Northeast Australia Research Articles

The Growth in Low-Cost Carrier Services in Queensland: Implications for Regional Tourism Destinations

After an aborted start in the early 1990s, the Australian domestic aviation market has seen a significant shift from a duopoly market in which two full-service airlines competed with similar services, to the emergence of three airlines/four brands—three of which are low cost carriers. Aggressive marketing strategies, low fares and increased capacity by low cost carriers Virgin Blue, Jetstar and Tiger Airways have benefited many regional destinations. The research presented in this paper shows that as air fares have fallen consumers have switched from private cars, long distance coach and rail to air. The reasons for this switch include consumer recognition of the savings that are possible through lower travel costs by air and that more time may be spent at the destination. The impact of switching modes is demonstrated by analysing the impact of LCCs on Cairns, a major coastal destination in northeast of Australia.

地域連携によるオーストラリア北東部の熱帯雨林の復元活動の特徴と課題

The purpose of this study was to investigate the characteristics and problems of restoration activities and in the rainforest of the Atherton Tableland, Northeast Australia, from the viewpoint of regional alliances. Using research literature and field surveys, 12 organizations involved in restoration activities in the rainforest area were investigated. This study showed that government, research and education organizations, and environmental NPOs carried out restoration activities through alliances, in which different sectors cooperated in a mutually complementary relationship. The issues included 1) obtaining grants from a broad range of organizations to restore the rainforest, 2) the necessity of strategy involving local citizens to the restoration activities by activating public information and educational programs.

Flow separation and vertical motions in a tidal flow interacting with a shallow-water island

This paper reports on the case study of Rattray Island (Great Barrier Reef, northeast Australia), lying perpendicular to tidal flow in shallow waters. At ebb and flood, attached (stable) eddies develop in the wake where swirls of turbidity suggest that sediment-laden waters are brought to the surface as a result of vertical transport. Both eddy and tip upwellings are encountered in the tidal flow around Rattray Island but there is currently no clear-cut answer as to which secondary flow generates upwelling with the largest intensity. This paper addresses this specific issue through idealized and realistic high-resolution numerical experiments. The analysis is supported by physical arguments based on the theory of flow separation. Given Rattray's geometry and surrounding bathymetry, the mechanism of flow separation in shallow waters helps explain the asymmetry in size of the eddies and their intensity. The results of idealized numerical experiments also suggest that eddy and tip upwellings may be of similar intensity at Rattray Island.

Phylogeography of the parasitic fly Batrachomyia in the Wet Tropics of north-east Australia, and susceptibility of host frog lineages in a mosaic contact zone

Parasites could differentially impact intraspecific host lineages due to genetic, phenotypic, ecological, or behavioural differences between the lineages, or the development of reproductive isolation between them. Batrachomyia (Diptera: Chloropidae) are flies that exclusively parasitize Australian frogs, and in the Wet Tropics rainforest of north-east Australia larvae are largely restricted to the green-eyed tree frog Litoria genimaculata (Anura: Hylidae). This frog species consists of two highly divergent genetic lineages that overlap in two nearby, but independent, contact zones. At one contact zone there has been extensive phenotypic divergence and speciation between the lineages whereas, at the other contact relatively lower levels of phenotypic divergence and reproductive isolation suggest that speciation has not occurred. In the present study we tested: (1) whether the deep phylogeographic divergence between northern and southern host populations is mirrored by congruent genetic structuring in the parasite populations and (2) whether the host lineages are differentially impacted by parasitism. We found that the two divergent frog lineages are parasitized by a single lineage of Batrachomyia, which exhibits strikingly little phylogeographic structuring. We found a significant difference in Batrachomyia prevalence between the host lineages at mixed lineage sites in both contact zones, with the magnitude and direction of this effect being consistent in both. The pattern did not differ between the two contacts even though recent phenotypic divergence and speciation has occurred between the lineages at one contact but not the other. Taken together, this suggests a fundamental difference in susceptibility between the genetically divergent host lineages. Using weight relative to body length as a measure of body condition, we found no differential impact of parasitism on the body condition of each host lineage, and no evidence that parasitism impacts the body condition of the host in general.

