Geostatistics Wollongong '96: Volumes 1 and 2 By E. Y. Baafi and N. A. Schofield (eds.)     

James Russell Carr 《Mathematical Geosciences》1999,31(6):743-744

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Letter to the Editor     

James Russell Carr 《Mathematical Geology》2000,32(4):513-515

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The evolution of coastal barrier systems: a case study of the Middle-Late Pleistocene Wilderness barriers,South Africa     

Mark D. Bateman  Andrew S. Carr  Adam C. Dunajko  Peter J. Holmes  David L. Roberts  Sue J. McLaren  Robert G. Bryant  Margaret E. Marker  Colin V. Murray-Wallace 《Quaternary Science Reviews》2011,30(1-2):63-81

Barrier systems contain lengthy, but complex, records of long-term environmental fluctuations. The Wilderness embayment, South Africa, contains a system of shore-parallel barriers reaching up to 200 m above modern sea level. This study reports the results of chronological, topographical (both on- and off-shore), sedimentological and micromorphological analyses within the Wilderness embayment. Sixty-one new luminescence ages from sixteen sites in unconsolidated dunes and three separate barriers are presented which, when combined with previously published luminescence ages from the area, provide a high-resolution chronological framework for the emplacement and evolution of the barrier system. The preserved barriers have been constructed within at least the last two glacial–interglacial cycles with notable phases between 241–221 ka, 159–143 ka, 130–120 ka, 92–87 ka and post 6 ka. Multiple phases of barrier construction occurred during sea-level highstands, with sediment deposition on each individual barrier occurring over at least two interglacials. Holocene evolution of the system sheds light on earlier events, with dune preservation occurring only during early regression from the Mid-Holocene highstand. Tectonic stability at Wilderness allowed glacio-eustatically formed shorelines to occupy similar positions on multiple occasions. This, in conjunction with a relatively humid climate and a well-vegetated landscape, enabled deflated sediment from beaches to form dunes which stacked upon each other to form an extensive and complex vertical accretionary sequence. Repeated erosion and recycling of pre-existing barriers as well as barrier construction on what is currently the off-shore platform during still-stands in sea-level regressional cycles, when sea levels dropped below ca ?50 m from the present day, has added to the complexity of the preserved terrestrial barrier record. The Wilderness barrier system contrasts with barriers developed elsewhere in the world where higher rates of crustal uplift have allowed preservation of a more complete and more widely spaced palaeorecord. This research also shows the utility of integrating off-shore topography as revealed by bathymetry, with terrestrial topographic data for the better understanding of the evolution of palaeo-coastlines and the preserved dune record found on present-day coastal plains. Local variation in the topography of the continental shelf at Wilderness has generated spatial and temporal complexity within the sedimentary records of individual barriers as well as having a significant influence on preservation.  相似文献   

Probabilistic evaluation of soil–foundation–structure interaction effects on seismic structural response     

Masoud Moghaddasi  Misko Cubrinovski  J. Geoff Chase  Stefano Pampanin  Athol Carr 《地震工程与结构动力学》2011,40(2):135-154

Complex seismic behaviour of soil–foundation–structure (SFS) systems together with uncertainties in system parameters and variability in earthquake ground motions result in a significant debate over the effects of soil–foundation–structure interaction (SFSI) on structural response. The aim of this study is to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. An established rheological soil‐shallow foundation–structure model with equivalent linear soil behaviour and nonlinear behaviour of the superstructure has been used. A large number of models incorporating wide range of soil, foundation and structural parameters were generated using a robust Monte‐Carlo simulation. In total, 4.08 million time‐history analyses were performed over the adopted models using an ensemble of 40 earthquake ground motions as seismic input. The results of the analyses are used to rigorously quantify the effects of foundation flexibility on the structural distortion and total displacement of the superstructure through comparisons between the responses of SFS models and corresponding fixed‐base (FB) models. The effects of predominant period of the FB system, linear vs nonlinear modelling of the superstructure, type of nonlinear model used and key system parameters are quantified in terms of different probability levels for SFSI effects to cause an increase in the structural response and the level of amplification of the response in such cases. The results clearly illustrate the risk of underestimating the structural response associated with simplified approaches in which SFSI and nonlinear effects are ignored. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Lead isotope systematics of ore systems of the Macquarie Arc — Implications for arc substrate     

David B. Forster  Graham R. Carr  Peter M. Downes 《Gondwana Research》2011,19(3):686-705

The Macquarie Arc of New South Wales hosts several major Au and Cu deposits. We present new Pb isotope results for Cadia, the Copper Hill, Little Copper Hill and Cowal deposits, along with data from the CSIRO database. The results generally plot close to established mantle growth curves and are similar to oceanic basalts. Data for individual deposits mostly have Pb model ages consistent with independent age constraints on mineralization. Intrusions associated with the Early Silurian mineralization at Cadia and Goonumbla have narrow and distinct Pb isotope signatures that we interpret to be the result of partial melting of already LILE-enriched mantle-like sources. The data suggest that deposits of the Macquarie Arc derived Pb from one or more long-lived mantle-like Pb isotope reservoirs without significant contributions of crustal Pb prior to the Benambran Orogeny.Data for the Copper Hill deposits includes unradiogenic, possibly old Pb and supports previous workers who suggested that old MORB-like basalts may occur at depth in the area. The Peak Hill deposit has the most unradiogenic signature and has the lowest ²⁰⁸Pb/²⁰⁴Pb and ²⁰⁷Pb/²⁰⁴Pb. These signatures closely match Cambrian MORB-like basalts in the Koonenberry Belt and are unlike Cambrian mafic rocks in Victoria. Similar rocks could form part of the substrate to other parts of the Macquarie Arc.  相似文献   

