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131.
Adrian M. Lister 《第四纪科学杂志》1993,8(2):95-108
Deer species provide a valuable biostratigraphical tool through Cromer Forest-bed times, due particularly to species turnover between the Early and early Middle Pleistocene. This study is based on the reidentification of 348 fossil antlers. The provenance of most large mammal fossils from the CF-bF, collected over 150 years, was recorded only by the nearest coastal village. None the less, analysis of the cervid taxa by these ‘localities’ reveals interesting patterns. The fauna of the West Runton Freshwater Bed is of early Middle Pleistocene complexion, and that from the foreshore at East Runton is of Early Pleistocene. Pure or nearly pure early Middle Pleistocene assemblages also occur at Kessingland-Pakefield and at Trimingham. At Overstrand, Sidestrand, Mundesley, Bacton and Happisburgh, there is a mixture of Early and early Middle Pleistocene elements. Analysis of Savin's data shows that fossils of earlier species were generally found further down the beach than those of later ones. Late nineteenth century geological surveys, made when bone collecting was at its peak, give additional information about fossil horizons, which in several cases can be related to modern stratigraphical units. Most Early Pleistocene large-mammal bones came from Pastonian conglomerates, in contrast to small-mammal and molluscan assemblages mostly extracted from Pre-Pastonian Crag. However, the diversity of Early Pleistocene CF-bF cervid species in comparison with continental faunas, and their pattern of distribution between sites, suggests they may span more than one chronostratigraphic stage. Early Middle Pleistocene assemblages came from strata now referred to the Cromerian, and the differing proportions of taxa between sites provide limited evidence of time-transgression. 相似文献
132.
Svetlana Kuzmina Adrian M. Lister Mary E. Edwards 《Quaternary Science Reviews》2011,30(17-18):2039-2048
Andrei Sher (1939–2008) was a key individual in Beringian studies who made substantial and original contributions, but also, importantly, built bridges between western and eastern Beringian scientists spanning some five decades of research. He is perhaps best known as a Quaternary palaeontologist, specializing in large mammals, and mammoths in particular, but his field of his scientific research was much broader, encompassing Quaternary geology, stratigraphy, geocryology, and paleoenvironmental reconstructions. He worked mainly in Siberia, in the Kolyma and Indigirka lowlands, and Chukotka, but also completed fieldwork in Alaska and Yukon through joint projects with American and Canadian scientists. Andrei was an active scientist until the last days of his life. He was involved in many different research projects ranging from mammoth evolution, fossil insects and environmental changes and ancient DNA. Without Andrei’s connections between researchers, many unique discoveries would likely be unknown. 相似文献
133.
Paul Jacob Hancock Paul Roberts Michael J. Kesteven Ronald D. Ekers Elaine M. Sadler Tara Murphy Marcella Massardi Roberto Ricci Mark Calabretta Gianfranco de Zotti Philip G. Edwards Jennifer A. Ekers Carole A. Jackson Mark Leach Chris Phillips Robert J. Sault Lister Staveley-Smith Ravi Subrahmanyan Mark A. Walker Warwick E. Wilson 《Experimental Astronomy》2011,32(2):147-177
The Australia Telescope 20 GHz (AT20G) survey is a large area (2?? sr), sensitive (40 mJy), high frequency (20 GHz) survey of the southern sky. The survey was conducted in two parts: an initial fast scanning survey, and a series of more accurate follow-up observations. The follow-up survey catalog has been presented by Murphy et al. (MNRAS 402:2403, 2010). In this paper we discuss the hardware setup and scanning survey strategy as well as the production of the scanning survey catalog. 相似文献
134.
B. Ammann A. F. Lotter U. Eicher M.-J. Gaillard B. Wohlfarth W. Haeberli G. Lister M. Maisch F. Niessen Ch. Schlüchter 《第四纪科学杂志》1994,9(2):119-125
A synthesis is provided of Late-glacial (14-9 ka BP) environmental changes in lowland Switzerland (the ‘Swiss Plateau’). The chronology of deglaciation and subsequent developments in vegetation cover in the area are summarised. The sequence of climatic variations experienced in the region during the Late-glacial is then described and a curve representing the main palaeotemperature variations is presented. 相似文献
135.
