in 2000. These maps have been checked & approved by the Attorney Generals Office April 2013. There are 13 maps in the series plus the main map showing all of the Australian Territory. The AAT maps have not been released to the public as yet. Located in M:\Products\Australias Crimes Act Offshore Areas\products

Studies utilising high-resolution multibeam swath bathymetry datasets to understand the glacial evolution of the previously glaciated Antarctic continental margin are limited, and are particularly meagre for the East Antarctic Continental shelf. Here we present an interpretation of the seafloor geomorphology based on a new swath bathymetry dataset from the shallow-water marine environment of the Windmill Islands, adjacent to the Australian Antarctic research station, Casey. This high resolution (1 m) dataset permits visualisation of geomorphological features preserved on the seafloor in unparalleled detail. The seafloor is dominated by an assemblage of bedrock, glacial and post-glacial features, providing new insight into the behaviour of the ice-sheet in the region during past glacial episodes and its subsequent retreat to present-day conditions. Interpretation of the submarine geomorphology reveals five dominant features: (1) basement fault systems and bedrock `highs (2) meltwater channels, (3) streamlined sub-glacial landforms, (4) moraine ridges and (5) isolated basins and depressions. Distinctive NW-SE trending channels and linear features that represent brittle bedrock fault systems are clearly evident. These sub-parallel basement bedrock faults or joints have been preferentially eroded and widened by glacial action to form narrow channels and preserve typical `U-shaped profiles. A secondary set of SW to WSW trending linear features are characterised by broad eroded channels. The general orientation of the coastline and channels in the region suggest that these linear features fundamentally control the regional coastal and seafloor geomorphology. Regions of bedrock highs, comprised of submarine outcrops of crystalline metamorphic basement, are characterised by complex, rugged and variable topography, forming steep knolls, small shoals and reefs. Numerous channel networks have been incised into crystalline bedrock highs and their meandering nature, orientation and geometry are consistent with meltwater channels formed by subglacial hydrological flow under considerable hydrostatic pressure. They likely formed during a period when the ice-sheet was expanded and grounded over the areas of offshore crystalline bedrock, possibly during the late Pleistocene Glacial Maximum (LGM) or earlier glaciations. Glacial lineations characterised by subdued sub-parallel linear ridges are preserved in basins and appear to have formed from moulding of unconsolidated sediments by overriding ice. The orientation of the lineations are consistent with formation during westward expansion of the Law Dome ice-sheet onto the continental shelf during the LGM. Regular and closely-spaced arcuate moraine ridge sets are preserved mostly within the prominent NW-trending U-shaped channels. These features appear to be a sequence of recessional moraines or push moraine banks recording slow or episodic retreat of channelized valley glaciers or outlet ice-streams which appear strongly controlled by the local bathymetry. There are several enclosed basins and shallow depressions between bedrock highs with varying degrees of post-glacial sedimentary infill. There is little evidence of reworking of sediments by currents and as a result, the glacial features in this dataset are well preserved. Interpretation of submarine glacial landforms using high-resolution swath bathymetry, integrated with existing information of local ice-sheet evolution from terrestrial studies, allows us to enhance our understanding of the ice-sheet dynamics in the Windmill Islands region.

Integration of conventional interpretation of deep-seismic data with potential field modelling is a powerful tool for elucidating the geology of continental margins and particularly the continent-ocean transition zone (COT). Recent work carried out on the Wilkes Land margin of East Antarctica using new seismic and potential field data shows the power of combining these techniques. In this study, the initial deep-seismic interpretation was combined with sonobuoy- and stacking-derived velocity information to provide a starting model for the potential field modelling; the potential field model and aspects of the seismic interpretation were iterated until a consistent interpretation was reached. The most important observations from the COT zone on the Wilkes Land margin include: ? The outer edge of the COT, that is the point at which the crustal type becomes 100% oceanic, is much further offshore than previously interpreted from seismic data and seafloor spreading anomalies, and lies beneath the deep ocean basin. ? The COT is dominated by a basement ridge complex which may represent serpentinised, unroofed mantle peridotites and associated intrusions and extrusions related to decompression melting, similar to features inferred on the conjugate southern Australian margin. ? The lower crust is inhomogeneous, probably due to massive localised intrusion landward of the COT; however, pre-existing inhomogeneities cannot be ruled out. ? The base of the crust has considerable relief landward of the COT, increasing from ~10 km to 16 km depth over a distance of about 40 km.

