This is a compilation of all the bathymetry data that GA holds in its database for the area that covers the Diamantina Fracture Zone to the Naturaliste Plateau. This dataset consist of different 6X4 degrees tiles that are: Tiles SI48,SJ48,SK48,SL48, SI47,SJ47, SK47,SL47, SJ46,SK46,SL46, SK45 and SL45)

Legacy product - no abstract available

Legacy product - no abstract available

This Bulletin presents the results of a marine geological survey carried out by BMR in the Arafura Sea in 1969 as part of a program of regional geological reconnaissance mapping of the Australian continental shelf. It is a continuation of work in the Timor Sea and northwest shelf (van Andel, Veevers, 1967; Jones, 1968, 1970). The area surveyed is the northern Australian continental shelf between longitudes 130° and 136°E and between latitudes 8° and 12°S (Fig. 1), an area of about 240 000 km-. From 2 to 25 May the Japanese research submersible Yomiuri and its mothership, the converted deepsea tug Yamato, were made available. The major part of the survey lasted from 21 September to 6 December 1969, using the chartered oil-rig supply vessel San Pedro Sound as a platform.

Geoscience Australia has recently completed a marine survey in the offshore northern Perth Basin, off Western Australia (Jones et al., 2011b; Jones, 2011c, Upton and Jones, 2011). One of the principal aims of the survey was the collection of evidence for natural hydrocarbon seepage. The survey formed part of a regional reassessment of the basin's petroleum prospectivity in support of frontier exploration acreage Release Area W11-18. This reassessment was initiated under the Australian Government's Offshore Energy Security Program and formed part of Geoscience Australia's continuing efforts to identify a new offshore petroleum province. The offshore northern Perth Basin was identified as a basin with new frontier opportunities. New data demonstrated that proven onshore-nearshore petroleum system is also effective and widespread in the offshore (Jones et al., 2011a). Evidence for a Jurassic petroleum system was also demonstrated in the Release Area W11-18 (Jones et al., 2011a). The marine survey results provide additional support for the presence of an active petroleum system in the northern Perth Basin.

The Capel and Faust basins lie at water depths of 1,500-3,000 m 800 km east of Brisbane. Geoscience Australia began a petroleum prospectivity study of these remote frontier basins with the acquisition of 2D geophysical data (seismic reflection, refraction, gravity, magnetic, multi-beam bathymetry) across an area of 87,000 km2 during 2006/07. The approach mapped the complex distribution of sub-basins and determined sediment thickness through integration of traditional 2D time-domain seismic interpretation techniques with 3D mapping, visualisation and gravity modelling. Forward and inverse 3D gravity models were used to inform the seismic interpretation process and test the seismic basement pick. Gravity models had three sediment layers with inferred average densities of 1.85, 2.13, 2.31 t/m3 overlying a pre-rift basement of density 2.54 t/m3, itself considered to consist of older basin material evidently intruded by igneous rocks. Conversion of travel times of interpreted seismic horizons to depth domain was achieved using a quadratic function derived from ray-tracing forward modelling of refraction data supplemented by stacking interval velocities, and densities for gravity modelling were inferred from the same velocity models. These models suggest sediment of average velocity 3.5 km/s reaches a thickness exceeding 6 km in the northwest of the area, and for the first time mapped the extent and depth of sediment in these basins. The results of the study have confirmed that sediment thickness in the Capel and Faust basins is sufficient in places for potential petroleum generation.