Gender-specific out-migration, deforestation and urbanization in the Ecuadorian Amazon   总被引：4，自引：0，他引：4  

Alisson F. Barbieri  David L. Carr 《Global and Planetary Change》2005,47(2-4):99

The Ecuadorian Amazon, one of the richest reserves of biodiversity in the world, has faced one of the highest rates of deforestation of any Amazonian nation. Most of this forest elimination has been caused by agricultural colonization that followed the discovery of oil fields in 1967. Since the 1990s, an increasing process of urbanization has also engendered new patterns of population mobility within the Amazon, along with traditional ways by which rural settlers make their living. However, while very significant in its effects on deforestation, urbanization and regional development, population mobility within the Amazon has hardly been studied at all, as well as the distinct migration patterns between men and women. This paper uses a longitudinal dataset of 250 farm households in the Northern Ecuadorian Amazon to understand differentials between men and women migrants to urban and rural destinations and between men and women non-migrants. First, we use hazard analysis based on the Kaplan–Meier (KM) estimator to obtain the cumulative probability that an individual living in the study area in 1990 or at time t, will out-migrated at some time, t+n, before 1999. Results indicate that out-migration to other rural areas in the Amazon, especially pristine areas is considerably greater than out-migration to the growing, but still incipient, Amazonian urban areas. Furthermore, men are more likely to out-migrate to rural areas than women, while the reverse occurs for urban areas. Difference-of-means tests were employed to examine potential factors accounting for differentials between male and female out-migration to urban and rural areas. Among the key results, relative to men younger women are more likely to out-migrate to urban areas; more difficult access from farms to towns and roads constrains women's migration; and access to new lands in the Amazon–an important cause of further deforestation–is more associated with male out-migration. Economic factors such as engagement in on-farm work, increasing resource scarcity–measured by higher population density at the farm and reduction in farm land on forest and crops–and increase in pasture land are more associated with male out-migration to rural areas. On the other hand, increasing resource scarcity, higher population density and weaker migration networks are more associated with female out-migration to urban areas. Thus, a “vicious cycle” is created: Pressure over land leads to deforestation in most or all farm forest areas and reduces the possibilities for further agricultural extensification (deforestation); out-migration, especially male out-migration, occurs to other rural or forest areas in the Amazon (with women being more likely to choose urban destinations); and, giving continuing population growth and pressures in the new settled areas, new pressures promote further out-migration to rural destinations and unabated deforestation.  相似文献   

Classical novae from the POINT–AGAPE microlensing survey of M31 – II. Rate and statistical characteristics of the nova population     

M. J. Darnley †  M. F. Bode  E. Kerins  A. M. Newsam  J. An  P. Baillon  V. Belokurov  S. Calchi Novati  B. J. Carr  M. Crézé  N. W. Evans  Y. Giraud-Héraud  A. Gould  P. Hewett  Ph. Jetzer  J. Kaplan  S. Paulin-Henriksson  S. J. Smartt  Y. Tsapras  M. Weston 《Monthly notices of the Royal Astronomical Society》2006,369(1):257-271

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The effect of an offshore bank in attenuating waves     

M.J. Tucker  A.P. Carr  E.G. Pitt 《Coastal Engineering》1984,8(1):96

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Recognition and palaeoclimatic implications of late Quaternary niche glaciation in eastern Lesotho     

Stephanie C. Mills  Stefan W. Grab  Simon J. Carr 《第四纪科学杂志》2009,24(7):647-663

Geomorphic evidence of former glaciation in the high Drakensberg of southern Africa has proven controversial, with conflicting glacial and non‐glacial interpretations suggested for many landforms. This paper presents new geomorphological, sedimentological and micromorphological data, and glacier mass‐balance modelling for a site in the Leqooa Valley, eastern Lesotho, preserving what are considered to be moraines of a former niche glacier that existed during the Last Glacial Maximum (LGM). The geomorphology and macro‐sedimentology of the deposits display characteristics of both active and passive transport by glacial processes. However, micromorphological analyses indicate a more complex history of glacial deposition and subsequent reworking by mass movement processes. The application of a glacier reconstruction technique to determine whether this site could have supported a glacier indicates a reconstructed glacier equilibrium line altitude (ELA) of 3136 m a.s.l. and palaeoglacier mass balance characteristics comparable with modern analogues, reflecting viable, if marginal glaciation. Radiocarbon dates obtained from organic sediment within the moraines indicate that these are of LGM age. The reconstructed palaeoclimatic conditions during the LGM suggest that snow accumulation in the Drakensberg was significantly higher than considered by other studies, and has substantial relevance for tuning regional climate models for southern Africa during the last glacial cycle. Copyright © 2009 John Wiley & Sons, Ltd.  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