Middle to early Late Ordovician hydrothermal veining in the Molong Volcanic Belt,northeastern Lachlan Fold Belt: Sedimentological evidence     

G. H. Packham  J. B. Keene  L. M. Barron 《Australian Journal of Earth Sciences》2013,60(2):257-269

Detrital volcanic and vein quartz, accompanied by felsic volcanic debris, occur as minor constituents in the Ordovician subduction‐related mafic volcanics of the Molong Volcanic Belt. In the western province of the Molong Volcanic Belt, detrital quartz is present in the three episodes of the mafic Volcanics. Volcanic quartz occurs in allochthonous limestone blocks in the Bendigonian Hensleigh Siltstone overlying the Mitchell Formation. The second volcanic episode (the Fairbridge Volcanics) commenced after a hiatus of approximately 20 million years and lasted around 10 million years from Darriwilian to Gisbornian time. Locally derived vein quartz, volcanic quartz and felsic detritus are concentrated at the bases of autochthonous Wahringa and Yuranigh Limestone Members of the volcanics and are extensive and abundant in basal beds of the regional Eastonian limestone body that transgressed over an eroded volcanic centre at Cargo. This early Eastonian debris, deposited early in an 8 million‐year volcanic hiatus preceding the final Ordovician Bolindian volcanism, establishes a pre‐Eastonian age for mineralisation at Cargo. It is inferred that the pauses in volcanism were preceded by magmatic fractionation, intrusion and hydrothermal activity and followed by erosion, subsidence and deposition of autochthonous limestones. Minor occurrences of vein and volcanic quartz are found in Bolindian volcanogenic sediments of the third volcanic phase. It is concluded that hydrothermal vein formation (and mineralisation by inference) was associated with pauses in volcanic activity throughout the Middle to early Late Ordovician over a wide area in the western province, culminating in the mineralisation at Cargo and Copper Hill near Molong. Volcanism in the eastern province of the Molong Volcanic Belt was continuous from at least Darriwilian to latest Ordovician time. Here, detrital hydrothermal vein quartz and volcanic quartz and felsic detritus are distributed through late Middle and early Late Ordovician turbidites of the Weemalla Formation. The possible existence of cycles in the source area like those of the Fairbridge Volcanics is masked by the distal nature of these deposits. Vein formation occurred in both provinces from late Middle Ordovician to early Late Ordovician, long before the formation of the world‐class mineral deposit at Cadia associated with the latest Ordovician Cadia Monzonite.  相似文献   

SHRIMP zircon age for an Early Cambrian dolerite dyke: An intrusive phase of the Antrim Plateau Volcanics of northern Australia     

L. M. Hanley  M. T. D. Wingate 《Australian Journal of Earth Sciences》2013,60(6):1029-1040

The Antrim Plateau Volcanics, Australia's largest Phanerozoic flood‐basalt province, originally covered an area of at least 300 000 km² across northern Australia. Stratigraphic constraints indicate that the Antrim Plateau Volcanics are of Early Cambrian age (ca 545–509 Ma), although previous attempts to date the Antrim basalts by radiometric methods have been inconclusive. We present an ion microprobe U–Pb zircon age of 513 ± 12 Ma for the ～250 km‐long Milliwindi dolerite dyke in the west Kimberley. The dolerite is geochemically identical to basalts of the Antrim Plateau Volcanics, and was probably a feeder dyke for basalts that have since been eroded. It is suggested that the Antrim Plateau Volcanics extended hundreds of kilometres further to the west than recognised previously and may have once covered part of the Kimberley block.  相似文献   

Wildfire preparedness,community cohesion and social–ecological systems     

Tim Prior  Christine Eriksen 《Global Environmental Change》2013,23(6):1575-1586

The consequences of wildfires are felt in susceptible communities around the globe on an annual basis. Climate change predictions in places like the south-east of Australia and western United States suggest that wildfires may become more frequent and more intense with global climate change. Compounding this issue is progressive urban development at the peri-urban fringe (wildland–urban interface), where continued infrastructure development and demographic changes are likely to expose more people and property to this potentially disastrous natural hazard. Preparing well in advance of the wildfire season is seen as a fundamental behaviour that can both reduce community wildfire vulnerability and increase hazard resilience – it is an important element of adaptive capacity that allows people to coexist with the hazardous environment in which they live. We use household interviews and surveys to build and test a substantive model that illustrates how social cohesion influences the decision to prepare for wildfire. We demonstrate that social cohesion, particularly community characteristics like ‘sense of community’ and ‘collective problem solving’, are community-based resources that support both the adoption of mechanical preparations, and the development of cognitive abilities and capacities that reduce vulnerability and enhance resilience to wildfire. We use the results of this work to highlight opportunities to transfer techniques and approaches from natural hazards research to climate change adaptation research to explore how the impacts attributed to the social components of social–ecological systems can be mitigated more effectively.  相似文献   