Description of a new species of catshark, Atelomycterus marnkalha n. sp. (Carcharhiniformes: Scyliorhinidae) from north-east Australia

A new atelomycterine catshark species (Scyliorhinidae: Atelomycterinae), Atelomycterus marnkalha n. sp., is described from north-east Australia (Great Barrier Reef Marine Park, Torres Strait and Gulf of Carpentaria). It differs from A. baliensis, A. marmoratus and A. macleayi in having posteroventally sloping dorsal fins, a lower precaudal vertebrae count and smaller adult size. Most similar to the Western Australian catshark species A. fasciatus, A. marnkalha differs from this species in having a larger anal fin, lateral denticles with prominent shallow depressions, claspers of adult males with a cover rhipidion lacking an obvious notch and its colour pattern with prominent white spots and fewer, smaller black spots.

Patch Configuration Non-linearly Affects Sediment Loss across Scales in a Grazed Catchment in North-east Australia

A principle of the cross-scale interaction (CSI) framework is that disturbance-induced landscape changes resulting in coarser-grained spatial structure may non-linearly amplify transfer processes across scales. We studied suspended sediment losses at two spatial scales (0.24 m2 plots and ca. 0.25 ha hillslopes of about 140 m in length) in a semiarid savanna landscape to determine whether the spatial structure of grassy and bare soil areas introduced a non-linear amplification of sediment loss. Sediment loss rates from 0.24 m2 bare plots averaged 1.527 t ha−1 y−1, which was 23 times the loss rate from nearby grassy plots (0.066 t ha−1 y−1). These rates were then extrapolated linearly to two hillslopes separated by only 200 m and having similar total grass cover, slope and soil type but differing in the spatial structure of bare soil patches. The coarse-grained hillslope had a large bare patch on its lower slope, whereas the fine-grained hillslope had no bare soil patches when quantified at a 4 m grid-cell resolution. Measured sediment loss from the fine-grained hillslope averaged 0.050 t ha−1 y−1, whereas the average sediment loss from the coarse-grained hillslope was 2.133 t ha−1 y−1. By linearly extrapolating from the plot scale, the expected sediment loss for the fine-grained hillslope was 0.066 t ha−1 y−1, which is similar to that observed. The expected sediment loss for the coarse-grained hillslope was 0.855 t ha−1 y−1, where linear extrapolation assumed a 46:54 ratio of bare to grassy plots and that the spatial arrangement of plots does not affect sediment loss processes. For the coarse-grained hillslope observed sediment loss is 2.5 times greater than that expected by linear extrapolation from the plot scale. This result indicates a cross-scale interaction related to spatial configuration of patches. We suggest that there were non-linearities in hillslope ecohydrological transfer processes (runoff, erosion) across scales due to a specific patch configuration that greatly amplified sediment loss because the pattern failed to slow runoff and retain sediment before it entered a creek. This example supports the CSI framework and indicates the importance of considering the effect of spatial structure when predicting system dynamics at different scales.

Effect of spatial variation on salinity tolerance of macroinvertebrates in Eastern Australia and implications for ecosystem protection trigger values

Salinisation of freshwater has been identified as a serious environmental issue in Australia and around the world. Protective concentrations (trigger values) for salinity can be used to manage salinity impacts, though require locally relevant salinity tolerance information. 72-h acute salinity tolerance values were determined for 102 macroinvertebrates collected from 11 locations in four biologically distinct freshwater bio-regions in Northeast Australia and compared with sensitivities observed in Southeast Australia. The salinity tolerance of individual taxa was consistent across Northeast Australia and between Northeast and Southeast Australia. However, two distinct communities were identified in Northeast Australia using distributions of the acute tolerance values and a calculated index of salinity sensitivity. Salinity trigger values should therefore be representative of local or regionally relevant communities and may be adequately calculated using sensitivity values from throughout Eastern Australia. The results presented provide a basis for assessing salinity risk and determining trigger values for salinity in freshwater ecosystems at local and regional scales in Eastern Australia.

