Total contribution of six recently discovered submerged coral reefs in northern Australia to Holocene neritic CaCO3, CO2, and C is assessed to address a gap in global budgets. CaCO3 production for the reef framework and inter-reefal deposits is 0.26-0.28 Mt which yields 2.36-2.72 x105 mol yr-1 over the mid- to late-Holocene (<10.5 kyr BP); the period in which the reefs have been active. Holocene CO2 and C production is 0.14-0.16 Mt and 0.06-0.07 Mt, yielding 3.23-3.71 and 5.32-6.12 x105 mol yr-1, respectively. Coral and coralline algae are the dominant sources of Holocene CaCO3 although foraminifers and molluscs are the dominant constituents of inter-reefal deposits. The total amount of Holocene neritic CaCO3 produced by the six submerged coral reefs is several orders of magnitude smaller than that calculated using accepted CaCO3 production values because of very low production, a 'give-up' growth history, and presumed significant dissolution and exports. Total global contribution of submerged reefs to Holocene neritic CaCO3 is estimated to be 0.26-0.62 Gt or 2.55-6.17 x108 mol yr-1, which yields 0.15-0.37 Gt CO2 (3.48-8.42 x108 mol yr-1) and 0.07-0.17 Gt C (5.74-13.99 x108 mol yr-1). Contributions from submerged coral reefs in Australia are estimated to be 0.05 Gt CaCO3 (0.48 x108 mol yr-1), 0.03 Gt CO2 (0.65 x108 mol yr-1), and 0.01 Gt C (1.08 x108 mol yr-1) for an emergent reef area of 47.9 x103 km2. The dilemma remains that the global area and CaCO3 mass of submerged coral reefs are currently unknown. It is inevitable that many more submerged coral reefs will be found. Our findings imply that submerged coral reefs are a small but fundamental source of Holocene neritic CaCO3, CO2, and C that is poorly-quantified for global budgets.

The contemporary crustal stress regime in south-eastern Australia can be traced back to the terminal Miocene. Increased coupling of the Australian and Pacific Plate boundary at this time resulted in regional-scale tilting, local uplift and erosion, and in the formation of unconformities in southern Australian basins. In the onshore Gippsland Basin the unconformity surface is overlain by an extensive sheet of fluvial sediment known as the Haunted Hill Formation (HHF). Open folds and flexures developed within the HHF over blind reverse and reverse oblique faults provide a record of deformation spanning much of the neotectonic period. The predominance of flexures and folds rather than discrete faulting at the surface complicates the assessment of slip rates over the last few seismic cycles. However, ages from an undeformed fill terrace bordering the Morwell River and crossing the Morwell Monocline suggest that it has been a minimum of 70 ka since the last deformation event on at least this structure. Stream profiles crossing the Snake Ridge, Yallourn and Rosedale Monoclines similarly reveal no evidence for recent tectonic displacement. Cosmogenic radionuclide (10Be and 26Al) burial ages of siliceous sediments sampled from tectonically uplifted HHF on the Yallourn, Morwell and Snake Ridge Monoclines provide constraint on the long-term evolution of these structures. Combined with stratigraphic and tectonic records from the offshore Gippsland Basin, these data provide a basis for informed seismic hazard assessment.

Abstract for the 18th NSW Coastal Conference

Dense coral-sponge communities on the upper continental slope (570 - 950 m) off George V Land, east Antarctica have been identified as Vulnerable Marine Ecosystems. We propose three main factors governing their distribution on this margin: 1) their depth in relation to iceberg scouring; 2) the flow of organic-rich bottom waters; and 3) their location at the head of shelf cutting canyons. Icebergs scour to 500 m in this region and the lack of such disturbance is a likely factor allowing the growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons which receive descending plumes of Antarctic Bottom Water formed on the George V shelf, which could entrain abundant food for the benthos. The canyons harbouring rich benthos are also those that cut the shelf break. Such canyons are known sites of high productivity in other areas due to strong current flow and increased mixing with shelf waters, and the abrupt, complex topography.

Geomorphic landscape features and associated surface materials are fundamental to groundwater recharge processes as they form the first layer through which surface water passes before it becomes groundwater. Different surface materials exhibit different water-holding capacity and hence permeability characteristics. In the Broken Hill Managed Aquifer Recharge project, surface-materials mapping in conjunction with geomorphic mapping, has assisted hydrogeological investigations, including recharge predictions, salinity hazard and the identification of potential infiltration basins. Prior to landform identification, LiDAR DEM data was levelled using trend surfaces to eliminate regional slope (~20m). As a consequence of this, an ArcGIS interactive contour tool could be used to identify specific breaks in elevation associated with landform features. Multivariate image analysis of elevation, high resolution SPOT and Landsat-derived wetness further enhanced the contrast between geomorphic elements to confirm mapping boundaries. While specific landforms can be characterised by particular surface materials, these sediments can vary within a single geomorphic feature. Consequently, SPOT multispectral satellite imagery was used to identify surface materials using principal component analysis and unsupervised classification. This approach generated 20 classes; each assigned a preliminary cover/landform attribute using SPOT imagery. Field data (surface and borehole sample, and observations at shallow pits) were used to refine the classification approach. Interactive mapping using a de-trended DEM provided a rapid, effective and accurate alternative to time consuming manual landform digitisation. The combination of these two new products - surface-materials and geomorphic maps - has assisted in the identification of potential recharge sites and naturally occurring infiltration sites.

