geomorphology
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A range of physical descriptors of the seabed can potentially be used as surrogates for defining patterns of benthic marine biodiversity, including bathymetry, geomorphology and sediment type. These variables can be mapped, described and sampled across spatial scales that are of value to the management of the marine estate by providing a template for monitoring benthic ecosystems. As part of a four-year program (2007-2010) funded by the Australian Government, Geoscience Australia led marine surveys designed to collect robust datasets for the analysis of surrogacy relationships between a suite of physical variables and benthic biota in select areas of the Australian continental shelf. This paper focuses on results of the 2008 Carnarvon shelf survey, located within a Commonwealth Marine Park and adjacent to the World Heritage-listed Ningaloo Reef (Western Australia). High resolution multibeam sonar mapping, underwater video and benthic sampling revealed a complex geomorphology of ridges, mounds and sandy bedforms. The largest ridge extends 15 km alongshore is 20 m high and interpreted as a drowned forereef. Smaller ridges are ~1 km long, oriented northeast and preserve the form of aeolian dunes. Mounds are up to 5 m high and form extensive fields surrounded by flat sandy seabed. These ridges and mounds provide hardground habitat for diverse coral and sponge communities, whereas the surrounding sandy seafloor is characterised by few sessile benthic organisms. Multivariate analysis of these relationships is used to develop predictive models of benthic habitats, demonstrating the utility of high resolution physical data for informing management of these ecosystems.
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Deep sea environments occupy much of the sea floor, yet little is known about diversity patterns of biological assemblages from these environments. Physical mapping technologies and their availability are increasing rapidly. Sampling deep-sea biota over vast areas of the deep sea, however, is time consuming, difficult, and costly. Consequently, the growing need to manage and conserve marine resources, particularly deep sea areas that are sensitive to anthropogenic disturbance and change, is leading the promotion of physical data as surrogates to predict biological assemblages. However, few studies have directly examined the predictive ability of these surrogates. The physical environment and biological assemblages were surveyed for two adjacent areas - the western flank of Lord Howe Rise (LHR) and the Gifford Guyot - spanning combined water depths of 250 to 2,200 m depth on the northern part of the LHR, in the southern Pacific Ocean. Multibeam acoustic surveys were used to generate large-scale geomorphic classification maps that were superimposed over the study area. Forty two towed-video stations were deployed across the area capturing 32 hours of seabed video, 6,229 still photographs, that generated 3,413 seabed characterisations of physical and biological variables. In addition, sediment and biological samples were collected from 36 stations across the area. The northern Lord Howe Rise was characterised by diverse but sparsely distributed faunas for both the vast soft-sediment environments as well as the discrete rock outcrops. Substratum type and depth were the main variables correlated with benthic assemblage composition. Soft-sediments were characterised by low to moderate levels of bioturbation, while rocky outcrops supported diverse but sparse assemblages of suspension feeding invertebrates, such as cold water corals and sponges which in turn supported epifauna, dominated by ophiuroids and crinoids. While deep environments of the LHR flank .
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The Australian exclusive economic zone (EEZ) contains1.6 million km2 of submarine plateaus, equal to about 13.8% of the world's known inventory of these features. This disproportionate occurrence of plateaus presents Australia with an increased global responsibility to understand and protect the benthic habitats and associated ecosystems. This special volume presents the results of two major marine surveys carried out on the Lord Howe Rise plateau during 2003 and 2007, during which benthic biological and geological samples, underwater photographs, video and multibean sonar bathymetry data were collected. The benthic habitats present on Lord Howe Rise include hard/rocky substrates covering a small area of volcanic peaks (around 31 km2) and parts of other larger seamounts (eg. the Lord Howe Island seamount) which support rich and abundant epifaunal assemblages dominated by suspension feeding invertebrates. These habitats appear to qualify as ecologically and biologically significant areas under the United Nations Convention on Biological Diversity (CBD) scientific selection criterion 1 (uniqueness or rarity), 4 (vulnerability, fragility, sensitivity or slow recovery) and 7 (naturalness). The collection of papers included in this special volume represents a major advance in knowledge about benthic habitats of the Lord Howe Rise, but also about the ecology of plateaus in general.