In 1998, Franklin Cruise FR11/98 recovered 18 dredge hauls in deep water in the Gippsland Basin. The dredge hauls were sited on the basis of seismic reflection profiles and morphological features. The study provided information on the lithologies, ages and paleo-environments of the little-known deepwater Gippsland Basin. The rocks and sediments fall broadly into four categories: volcanics of probable Late Cretaceous age, volcaniclastics and labile sediments of Late Cretaceous age, Neogene marly calcareous sediments, and calcareous oozes of the Quaternary to Holocene. Minor ferromanganese nodules and crusts from several deepwater stations are of no economic potential, being high in SiO2 and remarkably low in copper and cobalt. Volcanics were confined to the three easternmost dredges (present water depths 3300-3800 m) from a rifted block elongated west-northwest and just inboard of the continent-ocean boundary. They consist of basalt, hyaloclastite, breccia, scoria and volcaniclastic sandstone. Because, these volcanic rocks occur on an isolated ridge they cannot have derived pebbles and clasts from younger sequences. The rocks are not dated but may have been laid down during the Tasman Sea rifting phase in the Turonian to Coniacian. We hypothesise that lava flows and domes formed on a coastal plain and in shallow water. Normal vesicular flows formed on dry land, and some weathered to scorias. In water they broke up to form volcaniclastic mass flow deposits such as hyaloclastites. Some of the volcaniclastics apparently became intermingled with soft clays and lime muds, because the interstices are now filled with zeolites, clay minerals and calcite. No Early Cretaceous rocks (Strzelecki Group) age were recovered, suggesting that they were not deposited east of the Gippsland Rise (~149?30?E). Immature labile rocks of the Late Cretaceous (Emperor and Golden Beach Subgroups of the Latrobe Group) were recovered in eleven dredges on the outer continental margin (present water depths 800-2040m). Palynological ages are Turonian to Campanian (~90 Ma to ~74 Ma). Thin to medium bedded labile sandstone, siltstone and mudstone (and their weathered variants) are carbonaceous in part. Some beds are burrowed and mottled or contain cross-lamination, ferruginous nodules, trace fossils, load casts, ripple marks and plants. Marine macrofossils are generally absent. These rocks were apparently deposited rapidly in coastal and marine environments, in the rift involving eastern Australia, Lord Howe Rise, and the Gippsland Basin. Palynology documents the onset on marine conditions, and rapid subsidence between ~90 Ma and ~86 Ma, as the Tasman Sea entered. Silts and clays were deposited in a deep freshwater lake in the Early to mid Turonian, deep marine carbonates in the Santonian, and deep marine muds in the Campanian. Marine calcareous rocks of the post-Eocene Seaspray Group were recovered in eight dredges (present water depths 680-2800 m): medium to very fine grained calcarenites, calcisiltites and calcareous mudstones, composed largely of molluscan debris, foraminifers and clay. They are often poorly bedded, with some thin to medium bedding. Quartz, feldspar, clay clasts and muscovite are common. Mottling shows that bioturbation was widespread, and organic debris includes wood and leaves, sponge spicules and echinoderm spines. Foraminifera date the older rocks as early to middle Miocene. Microplankton indicate deep-water deposition.

Overall, the cruise met its objectives of studying rift and drift sedimentation, and obtaining cores for palaeo-oceanography. The east Tasmanian seismic program was completely successful. The planned sampling program was somewhat curtailed by bad weather, equipment failures and other factors. It was least successful off east Tasmania. A total of about 1300 km of 8-fold multichannel seismic data were acquired along 8 transects across the east Tasmanian margin. The quality of the seismic profiles was excellent, with good resolution and penetration, given the bad weather and the limitations of the acquisition system. The seismic source comprised 2 GI airguns (each 45/105 cu. in. capacity) giving a penetration of 2-2.5 s twt (2.5-3 km) in places. The seismic profiles indicate a structurally complex margin with rugged basement relief that includes large-scale horst/graben structures and volcanic intrusions. The sedimentary section on the continental slope is at least 1.5 s twt thick in some graben and includes Campanian-Paleocene early sag-phase deposits, which are 0.5-1.0 s twt thick. Regional compressive tectonism in the Late Paleocene-Early Eocene has produced widespread inversion (folding/faulting) in this succession. A wedge of Neogene shallow-water carbonates underlies the continental shelf. It shows seaward progradation and attains a maximum thickness of ~700 m beneath the shelf edge. Oceanic basement (?Campanian) adjacent to the margin lies at a depth of 7.0-7.5 s twt. The continental rise and Tasman Abyssal Plain in this zone are underlain by 1.5-2.0 s twt of post-breakup sedimentary section. The East Tasman Saddle is underlain by `transitional? basement and contains a sedimentary section of similar thickness. During the sampling program 58 of 86 stations were successful: 38 gravity cores (21 successful), 4 piston cores (3), 16 dredges (7) and 28 grabs (28). Total core recovery was 81.4 metres from the 16 successful cores taken in soft sediments, an average recovery of about 5 metres. The fairly low success rate with the gravity corer can be ascribed to problems with foram sand east of Tasmania, and shelly sand in Storm Bay. The low success rate with the dredge was related to the lightness of the gear. The deployment of the heavy piston corer for the first time on Franklin was successful. However, we did not attempt to piston core in deep water. East of Tasmania we recovered 8 gravity cores, and 7 dredge hauls. Deepwater dredging and coring were surprisingly unsuccessful. The upper slope stations, designed to sample older rocks, were reasonably successful. From these results and some existing information, general conclusions can be drawn about changes along the margin with increasing water depth. The shelf and upper slope wedge of Neogene, seaward-prograding sediments was sampled out to 1640 m. The sediments recovered include muddy sand, clayey sandstone with siliceous nodules, siliceous sandstone and calcarenite. The calcarenite is presumably part of the Middle Miocene shelf limestone sequence that is widespread off St Helens. Somewhat deeper on the upper slope, basement outcrops occur in steep slopes: granite, arkose, metasediments, conglomerate, quartz sandstone and gritty mudstone. The granites are probably from Devonian batholiths like those onshore up the east coast. Volcanic rocks and conglomerate form a basement block in deeper water on a ridge off northeast Tasmania at ~3750m. Deepwater outcrop ridges support manganese nodules and crusts. Nannofossil oozes cling to the slope, particularly in local basins, and are ubiquitous in deep water. The East Australian Current apparently winnows many of the oozes to form a blanket of foram sand.

