Distribution and possible sources of organochlorine residues in sediments of a large urban estuary,Port Jackson,Sydney     

G. F. Birch  S. E. Taylor 《Australian Journal of Earth Sciences》2013,60(4):749-756

Sydney Harbour is surrounded by a large capital city of about four million people and its highly urbanised (86%) catchment supports a substantial industrial base and an extensive transport infrastructure. Large commercial and naval ports occupy the waterway and the harbour is an important recreational area. Surficial sediment in Sydney Harbour contains high concentrations of PCBs, HCB, total chlordane, total DDT, aldrin, dieldrin, heptachlor and heptachlor‐epoxide, but low concentrations of lindane. PCBs, total chlordane, and to a lesser extent dieldrin, are most elevated in sediment in creeks on the southern shores of the harbour suggesting sources within older, highly urbanised/industrialised catchments of western‐central Sydney. There are high concentrations of total DDT and HCB in sediments of the upper harbour and Homebush Bay suggesting that chemical industries on the shores of the estuary in this area are sources of these contaminants. Although no sediment quality guidelines apply in Australia, empirically derived biological effects criteria suggest that sediment over extensive areas of Sydney Harbour may have an adverse impact on biota. Especially of concern are sediments containing high concentrations of chlordane and DDT.  相似文献   

Sunrise Hill unconformity: A newly discovered regional hiatus between Archaean granites and greenstones in the northeastern Pilbara Craton     

P. R. Dawes  R. H. Smithies  J. Centofanti  D. C. Podmore 《Australian Journal of Earth Sciences》2013,60(6):635-639

Contacts between Archaean granites and greenstones in the northeastern part of the Pilbara Craton have been described as intrusive and tectonic. New field observations in the Shay Gap region demonstrate that greenstones of the Gorge Creek Group unconformably overlie the Muccan and Warrawagine batholiths. Regionally, the unconformity is marked by a persistent but relatively thin basal clastic sequence, locally with a granite boulder conglomerate, overlain by ore‐bearing banded iron‐formation, fine‐grained clastic rocks and chert. The granite basement is dated at 3443 ± 6 Ma. The precise age of the hiatus is unknown but its maximum effect might have been the removal of a substantial thickness of Early to Middle Archaean strata.  相似文献   

Transient two-dimensional groundwater flow     

V. U. NGUYEN  A. J. RAUDKIVI 《水文科学杂志》2013,58(4):427-438

ABSTRACT

A set of simple analytical solutions are presented for estimation of drawdowns and groundwater flow rates into two-dimensional excavation, such as those in open-cut strip mines, for confined, leaky and unconfined aquifers.  相似文献   

Matt Wilson structure: record of an impact event of possible Early Mesoproterozoic age,Northern Territory     

I. P. Sweet  P. W. Haines  K. Mitchell 《Australian Journal of Earth Sciences》2013,60(4-5):675-688

The Matt Wilson structure is a circular 5.5 km-diameter structure in Early Mesoproterozoic or Neoproterozoic rocks of the Victoria Basin, Northern Territory. It lies in regionally horizontal to gently dipping Wondoan Hill and Stubb Formations (Tijunna Group) and Jasper Gorge Sandstone (Auvergne Group). An outer circumferential syncline with dips of 5?–?40° in the limbs surrounds an intermediate zone with faulted sandstone displaying horizontal to low dips, and a central steeply dipping zone about 1.5 km across. Several thrust faults in the outer syncline appear to indicate outward-directed forces. The central zone, marked by steeply dipping to overturned Tijunna Group and possibly Bullita Group sandstone and mudstone, indicates uplift of at least 300 m. The rocks are intensely fractured with some brecciation, and contain numerous planar to subtly undulating surfaces displaying striae which resemble shatter cleavage. Thin-sections of sandstone from the central area show zones of intense microbrecciation and irregular and planar fractures in quartz, but no melt-rocks have been identified. The planar fractures occur in multiple intersecting parallel sets typical of relatively low-level (5?–?10 GPa) shock-pressure effects. Alternative mechanisms, i.e. igneous intrusion, carbonate collapse, diapirism and regional deformation processes, have been discounted. The circular nature, central uplift, faulting, shatter features and planar fractures are all consistent with an impact origin. The Matt Wilson structure is most likely a deeply eroded impact structure in which the more highly shocked rocks of the original crater floor have been removed by erosion. Estimates of the age of the Auvergne and Tijunna Groups range from Early Mesoproterozoic (which we favour) to Late Neoproterozoic. Early Cambrian Antrim Plateau Volcanics near the impact structure show no signs of impact effects, allowing the age of impact to be constrained between Early Mesoproterozoic and Early Cambrian. The presence of widespread soft-sediment deformation features, apparently confined to a single horizon in the Saddle Creek Formation some 700?–?1000 m stratigraphically higher in the Auvergne Group than the rocks at the impact site, and apparently increasing in thickness towards the Matt Wilson structure, lead us to speculate that this probable event horizon is related to the impact event: if correct the impact occurred during deposition of the Saddle Creek Formation.  相似文献   