Population ecology of the southern cassowary Casuarius casuarius johnsonii, Mission Beach north Queensland

Little is known of the ecology and population dynamics of the world’s largest avian frugivore. This study investigated the population of endangered southern cassowary at Mission Beach, northeast Australia, and examined the problems associated with determining population size and density of this keystone species. Using the results of an intensive field survey aimed at estimating absolute numbers of individual cassowaries, the appropriate sampling methodology for rare and elusive species was explored. Approximately 102 km2 of rainforest was surveyed using 346 km of search transects. Of a total of 110 cassowaries, there were 49 adults (28 male, 19 female, 2 unknown), 28 subadults, 31 chicks, and 2 independent birds of unknown status. This is approximately 35% of the adult population previously estimated for the Mission Beach area. Overall adult cassowary density was 0.48 adults/km2; the density of independent birds, i.e. adults and subadults, was 0.78 birds/km2. Mean indicative home range (IHR) for adult females and males was 2.13 and 2.06 km2, respectively. Mean IHR of subadults was smaller at 0.95 km2. It was concluded that the previous practice of surveying small areas at Mission Beach (<4 km2) has led to consistent overestimation of cassowary population density, up to six times its real number. It is shown that a sample plot between 5 and 15 km2 is necessary to approximate true cassowary density. These findings have significant application to the conservation of cassowaries in New Guinea and in the Wet Tropics World Heritage Area of Australia.

Bathymetric expression of the Fitzroy River palaeochannel, northeast Australia: Response of a major river to sea-level change on a semi-rimmed, mixed siliciclastic-carbonate shelf

Palaeo-river channels record the response of alluvial and estuarine depositional environments to sea-level change, and are also important geological indicators of former subaerial unconformities. Earlier studies have characterised lowstand palaeochannels on the central Great Barrier Reef (GBR) shelf of northeastern Australia, reporting channel entrenchment, shelf aggradation, and topographic control of rivers by the outer shelf reef barrier. We report the bathymetric expression of a palaeochannel corresponding to the last glacial lowstand path of the Fitzroy River, a high sediment yield river in the southern GBR. During regression and lowstand, the Fitzroy River palaeochannel entrenched into the low-gradient middle shelf, and may have begun to incise the steeper outer shelf between the exposed reef platforms. The wide spacing of outer shelf reefs and the continuous seabed slope may have enabled the palaeo-Fitzroy to maintain connection with the lowstand shoreline without becoming trapped behind shelf edge reefs. The palaeochannel now forms a prominent depression across the middle and outer shelf. Evidently, the sloping inter-reefal seabed of the southern GBR, coupled with tidal processes and wave exposure, has limited shelf aggradation since the transgression. This finding provides evidence that modern bathymetry can reflect palaeochannel location on the GBR shelf. Our results offer new insights into the evolution of the southern GBR shelf, and show that no single existing model is able to adequately explain the behaviour of lowstand palaeochannels on rimmed siliciclastic/carbonate shelves.

Tropical river flow and rainfall reconstructions from coral luminescence: Great Barrier Reef, Australia

Rainfall and river flow in northeast Queensland, Australia, are highly seasonal and show high interannual and decadal variability that is modulated by El Niño–Southern Oscillation (ENSO) events and the Pacific Decadal Oscillation (PDO). Reconstructions of October–September freshwater input to the Great Barrier Reef lagoon and October–September Queensland rainfall are developed from visual assessment of the occurrence and intensity of luminescent lines in massive Porites from up to 25 coral cores from 15 nearshore reefs regularly influenced by river flood plumes. Separate reconstructions are developed for four rivers (Herbert, Burdekin, Pioneer, and Fitzroy), and these are used to reconstruct total annual freshwater flow into the Great Barrier Reef (69–74% variance calibrated) and an index of Queensland rainfall (53–57% variance calibrated). The reconstructions extend back to 1631 but are most reliable from 1661 and capture significant decadal variability. The reconstructions provide insights into long‐term tropical rainfall and river flow variability and the behavior of ENSO and the PDO over several centuries. Significant, though weak, relationships are found between these reconstructions and an independent reconstruction of ENSO. The reconstructions highlight that observations from the instrumental records of high interannual and decadal rainfall and river flow variability in northeast Australia also characterize the past few centuries. Although there appears to be no overall trend toward wetter or drier conditions, the reconstructions suggest that the variability of rainfall and river flow has increased during the twentieth century with more very wet and very dry extremes than in earlier centuries, as projected for the region as a consequence of global warming.