The Ord is one of the largest rivers in northern Australia and is located in the Kimberley region of Western Australia. In this study we show that the lower Ord landscape near Kununurra in Western Australia consists of a large scale ancient landscape, possibly pre-Cambrian, being exhumed from beneath flat-lying Cambrian to Carboniferous cover rocks. Additional post-Permian landscapes are being formed by this process. The Ord Valley alluvium is of late Pleistocene to Holocene in age and consts off upward fining gravels, sands and clays infilling an inset valley profile. The Ord River initially flowed to the sea via the keep River estuary, however a major avulsion, possibly due to sedimentatain topping a low point in the surrounding valley walls, occurred possibly as recently as 1,800 years ago. As a result to mouth of the Ord shifted some 100 km to the east, to Cambridge Gulf, its course through the former alluvial plain and along the new course across the coastal plain was incised, and a scabland formed across the low point of Tararar Bar. This association of very ancient (pre-Paleozoic) landscape elements and by thin, very young weathering profiles and young sedimentary accumulations in alluvial valleys is paradoxical in the broader Australian pattern where very ancient landscape elements are associated with ancient sedimentary infill and weathering profiles.

The Queen Charlotte Fault (QCF) off western Canada is the northern equivalent to the San Andreas Pacific - America boundary. Geomorphology and surface processes associated with the QCF system have been revealed in unprecedented detail by recent seabed mapping surveys. The QCF bisects the continental shelf of British Columbia forming a fault-valley that is visible in multibeam sonar bathymetry data. The occurrence of the fault within a valley, and its association with what appear to be graben structures, suggest the fault may exhibit minor rifting (extension) as well as strike-slip motions in the region offshore from Haida Gwaii (Queen Charlotte Islands). Fault-valley formation, slumping and stranding of submarine canyon thalwegs are geomorphic expressions of QCF tectonism, illustrating the general applications of multibeam technology to marine geophysical research.

The legacy of multiple marine transgressions is preserved in a complex morphology of ridges, mounds and reefs on the Carnarvon continental shelf, Western Australia. High-resolution multibeam sonar mapping, underwater photography and sampling across a 280 km2 area seaward of the Ningaloo Coast World Heritage Area shows that these raised features provide hardground habitat for modern coral and sponge communities. Prominent among these features is a 20 m high and 15 km long shore-parallel ridge at 60 m water depth. This ridge preserves the largely unaltered form of a fringing reef and is interpreted as the predecessor to modern Ningaloo Reef. Landward of the drowned reef, the inner shelf is covered by hundreds of mounds (bommies) up to 5 m high and linear ridges up to 1.5 km long and 16 m high. The ridges are uniformly oriented to the north-northeast and several converge at their landward limit. On the basis of their shape and alignment, these ridges are interpreted as relict long-walled parabolic dunes. Their preservation is attributed to cementation of calcareous sands to form aeolianite, prior to the post-glacial marine transgression. Some dune ridges abut areas of reef that rise to sea level and are highly irregular in outline but maintain a broad shore-parallel trend. These are tentatively interpreted as Last Interglacial in age. The mid-shelf and outer shelf are mostly sediment covered with relatively low densities of epibenthic biota and have patches of low-profile ridges that may also be relict reef shorelines. An evolutionary model for the Carnarvon shelf is proposed that relates the formation of drowned fringing reefs and aeolian dunes to Late Quaternary eustatic sea level.

A number of terms used in this book are derived from the fields of biogeography and benthic ecology and these are defined in the glossary; the reader is also referred to the works cited at the end of this chapter for further information. Many of the case studies presented in this book refer to habitat classification schemes that have been developed based on principles of biogeography and ecology. For these reasons a brief overview is provided here to explain the concepts of biodiversity, biogeography and benthic ecology that are most relevant to habitat mapping and classification. Of particular relevance is that these concepts underpin classification schemes employed by GeoHab scientists in mapping habitats and other bioregions. A selection of published schemes, from both deep and shallow water environments, are reviewed and their similarities and differences are examined.

The overarching theme of this book (and for the GeoHab organisation in general) is that mapping seafloor geomorphic features is useful for understanding benthic habitats. Many of the case studies in this volume demonstrate that geomorphic feature type is a powerful surrogate for associated benthic communities. Here we provide a brief overview of the major geomorphic features that are described in the detailed case studies (which follow in Part II of this book). Starting from the coast we will consider sandy temperate coasts, rocky temperate coasts, estuaries and fjords, barrier islands and glaciated coasts. Moving offshore onto the continental shelf we will consider sandbanks, sandwaves, rocky ridges, shallow banks, coral reefs, shelf valleys and other shelf habitats. Finally, on the continental slope and deep ocean environments we will review the general geomorphology and associated habitats of escarpments, submarine canyons, seamounts, plateaus and deep sea vent communities.