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Remotely sensed imagery has been used extensively in geomorphology since the availability of early Landsat data. Since that time, there has been a steady increase in the range of sensors offering data with increased spatial and spectral resolutions, from both government and commercial satellites. This has been augmented with an increase in the amount and range of airborne surveys carried out. Since 2000, digital elevation models have become widely available through the application of interferometric synthetic aperture radar, photogrammetry and laser altimetry (specifically LiDAR) with extensive uptake by geomorphologists. In addition, hyperspectral imaging, radiometrics and electromagentics have been made more accessible, whilst there has been increased use of close-range (<200 m) imaging techniques for very high resolution imaging. This paper reviews the primary sources for DEMs from satellite and airborne platforms, as well as briefly reviewing more traditional multi-spectral scanners, and radiometric and electromagnetic systems. Examples of the applications of these techniques are summarised and presented within the context of landscape pattern recognition and modelling. Finally, the wider issues of access to geographic information and data distribution are discussed.
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Lord Howe Island in the southwest Pacific Ocean is the subaerial remnant of a Late Miocene hot-spot volcano. Erosion of the island has formed a shallow (20 - 120 m) sub-tropical carbonate shelf 24 km wide and 36 km long. On the mid shelf an extensive relict coral reef (165 km2) surrounds the island in water depths of 30-40 m. The relict reef comprises sand sheet, macroalgae and hardground habitats. Inboard of the relict reef a sandy basin (mean water depth 45 m) has thick sand deposits. Outboard of the relict reef is a relatively flat outer shelf (mean depth 60 m) with bedrock exposures and sandy habitat. Infauna species abundance and richness were similar for sediment samples collected on the outer shelf and relict reef features, while samples from the sandy basin had significantly lower infauna abundance and richness. The irregular shelf morphology appears to determine the distribution and character of sandy substrates and local oceanographic conditions, which in turn influence the distribution of different types of infauna communities.
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Short contribution to "Atlas of Submarine Glacial Landforms"
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An examination of regionally extensive hill-shaded SRTM 90m resolution and DLI 10 m resolution digital elevation data and discussions with government and industry geologists familiar with the local geology has resulted in the identification of thirty eight previously unrecognised linear topographic scarps in the southwest and central west of Western Australia. I contend that most of these relate to Quaternary surface-rupturing earthquakes. If validated, this more than doubles the number of Quaternary fault scarps known from this area, bringing the total to sixty. The newly recognised scarps average between 25 km and 50 km in length and from ~1.5 m to 20 m in height. The geometric, recurrence and spatial attributes of these features makes it possible to propose a model describing the causative seismicity. The model contends that uniform contractional strain in the ductile lithosphere manifests as localised, transient and recurrent brittle deformation in zones of pre-existing crustal weakness in the upper lithosphere. The data presented allow for ready calculation of the maximum probable magnitude earthquake for the southwest of Western Australia, and identify 'earthquake prone' regions of interest to seismic hazard assessors.
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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.
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To be completed
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Australia wide mineralogical maps have recently been generated and released by CSIRO and Geoscience Australia using the 14 band satellite-borne ASTER imaging sensors. Seventeen map products related to surface composition have been produced for the geoscience community. Band parameters were developed based on spectral absorption features representing either abundance of mineral groups, specific minerals and their chemistry, vegetation cover or regolith related characteristics. A detailed study was undertaken, investigating the geoscience exploration capabilities of these newly released map products, individually, and integrated with airborne geophysics and digital elevation models over the Mt Fitton test site in northern Flinders Ranges, South Australia. This site includes the Mt Fitton talc deposits, gold prospects, and areas of hydrothermal activity and metasomatism.