Whole core versus plugs: Scale dependence of porosity and permeability measurements in platform carbonates

This study compares laboratory measurements of porosity and permeability between twenty-three whole-core samples and fifty-four 1-in. (25-mm) plugs drilled from the centers of the same samples. All samples are coarsely bioclastic carbonates from Miocene carbonate platforms of the Marion Plateau, offshore northeast Australia (1 limestone and 22 dolostones). Whole-core porosities tend to be slightly higher (average 1.4 porosity units) than plug porosities, probably reflecting a lower surface/volume ratio for the larger samples. Permeability differences between whole cores and plugs vary greatly from sample to sample, but whole-core permeability tends to be higher in cases where larger differences are observed. This tendency may reflect flow through optimal-flow networks that occupy a small proportion of the total rock volume and are therefore not included within most plugs. Previous studies suggest that increasing permeability with sample scale may be a general characteristic of heterogeneous porous media. The present results provide a quantitative basis for evaluating the necessity and advantages of using whole cores as opposed to plugs for petrophysical characterization of carbonate reservoirs.

Provenance comparisons of Permian to Jurassic tectonostratigraphic terranes in New Zealand: perspectives from detrital zircon age patterns

U–Pb detrital zircon ages (LAM-ICPMS) are reported for 20 greywackes and sandstones from seven major tectono-stratigraphic terranes of the Eastern Province of New Zealand (Cretaceous to Carboniferous) to constrain sediment provenances. Samples are mainly from three time horizons: Late Permian, Late Triassic and Late Jurassic. Age datasets are analysed as percentages in geological intervals, and in histogram and cumulative probability diagrams. The latter discriminate significant zircon age components in terms of terrane, sample stratigraphic age, component age, precision and percentage (of total set). Zircon age distributions from all samples have persistent, large Triassic–Permian, and very few Devonian–Silurian, populations, features which exclude a sediment provenance from the early Palaeozoic, Lachlan Fold Belt of southeast Australia or continuations in New Zealand and Antarctica. In the accretionary terranes, significant Palaeozoic (and Precambrian) zircon age populations are present in Torlesse and Waipapa terranes, and variably in Caples terrane. In the fore-arc and back-arc terranes, a unimodal character persists in Murihiku and Brook Street terranes, while Dun Mountain–Maitai terrane is more variable, and with Caples terrane, displays a hybrid character. Required extensive Triassic–Permian zircon sources can only be found within the New England Fold Belt and Hodgkinson Province of northeast Australia, and southward continuations to Dampier Ridge, Lord Howe Rise and West Norfolk Ridge (Tasman Sea). Small but significant Palaeozoic (and Precambrian) age components in the accretionary terranes (plus Dun Mountain–Maitai terrane), have sources in hinterlands of the New England Fold Belt, in particular to mid-Palaeozoic granite complexes in NE Queensland, and Carboniferous granite complexes in NE New South Wales. Major and minor components place sources (1) for the older Torlesse (Rakaia) terrane, in NE Queensland, and (2) for Waipapa terrane, in NE New South Wales, with Dun Mountain–Maitai and Caples terrane sources more inshore and offshore, respectively. In Early Jurassic–Late Cretaceous, Torlesse (Pahau) and Waipapa terranes, there is less continental influence, and more isolated, offshore volcanic arc sources are suggested. There is local input of plutonic rock detritus into Pahau depocentres from the Median Batholith in New Zealand, or its northward continuation on Lord Howe Rise. Excepting Murihiku and Brook Street terranes, all others are suspect terranes, with depocentres close to the contemporary Gondwanaland margin in NE Australia, and subsequent margin-parallel, tectonic transport to their present New Zealand position. This is highlighted by a slight southeastward migration of terrane depocentres with time. Murihiku and Brook Street terrane sources are more remote from continental influences and represent isolated offshore volcanic depocentres, perhaps in their present New Zealand position.

