Seismic reflection evidence for the evolution of the Camden Syncline and Lapstone Structural Complex,central Sydney Basin,Australia     

A. Bray  P. Hatherly  C. L. Fergusson 《Australian Journal of Earth Sciences》2013,60(7):993-1004

The Camden Syncline and the Lapstone Structual Complex are two major geological features of the central Sydney Basin. We have interpreted over 500 km (45 lines) of an unpublished recenty reprocessed seismic dataset as a means to elucidating the evolution of both features. Major horizons observed in the seismic data have been described and correlated with significant tectonic events that shaped the formation of the greater Sydney–Gunnedah–Bowen Basin; namely Early Permian extension, mid-Permian passive thermal subsidence and Late Permian to mid-Triassic foreland loading. Horizon mapping shows that the Camden Syncline is a broad north-northeast plunging structure whose western limb is truncated by the north–south trending faults and folds of the Lapstone Structural Complex. Furthermore, isochron maps reveal that the Late Permian to mid-Triassic sedimentary succession thickens towards the axis of the Camden Syncline, thus confirming it's role as a depocentre during this period of basin evolution. No abrupt thickening is observed in the Late Permian to mid-Triassic sedimentary succession in the vicinity of the Lapstone Structural Complex indicating that the Lapstone Structural Complex was formed subsequent to the deposition of the Permian–Triassic Sydney Basin sedimentary succession. Furthermore, our interpretation of the reprocessed seismic data confirms that the major structural style of the Lapstone Structural Complex is that of west dipping reverse faults and east facing monoclines.  相似文献   

Age and composition of dykes emplaced before and during the opening of the Tasman Sea—source implications     

R. Offler  H. Zwingmann  J. Foden  F. L. Sutherland  I. T. Graham 《Australian Journal of Earth Sciences》2013,60(8):1129-1144

Abstract

Dykes are common in the wave-cut platforms along the coast from Newcastle to Sydney. According to some authors, they may be related to the opening of the Tasman Sea that commenced ca 84?Ma ago. However, there are few detailed radiogenic dating and geochemical studies to evaluate this. We attempt to resolve this by K–Ar dating of plagioclase in and geochemical studies of, basaltic dykes intruding Permo-Triassic sequences on the wave-cut platforms and Carboniferous and Permo-Triassic sequences inland. The plagioclase separated from the dykes give K–Ar ages ranging from 266 to 53?Ma with the majority older than 84?Ma indicating that most dykes were emplaced before the Tasman Seafloor formation. The dykes are generally mildly alkaline, high-Ti basalts; fewer are tholeiitic and calc-alkaline, low-Ti basalts. Strongly light rare earth element (LREE)-enriched patterns typify the former and flat, LREE-depleted or slightly to moderately enriched LREE patterns, the latter. High-Ti basalts have ocean-island-basalt-like and low-Ti basalts, calc-alkaline or mid-ocean ridge basalt (MORB)-like patterns. Most high-Ti and some low-Ti basalts show plume-like characteristics, others N-type MORB and arc-like characteristics. Dykes intruding the Carboniferous sequences show a distinct contamination signature that could be crustal or due to subduction-related metasomatism of the subcontinental lithospheric mantle. The sources of the basaltic magmas vary substantially and in places changes with time. All alkali basalts are derived from enriched asthenospheric sources at varying depths (90–147?km) and most tholeiitic, low-Ti basalts have been extracted from asthenospheric and depleted asthenospheric–lithospheric sources indicating substantial compositional heterogeneity of the mantle. Further, Nd model ages varying from Neoproterozoic (940–580?Ma) to Paleozoic (460–370?Ma) suggest variation in the age of mantle sources for the basalts.  相似文献   

The source and distribution of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofurans in sediments of Port Jackson, Australia     

Birch GF  Harrington C  Symons RK  Hunt JW 《Marine pollution bulletin》2007,54(3):295-308

Concentrations of polychlorinated dibenzo-p-dioxins (dioxins)(PCDDs) and polychlorinated dibenzofurans (PCDFs)(furans) in sediments from Port Jackson ranged from 32 to 4352 pg WHO-TEQ DF g(-1)dw with a mean of 712 pg g(-1)dw. Maximum total dioxins plus furans concentrations in this sediment was 6,290,000 pg g(-1)dw, which is the highest recorded in Australia and among the highest reported for sediment globally. Permanent bans were placed on fin fishing and prawn trawling in February, 2006 for the whole estuary, based on dioxin tissue burdens. A distinct congener profile corresponded to chemicals known to have been produced by industry on the shores of Homebush Bay in the upper estuary. These chemicals are being dispersed extensively and exceed pre-anthropogenic concentrations in even distant, less developed parts of the harbour. Remediation of sediments is currently being undertaken, with the intention of containing dispersion of dioxins and reducing body burdens in fin fish and prawn populations.  相似文献   