Engineering characteristics and uses of duricrusts in Australia     

G. H. McNally 《Australian Journal of Earth Sciences》2013,60(6):535-547

The uses and shortcomings of duricrusts (ferricrete, calcrete and silcrete) in engineering construction (as used for road‐base, aggregate, foundation materials and aquifers) are reviewed. Australian production of these materials represents about one‐third of all unprocessed road‐base and they are especially important as pavement courses for lightly trafficked, low‐cost rural and outback roads. However, duricrusts are regarded as marginal materials at best because of their typically poor grading, particle unsoundness, high fines plasticity, and absorption of water and bitumen. These materials are used because they are available locally in areas that are otherwise lacking in hard rock materials, such as deeply weathered and sedimentary rock terrains. The weathering profiles of which they form part are characterized by high permeability (despite being clay‐rich), variable cementation, low compressibility and a tendency to become weaker with depth. Although the more indurated layers are unrippable, they are also difficult to blast. Pedogenic (nodular) duricrusts were formerly sought for natural road‐base, because they occur widely and require only rudimentary processing. However, well‐cemented groundwater (vadose) duricrusts are now the preferred deposits, even though they require crushing and screening. Ferricrete is the most widely exploited of the duricrusts for engineering purposes, especially in northern and southwestern Australia, although calcrete is important in South Australia and in the Murray Basin. Silcrete is only a minor source of aggregate and road‐base, mainly in western Queensland.  相似文献   

Paleoclimate studies and natural-resource management in the Murray-Darling Basin I: past,present and future climates     

K. Mills  P. Gell  P. P. Hesse  R. Jones  P. Kershaw  R. Drysdale 《Australian Journal of Earth Sciences》2013,60(5):547-560

This paper provides an incisive review of paleoclimate science and its relevance to natural-resource management within the Murray-Darling Basin (MDB). The drought of 1997–2010 focussed scientific, public and media attention on intrinsic climate variability and the confounding effect of human activity, especially in terms of water-resource management. Many policy and research reviews make statements about future planning with little consideration of climate change and without useful actionable knowledge. In order to understand future climate changes, modellers need, and demand, better paleoclimate data to constrain their model projections. Here, we present an insight into a number of existing long-term paleoclimate studies relevant to the MDB. Past records of climate, in response to orbital forcing (glacial–interglacial cycles) are found within, and immediately outside, the MDB. High-resolution temperature records, spanning the last 10⁵ years, exist from floodplains and cave speleothems, as well as evidence from lakes and their associated lunettes. More recently, historical climate records show major changes in relation to El Niño–Southern Oscillation cycles and decadal shifts in rainfall regimes. A considerable body of research currently exists on the past climates of southeastern Australia but, this has not been collated and validated over large spatial scales. It is clear that a number of knowledge gaps still exist, and there is a pressing need for the establishment of new paleoclimatic research within the MDB catchment and within adjacent, sensitive catchments if past climate science is to fulfil its potential to provide policy-relevant information to natural-resource management into the future.  相似文献   

Market access,population density,and socioeconomic development explain diversity and functional group biomass of coral reef fish assemblages     

Tom D. Brewer  Joshua E. Cinner  Rebecca Fisher  Alison Green  Shaun K. Wilson 《Global Environmental Change》2012,22(2):399-406