Impact of benzyl butyl phthalate on shoaling behavior in Fundulus heteroclitus (mummichog) populations     

《Marine environmental research》2013

Fundulus heteroclitus preference for association with familiar conspecifics of similar body length was impacted by benzyl butyl phthalate (BBP); this was found to be a statically significant result with a p < 0.0001. When presented with equally sized shoals consisting of either large or small fish, the majority of unexposed (84%) and acetone exposed control (82%) fish selected the shoal of large fish. A small number of control fish chose either the shoal of small fish (6% and 10%) or the neutral zone (10% and 8%) where they were clear morphological outliers. Fish exposed to 0.1 mg/L BBP exposure daily for four weeks selected the shoal of small fish more often than unexposed or acetone controls (7.5- and 4.5-fold respectively). They also remained in the neutral zone and displayed agitation at levels more than twice that of control. Agitation and shoal choice disruption are quantifiable behavioral responses that support the use of F. heteroclitus as a model for detecting sub-lethal BBP exposure.  相似文献   

Soothing Breezes? Island perspectives on climate change and migration     

John Connell 《The Australian geographer》2013,44(4):465-480

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Crustal structure of the Ordovician Macquarie Arc,Eastern Lachlan Orogen,based on seismic‐reflection profiling     

R. A. Glen  R. J. Korsch  N. G. Direen  L. E. A. Jones  D. W. Johnstone  K. C. Lawrie 《Australian Journal of Earth Sciences》2013,60(2):323-348

In the Eastern Lachlan Orogen, the mineralised Molong and Junee‐Narromine Volcanic Belts are two structural belts that once formed part of the Ordovician Macquarie Arc, but are now separated by younger Silurian‐Devonian strata as well as by Ordovician quartz‐rich turbidites. Interpretation of deep seismic reflection and refraction data across and along these belts provides answers to some of the key questions in understanding the evolution of the Eastern Lachlan Orogen—the relationship between coeval Ordovician volcanics and quartz‐rich turbidites, and the relationship between separate belts of Ordovician volcanics and the intervening strata. In particular, the data provide evidence for major thrust juxtaposition of the arc rocks and Ordovician quartz‐rich turbidites, with Wagga Belt rocks thrust eastward over the arc rocks of the Junee‐Narromine Volcanic Belt, and the Adaminaby Group thrust north over arc rocks in the southern part of the Molong Volcanic Belt. The seismic data also provide evidence for regional contraction, especially for crustal‐scale deformation in the western part of the Junee‐Narromine Volcanic Belt. The data further suggest that this belt and the Ordovician quartz‐rich turbidites to the east (Kirribilli Formation) were together thrust over ?Cambrian‐Ordovician rocks of the Jindalee Group and associated rocks along west‐dipping inferred faults that belong to a set that characterises the middle crust of the Eastern Lachlan Orogen. The Macquarie Arc was subsequently rifted apart in the Silurian‐Devonian, with Ordovician volcanics preserved under the younger troughs and shelves (e.g. Hill End Trough). The Molong Volcanic Belt, in particular, was reworked by major down‐to‐the‐east normal faults that were thrust‐reactivated with younger‐on‐older geometries in the late Early ‐ Middle Devonian and again in the Carboniferous.  相似文献   

A comparison of the impact of ‘seagrass-friendly’ boat mooring systems on Posidonia australis     

《Marine environmental research》2013

Permanent boat moorings have contributed to the decline of seagrasses worldwide, prompting the development of ‘seagrass-friendly’ moorings. We contrasted seagrass cover and density (predominantly Posidonia australis) in the vicinity of three mooring types and nearby reference areas lacking moorings in Jervis Bay, Australia. We examined two types of ‘seagrass-friendly’ mooring and a conventional ‘swing’ mooring. ‘Swing’ moorings produced significant seagrass scour, denuding patches of ∼9 m radius. Seagrass-friendly ‘cyclone’ moorings produced extensive denuded patches (average radius of ∼18 m). Seagrass-friendly ‘screw’ moorings, conversely, had similar seagrass cover to nearby reference areas. Our findings reinforce previous work highlighting the negative effects of ‘swing’ and ‘cyclone’ moorings. In contrast, the previously unstudied ‘screw’ moorings were highly effective. We conclude that regular maintenance of moorings and the monitoring of surrounding seagrass are required to ensure that ‘seagrass-friendly’ moorings are operating effectively. This is important, as following damage Posidonia will take many decades to recover.  相似文献   