Holocene sediments of Lake Barrine, north-east Australia, and their implications for the history of lake and catchment environments

Lake Barrine (17° 15′ S, 145° 38′ E, 721 m a.s.l.) lies in a maar crater surrounded by tropical rainforest. Its surface area is 1 km 2 and its maximum depth 67 m. It has no inflow streams and an outlet only active in the wet summer months. The sediments underlying the lake have been investigated by numerous Mackereth cores and in-situ frozen slabs. In addition to lithological descriptions, selected samples have been analysed for grain size, bulk density and combustible content, mineralogy and chemistry, palaeomagnetism, pollen and charcoal. A chronology was established from radiocarbon dating of 211 sediment samples. The deposits are divisible into three main strata. Between about 16 ka and 9.7 ka cal BP they are mainly inorganic representing occasional, very energetic, inwash from the lightly vegetated inner walls of the crater; only a few small enclaves were perennially flooded. Between 9.7 and 5.4 ka cal BP sediments were, for the most part, finely grained with a substantial organic component. Their indications are of a water level rising overall but not at a constant rate. From time to time erosion and redeposition of marginal materials and older sediments took place. By 7.3 ka BP, as rainforest began to cover the catchment, the water level had risen sufficiently for reducing conditions to be established in its deeps and subsequent deposits indicated pedogenesis beneath the forest and reduced runoff to the lake. Between 9.7 and 7.3 ka cal BP the catchment erosion rate was 859 kg (dry wt) ha − 1 ka − 1 but this fell to 267 kg ha − 1 ka − 1 from 7.3 to 5.4 ka cal BP. From 5.4 ka cal BP to the present, the sediments beneath > 55 m of the modern lake are strongly and finely laminated. This was the result of intermittent relocation of detritus from shallower to deeper water when the lake's thermal stability was reduced by unusually low winter temperatures, the resultant lamination being preserved under a persistent monimolimnion. Lamination counts indicate that this has happened more than a thousand times in the last 5.4 ka. By 3.2 ka cal BP the water level had reached the modern outlet and its oscillations thereby minimised. Between 5.4 ka cal BP and 3.2 ka cal BP, the catchment sediment yield was 112 kg ha − 1 ka − 1 , rising to 146 kg ha − 1 ka − 1 thereafter. In the period between 9.7 and 3.2 ka cal BP the lake volume increased from virtually nothing to almost 36 Gl.

Drought‐related tree death of savanna eucalypts: Species susceptibility, soil conditions and root architecture

AbstractQuestions: For eucalypt savanna in northeast Australia subject to multi‐year rainfall deficits this paper asks whether (1) dominant tree species (Ironbarks, Boxes) are more drought susceptible than the sub‐dominant Bloodwoods; (2) whether soil moisture is beyond wilting point in surface soil layers but available at depth; (3) soil conditions (moisture availability and texture) are related to tree death during drought; (4) the root systems of the Boxes and Ironbarks are shallower than the Bloodwoods; and the survivors of drought within species have deeper root systems than those that died.Location: Central Queensland, Australia.Methods: Patterns of tree death between eucalypt species were compared from field data collected after drought. Soil conditions during drought were described and compared with patterns of tree death for the Ironbark Eucalyptus melanophloia. The basal area and orientation of coarse roots were measured on upturned trees after broad‐scale tree clearing, and compared between species, and between live and dead trees with tree size as a covariate.Results: Drought‐induced tree death was higher for dominant Ironbark‐Box than for sub‐dominant Bloodwoods. During a moderate to severe drought in 2004, 41% of 100 cm deep subsoils had soil matric potential less than‐5600 kPa. The drought hardy Bloodwoods had a greater root basal area and particularly so for vertical roots compared to the drought sensitive Ironbark‐Box. Within species there was no significant difference in root basal area characteristics between trees that were recently killed by drought and those that remained relatively healthy. Surface soil moisture availability was lower where tree densities were high, and tree death increased as surface soil moisture became less available. Tree death was also greater as the clay content of sub‐soils increased.Discussion: The study suggests species with roots confined to upper soil layers will suffer severe water stress. The results strongly indicate that root architecture, and the way it facilitates water use during drought, is important for the relative dominance of the tree species. Patchiness in drought‐induced tree death seems to be at least partially a product of heterogeneity in sub‐soil conditions and competition for soil moisture.