We present hornblende, white mica, biotite and alkali feldspar 40Ar/39Ar data from Paleo-Mesoproterozoic rocks of the Mt. Isa Inlier, Australia, which reveal a previously unrecognised post-orogenic, non-linear cooling history of part of the Northern Australian Craton. Plateau and total fusion 40Ar/39Ar ages range between 1500 and 767 Ma and record increases in regional cooling rates of up to 4 °C/Ma during 1440–1390 and 1260–1000 Ma. Forward modelling of the alkali feldspar 40Ar/39Ar Arrhenius parameters reveals subsequent increases in cooling rates during 600–400 Ma. The cooling episodes were driven by both erosional exhumation at average rates of 0.25 km/Ma and thermal relaxation following crustal heating and magmatic events. Early Mesoproterozoic cooling is synchronous with exhumation and shearing in the Arunta Block and Gawler Craton. Late Mesoproterozoic cooling could have either been driven by increased rates of exhumation, or a result of thermal relaxation following a heat pulse that was synchronous with dyke emplacement in the Arunta, Musgrave and Mt. Isa province, as well as Grenville-aged orogenesis in the Albany–Fraser Belt. Latest Neoproterozoic–Cambrian cooling and exhumation was probably driven by the convergence of part of the East Antarctic Shield with the Musgrave Block and Western Australia (Petermann Ranges Orogeny), as well as collisional tectonics that produced the Delamerian–Ross Orogen. Major changes in the stress field and geothermal gradients of the Australian plate that are synchronous with the assembly and break-up of parts of Rodinia and Gondwana resulted in shearing and repeated brittle reactivation of the Mt. Isa Inlier, probably via the displacement of long-lived basement faults within the Northern Australian Craton. 相似文献
136.
A torsional deformation apparatus has been developed which allows the evolution of microstructures and flow patterns in analogue materials to be observed to shear strains in excess of =100 while the loading conditions are kept constant. Using a computer-based video microscopy system the displacement paths of marker particles have been followed in real time, and from these the local strain states in the samples have been calculated. A series of velocity stepping experiments in octachloropropane and norbornene determined the shear localization behaviour displayed by these materials. Both of these materials underwent two phases of localization, a primary localization at the start of an experiment, and a secondary localization following increases in the imposed strain rate. The secondary localization is less pronounced, but is reversible, in the sense that lowering the imposed strain rate widens the zone. An inverse relationship between the fixed imposed strain rate and the width of the zone of localized deformation was established. This velocity dependant localization is ascribed to the softening effect of dynamic recrystallization. 相似文献
137.
The topsoil of around 10 000 km2 in eastern England has recently been sampled intensely at 4609 sites to characterize its geochemistry. The parent materials, which include both solid geology and Quaternary sediments, range in age from Permian to Holocene. The distributions of the concentrations of major and trace elements have been characterized geostatistically, and the role of parent material on their spatial structure (anisotropy) and their spatial relationships (coregionalization) have been investigated. Analysis of variance with the sites grouped by major parent material type showed that this classi?cation accounted for 14 to 48 per cent of the variance for the various elements. Global variograms of 13 elements (Al, As, Ca, Cr, Cu, Fe, Mg, Mo, Ni, P, Pb, Ti, and U) have been computed and modelled. Eleven of the variograms seem to comprise two structures, both of which we modelled with spherical functions, one of short range, 3·5 to 9 km, and the other with a range of 15 to 23 km. The models included a nugget variance, which varied from 27 per cent (for As, Fe, and Mg) to 63 per cent (for P) of the total. The long‐range structures are related to the separations of the major parent materials. The variograms of several elements showed appreciable anisotropy, most notably that of Mg. Anisotropy is evident at short ranges of less than 5 km. This accords with the geological structure of the beds which dip from west to east so that their outcrops are elongated from north to south. A linear model of coregionalization ?tted to the data emphasized several important geochemical associations, which we interpret. Elements commonly associated with clay minerals (Mg, Al) and the clay size fraction (Ti) are dominated by the long‐range structure of the coregionalization, whilst several trace elements (As, Cr, Ni and U) are spatially correlated with Fe over short distances, through adsorption of the former on the surfaces of Fe oxyhydroxides. The topsoil around large urban areas is enriched in lead, but it is not clear whether anthropogenic sources are responsible for this metal's anomalous spatial relationships with other elements. Crown copyright © 2003. Reproduced with the permission of Her Majesty's Stationery Of?ce. Published by John Wiley & Sons, Ltd. 相似文献
138.
