Ashmore Reef is an ovoid, shelf edge, platform reef located on the north west shelf of Australia (~ 12? 20? S, 123? 00? E) at the north-western boundary of the Browse and Bonaparte basins. Built on antecedent topography, it is the largest emergent reef with the highest biodiversity in the region. Geomorphological expressions of the carbonate platform include three vegetated cays with a sub-surface fresh water lens, guano deposits and beach rock, two lagoons separated by an calcareous algal rise, large scale mobile inter-tidal and sub-tidal sand flats, extensive lineated reef flats up to 1.7 km wide, an algal dominated reef rim rise, and a precipitous reef front with classical spur and groove morphology. Sedimentological analysis shows that the modern sand accumulations are primarily foraminifera, coral, molluscan fragments and a range of coralline algae (mainly Halimeda sp). The reef is subject to a 4.75 m semi-diurnal tide and lagoonal water temperatures range between 25.2 and 35.4?C. The climate is tropical monsoonal, and warm to hot, with the annual mean temperature at 28.5?C. Regional data indicate that rainfall exceeds 950 mm, and evaporation potential is 1820 mm. Dominant SW trade winds drive the surface currents and these interplay with the Indian Ocean and are seasonally influenced by southward moving Indonesian-Though-Flow waters. Thunderstorms occur on ~ 85 days in the wet season and the region experiences 7% of the global annual total of cyclones.

A seabed mapping survey over a series of carbonate banks, intervening channels and surrounding sediment plains on the Van Diemen Rise in the eastern Joseph Bonaparte Gulf was completed under a Memorandum of Understanding between Geoscience Australia and the Australian Institute of Marine Sciences. The survey obtained detailed geological (sedimentological, geochemical, geophysical) and biological data for the banks, channels and plains to establish the late-Quaternary evolution of the region and investigate relationships between the physical environment and associated biota for biodiversity prediction. This report provides details of the activities undertaken during the (survey SOL4934), including a list of the samples and data that were collected. The survey was completed between 27 August and 24 September, 2009.

High resolution multibeam bathymetry is used to map and interpret seabed geomorphology for part of the northern Lord Howe Rise plateau in the Tasman Sea. A mapping system of geomorphic units and elements is used, extending the previous hierarchy of geomorphic provinces and features used for the Australian margin. The mapped area covers ~25,500 km2 and incorporates broad ridges, valleys and plateaus. Superimposed on these features are clusters of volcanic peaks, smaller ridges, holes, scarps and aprons. An additional characteristic of the seabed in this area is an extensive network of polygonal furrows that cover the plateaus and the lower slopes of larger ridges. These furrows are formed in stiff, unconsolidated carbonate ooze that forms a near-continuous sediment cover across the area. Peaks are the only geomorphic feature not fully draped in pelagic ooze. The distribution of geomorphic units suggests strong controls from underlying geological structures. In water depths of 1400 m to 1600 m some peaks occur in clusters on ridges that sit above acoustic basement highs and volcanic intrusions. Elsewhere, broad plains and valleys slope to the southwest following the regional dip of the Lord Howe Rise plateau. In contrast, localised geomorphic elements such as moats and holes have likely explanation in terms of spatial variations in sedimentation rates in relation to bathymetric highs. Polygonal furrows are attributed to dewatering processes. The geomorphology of the seabed mapped in this study incorporates examples of forms that have not been previously mapped in such detail on the Australian margin. These are unlikely to be unique to the mapped area of the Lord Howe Rise and can be expected to occur elsewhere on the Rise and presumably on other parts of the Australian margin with a similar geological history.

Legacy product - no abstract available

Legacy product - no abstract available

These data were derived from the Australian Bathymetry database held at Geoscience Australia. The dataset comprises depth, seabed morphometric parameters: slope, aspect, topographic relief and rocky layer, and geomorphic features.

Positioned at the transition zone of the major hydrocarbon provinces of Browse and Bonaparte Basins, Ashmore Reef is built on what is thought to be Pleistocene antecedent topography. This mature, ovoid, shelf-edge reef experiences the seasonal oceanic influences of Indian Ocean and of the Indonesian-Through-Flow. The model for its development is derived from the post glacial (past 11,000 years) relative sea level curve, C14 dated facies changes and the reef growth phases extrapolated from the One Tree Reef model (Marshall & Davis 1982). A thorough visual examination of the reef was augmented with a series of 12 vibro-cores through algal-foraminiferal sand and coral, across the bioturbated platform. Changes in the lagoonal sediment facies were carbon dated giving dates ranging from 970 to 2020 (~70 years) BP. They indicated a major bio-facies change from robust vertical coral columns to an algal dominated reef crest and reef flats as sea level stabilised at ~2000 BP. Ashhmore Reef is presently characterised by high biodiversity and extensive coral growth, broad reef flats littered with coral boulders, and three vegetated cays. An extensive series of highly mobile and heavily bioturbated biogenic sand sheets adjoin two lagoons. Both are within a pronounced ovoid, algal-cemented, reef rim. The sediments comprised principally of Halimeda sp., coral fragments, foraminifera, molluscs and a range of coralline algae that infill the lagoon at up to 0.73 cm/yr. The three vegetated cays are capped with guano and all have wash-over deposits of pumice, wood, shell and coral.