Greater frequency variability of landfalling tropical cyclones at centennial compared to seasonal and decadal scales

Assessing risk from tropical cyclones and predicting the impact of this hazard under a human altered climate is based exclusively upon the behaviour of these events over the past 50–100 yr and often less. Critical to these determinations is an understanding of the full extent of the natural variability of this hazard. The coarse resolution of millennial scale sedimentary records, brevity of the instrumental register, imprecision of longer historical accounts and lack of any long-term, high resolution records has led to the assumption that the total variability of tropical cyclone behaviour is encompassed within the seasonal to multi-decadal oscillations observed to date. We present a near 800 yr long, annual resolution isotope record of tropical cyclones in northeast Australia which displays marked centennial scale regimes. Our record demonstrates that the frequency variability of intense landfalling cyclones is greatest at centennial scale compared to seasonal and decadal oscillations. Switching between centennial scale regimes in this record occurred rapidly (10–20 yr) highlighting the importance of accounting for this phenomenon in coastal planning and risk assessment. Our study highlights the importance of obtaining high resolution multi-century records of tropical cyclone activity in order to more accurately assess future impacts of this hazard to human society.

Modelling the risk of cyclone wave damage to coral reefs using GIS: a case study of the Great Barrier Reef, 1969–2003

Tropical cyclones (hurricanes and typhoons) produce high winds that can generate waves capable of damaging coral reefs. As cyclones frequently pass through northeast Australia's Great Barrier Reef (GBR), it is important to understand how the spatial distribution of reef damage changes over time. However, direct measurements of wave damage, or even wave heights or wind speeds, are rare within the GBR. An important factor in estimating whether cyclone damage was possible is the magnitude and duration of high‐energy wind and waves. Thus, before the spatio‐temporal dynamics of past cyclone damage can be modelled, it is necessary to reconstruct the spread, intensity, and duration of high‐energy conditions during individual cyclones. This was done every hour along the track taken by each of 85 cyclones that passed near the GBR from 1969 to 2003, by implementing a cyclone wind hindcasting model directly within a raster GIS using cyclone data available from the Australian Bureau of Meteorology. Three measures of cyclone energy (maximum wind speed—MAX, duration of gales—GALES, and continuous duration of gales—CGALES) were derived from these data. For three cyclones, where field data documenting actual reef damage from cyclone‐generated waves were available, the predictive ability of each measure was assessed statistically. All three performed better in predicting reef damage at sites surveyed along the high‐energy reef front than those surveyed along the more protected reef back. MAX performed best for cyclone Joy (r 2 = 0.5), while CGALES performed best for cyclones Ivor (r 2 = 0.23) and Justin (r 2 = 0.48). Using thresholds for MAX and GALES obtained via comparison with field data of damage, it was possible to produce a preliminary prediction of the risk of wave damage across the GBR from each of the 85 cyclones. The results suggest that while up to two‐thirds of the GBR was at risk from some damage for 30–50% of the time series (∼18 out of 35 years), only scattered areas of the region were at risk more frequently than that.

Importance of canopy connectivity for home range and movements of the rainforest arboreal ringtail possum (Hemibelideus lemuroides)

Roads and powerline corridors destroy canopy connectivity in the rainforest of north-east Australia. We tested the hypotheses that linear barriers affect (a) the alignment of home ranges, (b) use of habitat either side of linear barriers, and (c) the crossing of them by the strictly arboreal lemuroid ringtail possum (Hemibelideus lemuroides), which is known to be vulnerable to habitat fragmentation. Radio-tracking and a translocation experiment were conducted at a narrow 7-m-wide road and an 80-m-wide powerline. Homes ranges of lemuroid ringtails ranged from 0.15 to 1.67 ha (minimum convex polygon) and were aligned with the road but not powerline corridors. When lemuroid ringtails were experimentally translocated, wider canopy clearings over roads reduced their capacity to return to their original home range, and the powerline corridor was a nearly insurmountable barrier. No possums were observed crossing roads or the powerline corridor at ground level or residing in the intervening matrix, indicating that loss of canopy connectivity has a negative impact on their movements.