Changing retail structure in Southern Sydney     

《The Australian geographer》1991,22(1):57-66

Analysis of the retail structure in three local government areas in southern Sydney revealed many changes over the period 1969–1989: the number of establishments grew by more than 20 per cent despite a significant population decline; there was considerable evidence of the suburbanisation of the professions; and the composition of shopping centres reflected changing suburban lifestyles, notably as regards an increased concern for eating out, fitness and health, and personal services. Over time, the hierarchy of shopping centres became less clear‐cut and more attenuated. The geographical pattern of growth and decline suggests that the retail structure of the area is becoming increasingly complex.  相似文献   

Low‐grade metamorphism of mafic lavas,Upper Permian Broughton Formation,Sydney Basin     

P. F. Carr  J. W. Pemberton  E. Nunan 《Australian Journal of Earth Sciences》2013,60(6):839-849

Coexisting primary minerals and hydrous alteration minerals in basalt lavas of the Upper Permian Broughton Formation of the Sydney Basin are indicative of the involvement of a hydrothermal fluid phase during low‐grade metamorphism. Variation and zonation of alteration phases in vesicles and vugs indicate that the alteration minerals developed in response to several episodes of precipitation, with early CO₂‐rich fluids producing assemblages rich in calcite and chlorite‐smectite while later CO₂‐poor fluids precipitated Ca‐zeolites, prehnite and pumpellyite. Vesicular parts of flows typically show much higher contents of alteration minerals than more massive parts of the same flow, but no systematic increase in either the style or intensity of alteration with increasing depth in the lava pile is evident. The presence of Ca‐zeolites, prehnite, pumpellyite and rare epidote suggests uppermost zeolite facies to lowermost prehnite‐pumpellyite facies metamorphism. Stability relationships of the metamorphic phases based on experimental and theoretical studies, used in conjunction with measured parameters for modern geothermal systems, indicate a peak metamorphic temperature of ～200–230°C while the extant stratigraphy indicates that the maximum depth of burial was ～ 1200 m. Alteration developed in response to circulation of hot, aqueous fluids generated by thermal convection cells associated with the Permian lavas and/or a large buried intrusion.  相似文献   

Clast shape and textural associations in peperite as a guide to hydromagmatic interactions: Upper Permian basaltic and basaltic andesite examples from Kiama,Australia     

M. G. Doyle 《Australian Journal of Earth Sciences》2013,60(1):167-177

Upper Permian shallow marine siltstone and sandstone units of the Broughton Formation are intercalated with basaltic and basaltic andesite sheets at Kiama, New South Wales. Parts of the two sheets examined in this study display peperite texture. The lower example (Blow Hole Latite Member) can be divided into two units with peperitic contacts suggesting their intrusion into wet unconsolidated sediments of the overlying Kiama Sandstone Member. The Bumbo Latite Member overlies the Kiama Sandstone Member and has been interpreted by previous workers as a lava. Well‐developed columnar joints cut the interior of the sheets. Along contacts with sedimentary facies and peperitic dykes which penetrate the sheets, columnar joints merge into a several metre‐wide zone of blocky jointing, pseudo‐pillows and hyaloclastite. In peperitic facies, sandstone or siltstone fills joints and fractures that define pseudo‐pillows, polyhedral joint blocks and columns (closely packed fabric) or sediment matrix‐rich breccia contains fragments and apophyses of basalt and basaltic andesite (dispersed fabric). Along some contacts, peperite with dispersed fabric passes through a zone of closely packed peperite into coherent facies. Alternatively, closely packed peperite passes directly into coherent facies. Examples of peperite with more than one clast type (globular, blocky, platy), and involving sedimentary matrix of constant grain‐size, are common. In some examples, globular surfaces formed during an early, low‐viscosity phase of magma emplacement into wet sediment. Planar and curviplanar fractures cut some globular surfaces suggesting that these formed slightly later as the magma became more viscous (cooler) and/or vapour films at the magma‐sediment interface broke down. However, the complexities of peperite, in respect to clast types, abundances and distribution, as well as grainsize and structures in the sedimentary component, suggest that a spectrum of fragmentation and mixing processes were involved in fragmenting the sheets. Many peperitic domains include poorly and strongly vesicular parts, resulting in apparent polymictic breccias. Vesiculation of the sheets is interpreted to have occurred in two phases: an early degassing of primary magmatic volatiles and a later, scoria‐forming event, both of which progressed as the magma mixed with unconsolidated sediment. During the later phase, magma incorporated limited amounts of steam from the wet sediment and a vesicular front propagated out into the magmatic component. Confining pressures were insufficient to prevent vesiculation of the magma or to suppress fluidisation of the host sediment along magma‐sediment contacts, but large enough to inhibit large‐scale steam explosivity. Displacement of sediment along contacts may have reduced confining pressures sufficiently to promote vaporisation of pore water, and induce local vesiculation of the magma.  相似文献   

Relationship between the technical parameters of cokes produced from blends of three Polish coals of different coking ability     