The production of icebergs from Antarctic ice shelves represents fluctuations in the mass of the icesheet. Mapping the age, distribution and size of iceberg scour marks on the seafloor provides insight into the dynamics of the icesheet and circulation patterns through time. Sidescan sonar records from the Prydz Bay continental shelf are used to determine the relative ages of scour marks on this shelf as modern, relict and very relict, and their width, length and orientation. Modern scour marks on this shelf are shown to occur at average depths of 285 m, up to a maximum of 400 m. This range is broadly consistent with modern keel depths (248-352 m) for icebergs produced from the Amery Ice Shelf. Relict scours occur at average depths of 486 ± 78 m, while very relict scours occur at average depths of 650 ± 60 m. No iceberg scours are observed at depths greater than 750 m. The depth range of relict scours is consistent with iceberg scouring during periods of lower glacial sea level, combined with the production of icebergs with larger keel depths during major deglaciations. The very deep setting of the oldest scours implies the production of icebergs from a very thick iceshelf, possibly relating to major retreat of the icesheet towards the grounding line during periods of extreme glacial retreat.

<div>This data product contains geospatial seabed morphology and geomorphology information for Flinders Reefs and Cairns Seamount (Coral Sea Marine Park). These maps are intended for use by marine park managers, regulators, the general public and other stakeholders. A nationally consistent two-part (two-step) seabed geomorphology classification system was used to map and classify the distribution of key seabed features. </div><div><br></div><div>In step 1, semi-automated GIS mapping tools (GA-SaMMT; Huang et al., 2022; eCat Record 146832) were applied to a bathymetry digital elevation model (DEM) in a GIS environment (ESRI ArcGIS Pro) to map polygon extents (topographic high, low, and planar) and to quantitatively characterise their geometries. Their geometric attributes were then used to classify each shape into discrete Morphology Feature types (Part 1: Dove et al., 2020; eCat Record 144305). In step 2, the seabed geomorphology was interpreted by applying additional datasets and domain knowledge to inform their geomorphic characterisation (Part 2: Nanson et al., 2023; eCat Record 147818). Where available, backscatter intensity, seabed imagery, seabed sediment samples and sub-bottom profiles supplemented the bathymetry DEM and morphology classifications to inform the geomorphic interpretations.</div><div><br></div><div>The Flinders Reefs seabed morphology and geomorphology maps were derived from an 8 m horizontal resolution bathymetry DEM compiled from multibeam surveys (FK200429/GA4861: Beaman et al., 2020; FK200802/GA0365: Brooke et al, 2020), Laser Airborne Depth Sounder (LADS), Light Detection and Ranging (LiDAR) and bathymetry supplied by the Australian Hydrographic Office.</div><div><br></div><div>A subset of the FK200802/GA0365 multibeam survey was gridded at 1 m horizontal resolution to derive the key morphology and geomorphology features at the top of Cairns Seamount (-35 to -66 m; within the upper mesophotic zone).</div><div><br></div><div>The data product and application schema are fully described in the accompanying Data Product Specification. </div><div><br></div><div><em>Beaman, R., Duncan, P., Smith, D., Rais, K., Siwabessy, P.J.W., Spinoccia, M. 2020. Visioning the Coral Sea Marine Park bathymetry survey (FK200429/GA4861). Geoscience Australia, Canberra. <a href=https://dx.doi.org/10.26186/140048>https://dx.doi.org/10.26186/140048</a>; GA eCat record 140048</em></div><div><br></div><div><em>Brooke, B., Nichol, S., Beaman, R. 2020. Seamounts, Canyons and Reefs of the Coral Sea bathymetry survey (FK200802/GA0365). Geoscience Australia, Canberra. <a href=https://dx.doi.org/10.26186/144385>https://dx.doi.org/10.26186/144385</a>; GA eCat record 144385</em></div><div><br></div><div><em>Dove, D., Nanson, R., Bjarnadóttir, L. R., Guinan, J., Gafeira, J., Post, A., Dolan, Margaret F.J., Stewart, H., Arosio, R., Scott, G. (2020). A two-part seabed geomorphology classification scheme (v.2); Part 1: morphology features glossary. Zenodo. <a href=https://doi.org/10.5281/zenodo.4075248>https://doi.org/10.5281/zenodo.4075248</a>; GA eCat Record 144305 </em></div><div><br></div><div><em>Huang, Z., Nanson, R. and Nichol, S. (2022). Geoscience Australia's Semi-automated Morphological Mapping Tools (GA-SaMMT) for Seabed Characterisation. Geoscience Australia, Canberra. <a href=https://dx.doi.org/10.26186/146832>https://dx.doi.org/10.26186/146832</a>; GA eCat Record 146832</em></div><div><br></div><div><em>Nanson, R., Arosio, R., Gafeira, J., McNeil, M., Dove, D., Bjarnadóttir, L., Dolan, M., Guinan, J., Post, A., Webb, J., Nichol, S. (2023). A two-part seabed geomorphology classification scheme; Part 2: Geomorphology classification framework and glossary (Version 1.0) (1.0). Zenodo. <a href=https://doi.org/10.5281/zenodo.7804019>https://doi.org/10.5281/zenodo.7804019</a>; GA eCat Record 147818 </em></div>