Drought-related tree death of savanna eucalypts: Species susceptibility, soil conditions and root architecture

Questions: For eucalypt savanna in northeast Australia subject to multi-year rainfall deficits this paper asks whether (1) dominant tree species (Ironbarks, Boxes) are more drought susceptible than the sub-dominant Bloodwoods; (2) whether soil moisture is beyond wilting point in surface soil layers but available at depth; (3) soil conditions (moisture availability and texture) are related to tree death during drought; (4) the root systems of the Boxes and Ironbarks are shallower than the Bloodwoods; and the survivors of drought within species have deeper root systems than those that died. Location: Central Queensland, Australia. Methods: Patterns of tree death between eucalypt species were compared from field data collected after drought. Soil conditions during drought were described and compared with patterns of tree death for the Ironbark Eucalyptus melanophloia. The basal area and orientation of coarse roots were measured on upturned trees after broad-scale tree clearing, and compared between species, and between live and dead trees with tree size as a covariate. Results: Drought-induced tree death was higher for dominant Ironbark-Box than for sub-dominant Bloodwoods. During a moderate to severe drought in 2004, 41% of 100 cm deep subsoils had soil matric potential less than-5600 kPa. The drought hardy Bloodwoods had a greater root basal area and particularly so for vertical roots compared to the drought sensitive Ironbark-Box. Within species there was no significant difference in root basal area characteristics between trees that were recently killed by drought and those that remained relatively healthy. Surface soil moisture availability was lower where tree densities were high, and tree death increased as surface soil moisture became less available. Tree death was also greater as the clay content of sub-soils increased. Discussion: The study suggests species with roots confined to upper soil layers will suffer severe water stress. The results strongly indicate that root architecture, and the way it facilitates water use during drought, is important for the relative dominance of the tree species. Patchiness in drought-induced tree death seems to be at least partially a product of heterogeneity in sub-soil conditions and competition for soil moisture.

Time-space evaluation of the tectono-metallogenic evolution of the northern Tasman Fold Belt System, northeast Queensland, Australia

The Tasman Fold Belt System in eastern Australia provides a record of the Palaeozoic geological history and growth of the Australian continent along the proto-Pacific margin of Gondwana inboard of an extensive and long-lived subduction system. The Hodgkinson and Broken River provinces represent prominent geological elements of this system and together form the northern Tasman Fold Belt System. Integration of newly-obtained data with a time-space evaluation of the geological evolution of the Hodgkinson and Broken River provinces, as well as other terranes in the northern Tasman Fold Belt System, allows for the development of a geodynamic model for the Palaeozoic evolution of the northern Tasman Fold Belt System. Our model indicates that three cycles of extension ? contraction occurred during the Palaeozoic evolution of the northern Tasman Fold Belt System. Episodes of extension were controlled by roll-back of the subduction system along the Australian margin, whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments (i.e., micro-continental blocks / oceanic plateaux) at the subducting trench. Our composite interpretative model on the geodynamic evolution of the northern Tasman Fold Belt System integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of Palaeozoic geodynamics along the margin of Gondwana in northeast Australia.

Geology of the submarine Kenn Plateau off northeast Australia: a rifted continental block

New seismic reflection data and dredged rock samples confirm that the submarine Kenn Plateau is a thinned continental fragment. It is twice the size of Tasmania and lies 400 km east of central Queensland beyond Cato Trough. East and northeast trending faults separate thinly sedimented basement highs from sedimentary basins with >2 km of Cretaceous and younger strata. In the Late Cretaceous the future plateau fitted against Australia south of Marion Plateau, and consisted of Late Triassic and younger basins unconformably overlying the New England Fold Belt. After Lower Cretaceous rift volcanism, the Kenn Plateau itself formed by Late Cretaceous extension and breakup. Paleocene drifting moved it northeast and rotated it 30° anticlockwise, leaving behind Tasman Basin oceanic basalts. Siliciclastic sediments poured into the basins from the Australian mainland and local highs. After a regional Paleocene-Eocene boundary unconformity, siliciclastic sedimentation resumed nearshore. In deep water, deposition of radiolarian chalks ended at the regional Eocene-Oligocene boundary unconformity, and pure biogenic carbonates accumulated in warming surface waters. From the Middle Eocene, calcarenite formed on the shelves of the subsiding plateau. Some seismic profiles show Middle to Late Eocene compression, probably related to New Caledonian obduction to the east. Hotspots formed parts of two volcanic chains as the plateau moved northward: in the west, Upper Eocene and younger volcanics of the Tasmantid chain; and in the east Upper Oligocene and younger volcanics of the Lord Howe chain. The subsiding volcanoes were fringed by reefs, some of which have persisted until now; others have subsided to form guyots. The plateau has subsided 2000 m or more since its breakup and is now subject solely to pelagic carbonate sedimentation.