Daily rainfall projections from general circulation models with a downscaling nonhomogeneous hidden Markov model (NHMM) for south‐eastern Australia     

Guobin Fu  Stephen P. Charles  Sergey Kirshner 《水文研究》2013,27(25):3663-3673

An ensemble of stochastic daily rainfall projections has been generated for 30 stations across south‐eastern Australia using the downscaling nonhomogeneous hidden Markov model, which was driven by atmospheric predictors from four climate models for three IPCC emissions scenarios (A1B, A2, and B1) and for two periods (2046–2065 and 2081–2100). The results indicate that the annual rainfall is projected to decrease for both periods for all scenarios and climate models, with the exception of a few scenarios of no statistically significant changes. However, there is a seasonal difference: two downscaled GCMs consistently project a decline of summer rainfall, and two an increase. In contrast, all four downscaled GCMs show a decrease of winter rainfall. Because winter rainfall accounts for two‐thirds of the annual rainfall and produces the majority of streamflow for this region, this decrease in winter rainfall would cause additional water availability concerns in the southern Murray–Darling basin, given that water shortage is already a critical problem in the region. In addition, the annual maximum daily rainfall is projected to intensify in the future, particularly by the end of the 21st century; the maximum length of consecutive dry days is projected to increase, and correspondingly, the maximum length of consecutive wet days is projected to decrease. These changes in daily sequencing, combined with fewer events of reduced amount, could lead to drier catchment soil profiles and further reduce runoff potential and, hence, also have streamflow and water availability implications. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Peat mounds of southwest Tasmania: Possible origins     

M. K. Macphail  M. Pemberton  G. Jacobson 《Australian Journal of Earth Sciences》2013,60(5):667-677

Small mounds of peat rise several metres above the level of the water‐table at Melaleuca Inlet and Louisa Plains on the buttongrass plains in southwest Tasmania. Possible origins of the peat mounds have been explored by pollen analysis and radiocarbon dating of a set of samples taken from a vertical section of one peat mound at Melaleuca. The peat accumulation is entirely of Holocene age although the mound is underlain by sapric peats preserving a cold climate palynoflora of probable Late Pleistocene age. Peats at and near the base of the mound accumulated under a heath sedgeland during the earliest Holocene while after about 7630 a BP the peat‐forming vegetation was shrub‐dominated. The radiocarbon data indicate two main phases of overall peat accumulation, between 7630 and 5340 a BP (Middle Holocene) and between 4450 and 450 a BP (Late Holocene), that were interrupted by a wildfire which burnt into the surface peats. The maintenance of high surface and internal levels of moisture almost certainly was the critical factor behind the low incidence of in situ fires burning into the surface peats on the mound. The perennial influx of groundwater below the mound is a possible origin that fits well with our observations, although the expansion and contraction of soils cannot be discounted as an initiating factor. Enhanced nutrient input from birds may have helped promote growth in the peat‐forming communities. The data do not support the mounds being eroded remnants of a former blanket peat cover or being due to periglacial activity. The peat mounds of southwest Tasmania deserve maximum protection because of their rarity in the Australian landscape and, it seems, elsewhere.  相似文献   

Observation and analysis of mixing in a tidal and wind-mixed coastal region     

《Ocean Modelling》2011,38(3-4):65-84

In this article, the authors first present oceanic observations collected in a coastal area in May 2007. The evolution of temperature profiles exhibits a very clear atmospheric heating signal and is used to study mixing. Modelled atmospheric fluxes are evaluated using the oceanic measurements. The K-profile parameterisation (KPP) is chosen to identify the most important mixing processes and its parameters are tuned to minimise differences with respect to the observations.It is found that:• the tuned KPP is able to accurately represent the effect of mixing in this case;• surface and bottom boundary layers, as well as interior shear instability mixing processes all play an important role in the observed evolution of the temperature profile, the bottom boundary being the source of the most intense mixing;• the nonlocal effects in KPP (activated during nocturnal cooling periods) have to be switched off for a better agreement.  相似文献