<div>This data product contains geospatial seabed morphology and geomorphology information for the Beagle Marine Park and is intended for use by marine park managers, regulators, the general public and other stakeholders. A nationally consistent two-part (two-step) seabed geomorphology classification system was used to map and classify the distribution of key seabed features. </div><div><br></div><div>In step 1, semi-automated GIS mapping tools (GA-SaMMT; Huang et al., 2022; eCat Record 146832) were applied to bathymetry digital elevation models (DEM) in a GIS environment (ESRI ArcGIS Pro) to map polygon extents (topographic high, low, and planar) and quantitatively characterise their geometries. The geometric attributes were then used to classify each shape into discrete Morphology Feature types (Part 1: Dove et al., 2020; eCat Record 144305). In step 2, the seabed geomorphology was interpreted by applying additional datasets and domain knowledge to inform their geomorphic characterisation (Part 2: Nanson et al., 2023; eCat Record 147818). Where available, backscatter intensity, seabed imagery, seabed sediment samples and sub-bottom profiles supplemented the bathymetry DEM and morphology classifications to inform the geomorphic interpretations.</div><div><br></div><div>The Beagle Marine Park seabed morphology and geomorphology features were informed by a post survey report (Barrett et al., 2021). Seabed units were classified at multiple resolutions that were informed by the underlying bathymetry: </div><div><br></div><div>· A broad scale layer represents features that were derived from a 30 m horizontal resolution compilation DEM (Beaman et al 2022; eCat Record 147043). </div><div>· A series of medium and fine scale feature layers were derived from individual 1 m horizontal resolution DEMs (Nichol et al., 2019; eCat Record 130301). </div><div><br></div><div>The data product and application schema are fully described in the accompanying Data Product Specification. </div><div><br></div><div><em>Barrett, N, Monk, J., Nichol, S., Falster, G., Carroll, A., Siwabessy, J., Deane, A., Nanson, R., Picard, K., Dando, N., Hulls, J., and Evans, H. (2021). Beagle Marine Park Post Survey Report: South-east Marine Parks Network. Report to the National Environmental Science Program, Marine Biodiversity Hub. University of Tasmania.</em></div><div><br></div><div><em>Beaman, R.J. (2022). High-resolution depth model for the Bass Strait -30 m. <a href=https://dx.doi.org/10.26186/147043>https://dx.doi.org/10.26186/147043</a>, GA eCat Record 147043.&nbsp;</em></div><div><br></div><div><em>Dove, D., Nanson, R., Bjarnadóttir, L. R., Guinan, J., Gafeira, J., Post, A., Dolan, Margaret F.J., Stewart, H., Arosio, R., Scott, G. (2020). A two-part seabed geomorphology classification scheme (v.2); Part 1: morphology features glossary. Zenodo. <a href=https://doi.org/10.5281/zenodo.40752483>https://doi.org/10.5281/zenodo.4075248</a>; GA eCat Record 144305&nbsp;</em></div><div><br></div><div><em>Huang, Z., Nanson, R. and Nichol, S. (2022). Geoscience Australia's Semi-automated Morphological Mapping Tools (GA-SaMMT) for Seabed Characterisation. Geoscience Australia, Canberra. <a href=https://dx.doi.org/10.26186/146832>https://dx.doi.org/10.26186/146832</a>; GA eCat Record 146832 </em></div><div><em>&nbsp;</em></div><div><em>Nanson, R., Arosio, R., Gafeira, J., McNeil, M., Dove, D., Bjarnadóttir, L., Dolan, M., Guinan, J., Post, A., Webb, J., Nichol, S. (2023). A two-part seabed geomorphology classification scheme; Part 2: Geomorphology classification framework and glossary (Version 1.0) (1.0). Zenodo.<a href=https://doi.org/10.5281/zenodo.7804019>https://doi.org/10.5281/zenodo.7804019</a>; GA eCat Record 147818&nbsp;</em></div>