Statistical prediction of tropical cyclone motion in the northwest of Australia     

Dr. Tom J. Lyons  C. C. Joyce 《Theoretical and Applied Climatology》1983,32(2-3):201-218

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The Cretaceous-Tertiary fireball layer,ejecta layer and coal seam: Platinum-group element content and mineralogy of size fractions     

Noreen Joyce Evans  D. Conrad Gregoire  Wayne D. Goodfellow  Norman Miles  Jn Veizer 《Meteoritics & planetary science》1994,29(2):223-235

Abstract— Grain size separates of the Cretaceous-Tertiary (K-T) fireball layer at marine sites and the entire K-T boundary interval at nonmarine sites (fireball layer, ejecta layer, coal seam) were analysed for platinum-group elements (PGE: Ru, Ir, Ft, Pd, Rh) and Au using inductively coupled plasma mass-spectrometry. X-ray diffractometry and scanning electron microscopy were performed on each fraction to establish the mineralogy. It was determined that the most abundant minerals in the finest fraction were a smectite-group mineral at marine K-T sites and illite-smectite mixed layer clay at nonmarine K-T sites. Positive correlation of PGE content and mineralogy indicates that the PGE are presently associated with these clay minerals which were likely formed by alteration of a condensed mafic phase (e.g., olivine or pyroxene). The correlation of clay mineral abundance with PGE content is imperfect because not all of the clay minerals in the fireball layer are derived by alteration of the original condensed ejecta. In addition, undetected PGE host(s), present in trace amounts, are likely also present.  相似文献   

Non-synchronous response of adjacent floodplain systems to Holocene environmental change     

Mark P. Taylor  John Lewin 《Geomorphology》1997,18(3-4)

Two adjacent upland floodplains are compared to establish the local response of floodplains to environmental change. Radiocarbon dating, the analysis of sedimentary exposures, terrace mapping, aerial photography and archaeological evidence are used to examine Late Quaternary valley fill sediments on the Afon Tanat and the Afon Vymwy in the Upper Severn Basin, Wales, UK.The alluvial stratigraphy of the two floodplain systems consists of Late Devensian (last glacial) fluvio-glacial sediments at the valley margins deposited under a braided outwash river regime. Holocene age terraces, with floodplain and palaeochannel deposits composed of gravels overlain by silty-sands, are inset into this older unit and were formed by meandering fluvial channel systems. A combination of field and laboratory data demonstrates that from the mid-late Holocene the two floodplain systems had divergent development. The Afon Vyrnwy has remained vertically stable for the last ca. 4000 yrs. whereas the adjacent Afon Tanat continued to be vertically and laterally active.Both floodplain systems have been affected by Late Quaternary climatic fluctuations and anthropogenic activity from the Bronze Age to the Roman period, but local geomorphic gradient controls, combined with a possibly greater focus of anthropogenic activity in the Tanat catchment, may explain the differential evolution of the two systems. The data demonstrate that multiple reach-scale studies are essential for revealing significant stages in the chronology and historical development of fluvial systems.  相似文献   

The West Victorian Uplands of Southeastern Australia: Origin and history     

E. B. Joyce 《地球表面变化过程与地形》1992,17(4):407-418

The West Victorian Uplands is a region of low relief, gentle gradients, young volcanicity and local domal uplift. These characteristics distinguish it from the rest of the Eastern Highlands of Australia. The origin of the West Victorian Uplands dates back to uplift in the Cretaceous, but elevation and relief have always remained low. Further uplift, extending westwards from central Victoria, may have begun raising the West Victorian Uplands in Middle Tertiary times. Doming, fault activity, earthquakes and volcanism are extending progressively westwards. Not only may the Eastern Highlands of Victoria have grown in this way in the past, but the area may also provide a view of the early evolution of the Eastern Highlands of Australia.  相似文献   

Climatic and halokinetic controls on alluvial–lacustrine sedimentation during compressional deformation,Andean forearc,northern Chile          下载免费PDF全文

Laura A. Evenstar  Adrian J. Hartley  Stuart G. Archer  Joyce E. Neilson 《Basin Research》2016,28(5):634-657

The Salar de Atacama forms one of a series of forearc basins developed along the western flank of the Central Andes. Exposed along the northwest margin of the basin, a salt‐cored range, the Cordillera de la Sal, records the Mid‐Miocene to recent sedimentological and structural development of this basin. Sediments of the Mid‐Miocene Vilama Formation record the complex interaction between regional/local climate change, halokinesis and compressional deformation. This study reveals how these factors have controlled the facies development and distribution within the Salar de Atacama. Detailed sedimentary logging, cross‐sections and present day geomorphology through the northern Cordillera de la Sal have been used to establish a lithostratigraphy, chronostratigraphy and the regional distribution of the Vilama Formation. The Vilama Formation documents an increase in aridity with a hiatus in sedimentation from Mid‐Miocene to 9 Ma with initial uplift of the Cordillera de la Sal. From 9 Ma to 8.5 Ma deposition of a meandering fluvial system is recorded followed by a rapid decrease in sedimentation till 6 Ma. From 6 to 2 Ma, the deposition of extensive palustrine carbonates and distal alluvial–mudflat–lacustrine demonstrates the existence of an extensive lake within the Salar de Atacama. Post 2 Ma, the lake decreased in size and braided alluvial gravels associated with alluvial fans were widespread through the region suggesting a final shift to hyperarid conditions. By comparing the Vilama Formation with similar age facies throughout northern Chile and southern Peru, several shifts in climate are recognized. Climate signatures within northern Chile appear to be largely diachronous with the last regional event in the Mid‐Miocene. Since that time, humid events have been restricted to either Precordillerian basins or the Central Atacama. Within the Central Atacama, the final switch to hyperarid conditions was not till the earliest Pleistocene, much later than previously estimated within the region.  相似文献   