A. Koszorek  M. Krzesi&#x;ska  S. Pusz  B. Pilawa  B. Kwieci&#x;ska 《International Journal of Coal Geology》2009,77(3-4):363-371

The demand for metallurgical coke for blast furnaces is forcing the coking industry to look for new sources of coking coals. The physical and chemical parameters of coals used in coking blends determine the quality (reactivity and strength) of the finished cokes. This study examines the technical properties of the cokes produced from various blends of three Polish coals with different coking. These coals were collected from three mines: Zofiówka, Szczygłowice, and Krupiński (Upper Silesian Coal Basin, Poland). The coal charges were coked in the laboratory scale, at temperatures of up to 1000 °C, in an inert atmosphere. The coke reactivity (index CRI) and the coke strength after reaction (CSR) were measured and correlated to the properties of parent coals using statistical analysis. The result of this study shows strong relationships between the concentration of the best coking coal (Zofiówka) in the blend and the CRI and CSR of the resulting coke. The CRI and CSR parameters for cokes obtained from single coals and from their blends show the additive character. This study also confirms the linear relationship between CRI and CSR parameters of the cokes.  相似文献   

Industry Clusters and Sydney's ITT Sector: northern Sydney as ‘Australia's Silicon Valley’?     

Glen Searle 《The Australian geographer》2005,36(2):145-169

This paper examines the claim that the North Ryde–North Sydney arc is Australia's ‘Silicon Valley’, seeking firstly to identify the empirical validities behind the claim, and secondly to ask how the documented patterns might be explained. The paper evidences the fact that this area indeed provides the pre-eminent site for Australia's information technology and telecommunications (ITT) sector. However, examination of this industry suggests that its expansion in Sydney has been motivated primarily by the increasing centrality of advanced producer services within the high-order business sector. It is Sydney's attributes for multinational business, as opposed to the propulsive dynamics of local clustering per se, which appears to explain the spatial concentration of these activities. Thus, it is the urbanisation economies of Sydney more than the localisation economies of the ITT sector which account for the growth of this sector in the city. Nevertheless, localisation economies are sporadically significant, suggesting that Sydney's ITT sector is to a certain extent a hybrid product of the two types of economies.  相似文献   

The Response of Aboriginal Burning Practices to Population Levels and El Niño–Southern Oscillation Events during the mid- to late-Holocene: a case study from the Sydney Basin using charcoal and pollen analysis     

Manu P. Black 《The Australian geographer》2007,38(1):37-52

Pollen and macroscopic charcoal have been analysed from a sedimentary sequence representing approximately 6100 years from a site within Wollemi National Park. This is located to the north-west of Sydney and forms a part of the Greater Blue Mountains World Heritage Area. The overall aim of the work was to examine the prehistoric interrelationships between vegetation, fire and human activity. There were relatively minor changes in the vegetation over the last ～6000 years, perhaps reflecting the climate- and fire-resilient nature of the sclerophyllous vegetation found on Hawkesbury Sandstone throughout the Sydney Basin. Casuarinaceae declined in the late Holocene, a trend that has been detected in numerous palaeoecological studies throughout south-eastern Australia. This decline was unrelated to fire, which has been a persistent feature at the site over the entire analysed sequence. The fire regime at the site changed from 5.7 ka, which is interpreted as reflecting the onset of increased climatic variability associated with El Niño-Southern Oscillation (ENSO) events. Another dramatic change in the fire regime occurred at 3 ka, which was coeval with archaeological changes in the region. It is possible that the change in fire activity from 3 ka represented an alteration to Aboriginal management strategies associated with an increasing population and/or the increased risk of conflagrations in an ENSO-dominated climate.  相似文献   

A Comparison of Charcoal and Archaeological Information to Address the Influences on Holocene Fire Activity in the Sydney Basin     

S. D. Mooney  M. Webb  V. Attenbrow 《The Australian geographer》2007,38(2):177-194

The influence of Aboriginal people on fire activity and hence the vegetation of Australia has long been debated. This study aimed to document the local fire activity of the Holocene in the catchment of a small freshwater reed swamp located in the Sydney Basin and to compare this with nearby archaeological evidence; including artefact discard rates and the number of base camps and activity locations used through time. This archaeological evidence was used as an index of human activity through time to assess anthropogenic influences on fire activity. Charcoal (>250 µm) was quantified in a radiocarbon-dated sediment core from Griffith Swamp covering ～6000 calibrated years BP. A substantial increase in fire activity was found from ～3000 years BP and a lesser increase approximately 700 years ago. The change in fire activity at ～3000 years BP was approximately coeval with changes in archaeological evidence from Upper Mangrove Creek, suggesting either greater human presence in the landscape or altered subsistence and land-use strategies. Fire frequency in the catchment of Griffith Swamp peaked at about eight episodes per century, perhaps in response to environmental change that promoted both increased human activity and a higher natural fire frequency. This study provides an extended temporal perspective on fire and humans in this landscape, demonstrating how palaeoecology can provide practical information for the contemporary management of such fire-prone ecosystems.  相似文献