New deep-seismic data acquired from offshore East Antarctica by Australia provide more than 40 crossings of the continent-ocean transition (COT) along the 5500 km length of the continental margin that was formerly adjacent to the east coast of India and the southern margin of Australia prior to East Gondwana breakup. As volcanic activity is relatively subdued on this margin, except in the vicinity of the southern Kerguelen Plateau, the data provide a window into the late-rift and post-rift stages of formation of a non-volcanic rifted margin. Three characteristic margin segments are interpreted in the data. From west to east, these are: Offshore Enderby Land to Prydz Bay (38-80oE): The COT is not clearly defined in this zone, probably due in part to the effect of the Kerguelen hot spot in the Late Cretaceous. Delineation of the COT here will rely heavily on potential field modelling. Queen Mary Land 90-105oE): southeast of the Kerguelen Plateau, the margin is dominated by Bruce Rise, a continental marginal plateau that was formerly conjugate to the Naturaliste Plateau off southwest Australia. The transition from continental to oceanic crust is sharp, in apparent contrast to the conjugate margin off southwest Australia. Wilkes Land (105-140oE): in the area formerly conjugate to southern Australia, the margin is characterised by a broad zone of deeply-subsided continental and transitional crust beneath the inner edge of the deep ocean basin in an area previously considered to have been oceanic crust formed by seafloor spreading.

This abstract outlines the interpretation of geophysical data acquired by the Australian Antarctic and Southern Ocean Profiling Project in the offshoree AAT, southwest of the Kerguelen Plateau.

Deep-seismic data acquired by Geoscience Australia from the Naturaliste Plateau off southwest Australia in 1997, and from Bruce Rise on the margin of East Antarctica in 2001, allow direct comparison of these conjugate margins for the first time. Sampling has shown that the Naturaliste Plateau is at least partly of continental origin and composed of Proterozoic to Cambrian metamorphic rocks. A rift phase on the Naturaliste Plateau resulting in a series of predominantly E-W oriented grabens is estimated to have occurred in the Late Jurassic to earliest Cretaceous. Similar grabens are also present beneath the Bruce Rise. The Diamantina Zone, south of the Naturaliste Plateau, has been interpreted as a continent-ocean transitional zone with sampling indicating that the southernmost part is comprised of peridotite ridges. In contrast, to the north and northwest of Bruce Rise, the basement seismic character, and headwave velocities interpreted from sonobuoys, suggest that it is likely to be of oceanic origin. This crust lies about 2000 m deeper than the fast-spreading Eocene crust of the Australian-Antarctic Basin. Correlation of magnetic anomalies and the seismic character of the deep crust suggest that it formed either during an episode of Early Cretaceous seafloor spreading coincident with the opening of the Perth and Enderby Basins, rather than during the very slow spreading between Australia and Antarctica that started in the early Campanian. In either case, the breakup of the Naturaliste Plateau and the Bruce Rise appears to have been highly asymmetric with most of the extended continental or transitional crust being attached to the Australian margin.

This abstract contains a summary of the broad scientific results coming out of the interpretation of data acquired under the Australian Antarctic & Southern Ocean Profiling Project.

Legacy product - no abstract available

Seismic reflection data show the existence of two major sedimentary basins along the continental margin of Wilkes Land and Terre Adélie, East Antarctica, that contain more than 5 s TWT (> 9 km) of sediments. Four seismic megasequences are identified (MS4 to MS1) that are bounded by: basement, unconformities of interpreted Turonian, Maastrichtian and early Middle Eocene age, and the seafloor. The 4-5 km thick rift and pre-rift sediments are concentrated in a margin-parallel basin (Sabrina Basin). On the basis of seismic correlation with the Australian margin, this basin is interpreted to be of Late Jurassic to mid-Cretaceous age. The post-rift sediments are generally thick along the margin and in the adjacent deep-ocean basin, but are particularly thick in a major depocentre off west Wilkes Land, named here the Budd Coast Basin (BCB). The BCB contains a maximum observed thickness of 5 s TWT (9 km) of post-rift sediments and its location suggests that the sediments were largely derived from a sub-glacial basin currently occupied by the Totten Glacier.