Infrared observations of the surface and atmosphere of Titan     

R.F. Knacke  T. Owen  R.R. Joyce 《Icarus》1975,24(4):460-464

Infrared photometry of Titan, Saturn, and Saturn's Rings at 3.5, 4.9, 17.8, and 18.4 μm is reported. Comparison of the albedo of Titan in the 4.9 μm “window” with the albedo of the rings and with laboratory spectra suggests that frost, possibly water ice, could be a major constituent. If thick clouds are present they must be very dark at 4.9 μm. The 17.8 and 18.4 μm data are not consistent with a clear, dense molecular hydrogen atmosphere.  相似文献   

Application of cluster analysis to detection of subtle variation in a granitic intrusion     

A.S. Joyce 《Chemical Geology》1973,11(4):297-306

An apparently homogeneous adamellite intrusion with an outcrop area of 655 km² within the composite Murrumbidgee Batholith, Australian Capital Territory, has been subjected to cluster analysis using 25 samples analysed for 32 chemical constituents. Despite the fact that conventional mapping techniques failed to demonstrate any internal compositional variation, cluster analysis distinguished two main groups and two subordinate groups of samples which are geographically meaningful and which show minor differences in texture and in the triclinicity of their potassium feldspars. This is taken to imply that the intrusion is composite.  相似文献   

A Benthic Terrain Classification Scheme for American Samoa   总被引：2，自引：0，他引：2  

Emily R. Lundblad  Dawn J. Wright  Joyce Miller  Emily M. Larkin  Ronald Rinehart  David F. Naar  Brian T. Donahue  S. Miles Anderson  Tim Battista 《Marine Geodesy》2006,29(2):89-111

Coral reef ecosystems, the most varied on earth, continually face destruction from anthropogenic and natural threats. The U.S. Coral Reef Task Force seeks to characterize and map priority coral reef ecosystems in the U.S./Trust Territories by 2009. Building upon NOAA Biogeography shallow-water classifications based on Ikonos imagery, presented here are new methods, based on acoustic data, for classifying benthic terrain below 30 m, around Tutuila, American Samoa. The result is a new classification scheme for American Samoa that extends and improves the NOAA Biogeography scheme, which, although developed for Pacific island nations and territories, is only applicable to a maximum depth of 30 m, due to the limitations of satellite imagery. The scheme may be suitable for developing habitat maps pinpointing high biodiversity around coral reefs throughout the western Pacific.  相似文献   

Biotic variation in coastal water bodies in Sussex, England: Implications for saline lagoons     

Chris B. Joyce  Cristina Vina-Herbon  Daniel J. Metcalfe 《Estuarine, Coastal and Shelf Science》2005,65(4):633-644

Coastal water bodies are a heterogeneous resource typified by high spatial and temporal variability and threatened by anthropogenic impacts. This includes saline lagoons, which support a specialist biota and are a priority habitat for nature conservation. This paper describes the biotic variation in coastal water bodies in Sussex, England, in order to characterise the distinctiveness of the saline lagoon community and elucidate environmental factors that determine its distribution. Twenty-eight coastal water bodies were surveyed for their aquatic flora and invertebrate fauna and a suite of exploratory environmental variables compiled. Ordination and cluster analyses were used to examine patterns in community composition and relate these to environmental parameters. Biotic variation in the coastal water body resource was high. Salinity was the main environmental parameter explaining the regional distribution of taxa; freshwater and saline assemblages were evident and related to sea water ingress. Freshwater sites were indicated by the plant Myriophyllum spicatum and gastropod mollusc Lymnaea peregra, while more saline communities supported marine and brackish water taxa, notably a range of chlorophytic algae and the bivalve mollusc Cerastoderma glaucum. Site community differences were also related to bank slope and parameters describing habitat heterogeneity. A saline lagoon community was discerned within the matrix of biotic variation consisting of specialist lagoonal species with associated typically euryhaline taxa. For fauna, the latter were the molluscs Abra tenuis and Hydrobia ulvae, and the crustaceans Corophium volutator and Palaemonetes varians, and for flora they were the algae Ulva lactuca, Chaetomorpha mediterranea, Cladophora spp. and Enteromorpha intestinalis. One non-native polychaete species, Ficopomatus enigmaticus, also strongly influenced community structure within the lagoonal resource. The community was not well defined as specialist and associated taxa were distributed throughout the spectrum of sites surveyed. Implications for the identification and conservation of saline lagoons are discussed.  相似文献   

Towards quantitative control on discreteness error in the non-linear regime of cosmological N-body simulations     

M. Joyce  B. Marcos  T. Baertschiger 《Monthly notices of the Royal Astronomical Society》2009,394(2):751-773

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