The RV Franklin sailed from Brisbane on 17th January 2002 and returned to Cairns on 9th February, 2002. The cruise discovered that a zone of strong tidal currents at the northern end of the Great Barrier Reef prevents the southward advance of sediment that would otherwise bury the coral reefs. The Fly River, located in close proximity to the northern end of the Great Barrier Reef, discharges about 120 million tonnes/yr of sediment. This sediment does not penetrate as far south into the reef area as might be expected because, over glacial-interglacial cycles of sea level change, the southward-prograding deposits are eroded by tidal currents. Deployment of an instrumented current meter and suspended sediment measurement frame on the seabed, offshore from the Fly River Delta, recorded a net sediment advection southwards. Sediment transport was greatest following a northerly wind event, which caused high bottom stress and increased turbidity levels. Swath sonar mapping and underwater video equipment were used to map a series of channels up to 220 m deep extending from eastern Torres Strait across the northern end of the Great Barrier Reef. Channels in the north are clearly relict fluvial channels, exhibiting lateral accretion surfaces and incised channels that intersect and truncate underlying strata. Over-deepened channels in the south, however, appear to have formed by tidal current scour. They exhibit closed bathymetric contours at both ends and are floored with well-sorted carbonate gravely sand. Oceanographic observations indicate that the channels provide a conduit onto the shelf for up-welled Coral Sea water. The deepest channels form isolated depressions, and possibly were the sites of lakes during the last ice age. Preliminary modelling indicates that the strongest tidal currents occur when sea level is about 40m below present, suggesting that the channels are Pleistocene or older in age and of relict origin.

Geoscience Australia Marine Survey 267 was undertaken aboard the Parmelia K, a 28 m pearling boat out of Broome. The survey departed Darwin on 3 March 2004 and terminated in Broome on 18 March 2004. The length of the survey was curtailed by unfavourable weather conditions associated with tropical cyclones Evan and Fay. The aim of the survey was to test and validate a range of techniques used in the detection/identification of natural hydrocarbon seepage. The Yampi Shelf in the northern North West Shelf was selected for the test bed as it is a known region of intense and widespread hydrocarbon seepage. One of the most significant findings of the survey was the direct observation of natural hydrocarbon seepage in the Timor Sea region of the North West Shelf, which has previously only been interpreted through remote sensing or automated water sampling techniques (sniffer). Seepage plumes were observed rising from pockmark fields or hard-grounds on the vessel's echosounder and the side-scan sonar. Gas bubbles with oily films were observed at the surface. Active seepage sites were detected in close associated with hydrocarbon related diagenetic zones (HRDZs) interpreted in 3D seismic coverage of the region. A towed fluorometer detected variations in the hydrocarbon concentration of the sea surface over the study areas. Seepage appeared to be most active in association with low-tide, and more suppressed during high tide. Multi-beam swath bathymetry of the study areas revealed channels between 2 and 20 m deep on the Yampi Shelf headland and in the vicinity of the major HRDZs. Tidal current directions measured by an acoustic doppler current profiler (ADCP) in the Yampi Shelf headland channels suggests that tidal shears over this headland may be giving a response on Synthetic Aperture Radar (SAR). Sediment samples were collected with a Smith-Macintyre Grab, a dredge and a gravity core, although coring was largely unsuccessful due to carbonate hard-grounds over the seepage sites. Grab and dredge samples suggest that the active seeps are zones of preferential macro-biotic distribution. Significant down-time was introduced through poorly functioning equipment and a lack of experience on behalf of the staff. This was primarily due to the fact that some of the equipment was leased from Seismic Asia Pacific Ltd. Therefore it is recommended for future surveys that an operator be supplied with leased equipment, or that the equipment is purchased by Geoscience Australia and staff are appropriately trained before the survey. It is also highly recommended that the survey have seismic acquisition capability, as the seismic data proved to be the best proxy for seepage site location.