There is overwhelming evidence that many local-scale human activities (e.g. fishing) have a deleterious effect on coral reef fish assemblages. Our understanding of how broad social phenomena (e.g. socioeconomic development) affect the diversity and function of coral reef fish assemblages however, is still poor. Here, we use structural equation models to reveal how human population density, socioeconomic development, and market access affect fishing pressure and coral cover to, in turn, explain the diversity and biomass of key functional groups of reef fish assemblages within Solomon Islands. Fishing pressure is predominantly driven by both market access and local population density, and has a clear negative effect on the diversity and function of coral reef fishes. The strong positive effect of market access on fishing pressure makes clear the importance of understanding social-ecological linkages in the context of increasingly connected societies. This study highlights the need to address broad social phenomena rather than focusing on proximate threats such as fishing pressure, to ensure the continued flow of coral reef goods and services in this time of rapid global social and environmental change.  相似文献   

Preliminary 3–D geological model of the Kalgoorlie region,Yilgarn Craton,Western Australia,based on deep seismic‐reflection and potential‐field data     

B. R. Goleby  R. J. Korsch  T. Fomin  B. Bell  M. G. Nicoll  B. J. Drummond 《Australian Journal of Earth Sciences》2013,60(6):917-933

The granite‐greenstone terranes of the Eastern Goldfields Province, Yilgarn Craton, Western Australia, are a major Australian and world gold and nickel source. The Kalgoorlie region, in particular, hosts several world‐class gold deposits. To attempt to understand why these deposits occur where they do, it is important to understand the crustal architecture in the region and how the major mineral systems operate in this architecture. One way to understand these relationships is to develop a detailed 3–D geological model for the region. The best method to map the 3–D geometry of major geological structures is by acquisition and interpretation of seismic‐reflection profiles. To contribute to this aim, a grid of deep seismic‐reflection traverses was acquired in 1999 to examine the 3–D geometry of the region in an area including the Kalgoorlie mineral region and mineral fields to the north and west. This grid was tied to the 1991 regional deep seismic traverse and 1997 high‐resolution seismic profiles in the same region. The grid covers an area measuring approximately 50 km wide by 50 km long and extended to a depth of approximately 50 km (below the base of the crust in this region). The resulting 3–D geological model was further constrained by both surface geological data and geophysical interpretations, with the seismic interpretations themselves also constrained by gravity and magnetic modelling. The 3–D model was used to investigate the geometric relationships between the major faults and shear zones in the area, the relationship between the granite‐greenstone succession and the basement, and the spatial relationships between the greenstones and the granites. Interpretation of the grid of seismic lines and construction of the 3–D geological model confirmed the existence of the detachment surface and led to the recognition that the granite‐greenstone contact usually occurs at a much shallower level than the detachment. Also, west‐dipping faults in the vicinity of the Golden Mile, including the Abattoir Shear through to Boulder‐Lefroy Fault, appear to be more important than previously thought in controlling the structure of that area. An antiformal thrust stack occurs beneath a triangle zone centred on the Golden Mile. The Black Flag Group was deposited in a probable extensional setting, and late extension was also probably more important than previously thought. The granite‐gneiss domes were uplifted by the formation of antiformal thrust stacks at depth beneath them.  相似文献   

Drained cavity expansions in soils of finite radial extent subjected to two boundary conditions     

Mohammad Pournaghiazar  Adrian R. Russell  Nasser Khalili 《国际地质力学数值与分析法杂志》2013,37(4):331-352

The problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Cosmogenic activation in germanium and copper for rare event searches     

《Astroparticle Physics》2011,34(5-6):316-329

Experiments looking for rare events like the direct detection of dark matter particles or the nuclear Double Beta Decay are operated in deep underground locations, to suppress or very effectively reduce the effect of cosmic rays; but cosmogenic activation produced at sea level in detectors and other materials can become a serious hazard for them. Copper and germanium are very frequently used in this kind of experiments requiring an ultra-low radioactive background and therefore have been chosen as activation targets in this work. First, the excitation functions for relevant induced long-lived radioactive isotopes have been estimated; special care has been taken in using those calculations giving the best agreement with measured production cross-sections and in distinguishing production by neutrons or by protons when relevant and possible. Then, the corresponding rates of production of the nuclides in natural and enriched (86% ⁷⁶Ge and 14% ⁷⁴Ge) germanium and copper have been evaluated considering two different cosmic ray spectra. Comparison of the obtained activation yields at surface with all the known previous results (based either on calculations or experiments) has allowed to draw conclusions on the general methodology for evaluating cosmogenic activation.  相似文献