The impact of future climate change on sugar beet yields is assessed over western Europe using future (2021–2050) climate scenario data from a General Circulation Model (GCM) and the Broom's Barn simulation model of rain-fed crop growth and yield. GCM output for the 1961–1990 period is first compared with observed climate data and shown to be reliable for regions west of 24° E. Comparisons east of this meridian were less reliable with this GCM (HadCM2) and so were omitted from simulations of crop yield. Climate change is expected to bring yield increases of around 1 t/ha of sugar in northern Europe with decreases of a similar magnitude in northern France, Belgium and west/central Poland, for the period 2021–2050. Averaged for the study area (weighted by current regional production), yields show no overall change due to changed climate. However, this figure masks significant increases in yield potential (due to accelerated growth in warmer springs) and in losses due to drought stress. Drought losses are predicted to approximately double in areas with an existing problem and to become a serious new problem in NE France and Belgium. Overall west and central Europe simulated average drought losses rise from 7% (1961–1990) to 18% (2021–2050). The annual variability of yield (as measured by the coefficient of variation) will increase by half, from 10% to 15% compared to 1961–1990, again with potentially serious consequences for the sugar industry. The importance of crop breeding for drought tolerance is further emphasised. These changes are independent of the 9% yield increase which we estimate, on the basis of work by Demmers-Derks et al. (1998), is the likely direct effect of the increase in atmospheric CO2 concentration by 2021–2050. 相似文献
139.
Catherine Mriaux Amotz Agnon John R. Lister 《Earth and Planetary Science Letters》1998,160(3-4):551-562
We study the thermal structure around a cold deformable lithospheric slab as it sinks to the core–mantle boundary and migrates along it. We present analytical results for the steady thermal structure established by a steady but spatially varying motion. The analysis gives a time-like criterion for the thermal signature of a cold slab to persist by the time that the slab moves along the core–mantle boundary. The model is used to assess the feasibility of a purely thermal origin for some of the observed seismic reflectors near the core–mantle boundary. Calculations of the time-like criterion show that the dynamical conditions in our model, namely the velocity and the thickness of the descending slab, are hard to reconcile with observations of subduction and seismic features. Seismic reflections and refractions from anomalously fast regions above the core–mantle boundary could be explained as thermal slabs if the thickness of the slab at subduction was larger than 200 km or somewhat less if the slab did not split at the core–mantle boundary. A simple thermal model also predicts from mineral physics a certain correlation between S- and P-wave velocity anomalies, which is not observed. However, a purely thermal origin cannot be ruled out if the slab is buckling. This process could be in agreement with the observations: the amplitude of the seismic anomalies, the vertical extent of high-gradient zones and the P versus S comparisons. Chemical heterogeneities and phase transformations remain alternative or complementary explanations. 相似文献
140.
Kathleen L. McInnes Graeme D. Hubbert Debbie J. Abbs Steve E. Oliver 《Meteorology and Atmospheric Physics》2002,80(1-4):217-233
Summary A coastal ocean model capable of modelling tides, storm surge and the overland flow of floodwaters has been further developed
to include the flux of water from tributaries and the forcing from wave breaking that leads to wave setup in the nearshore
zone. The model is set up over the Gold Coast Broadwater on the east coast of Australia. This complex region features a coastal
lagoon into which five tributaries flow and is subject to flooding from extreme oceanic conditions such as storm surge and
wave setup as well as terrestrial runoff. Weather conditions responsible for storm surge, waves and flooding include cyclones
of both tropical and mid-latitude origin.
Two events are modelled. The first is an east coast low event that occurred in April 1989. This event verified well against
available observations and analysis of the model simulations revealed that wave setup produced a greater contribution to the
elevated water levels than the storm surge. The second case to be modelled was tropical cyclone Wanda, responsible for the
1974 floods. Modelled water levels in the Broadwater were reasonably well captured. Sensitivity experiments showed that storm
surge and wave setup were only minor contributors to the elevated sea levels and their contribution was confined to the earlier
stage of the event before the runoff reached its peak. The contribution due solely to runoff exhibited a tidal-like oscillation
that was 180° out-of-phase with the tide and this was attributed to the greater hydraulic resistance that occurs at high tide.
A simulation of this event with present day bathymetry at the Seaway produced sea levels that were 0.3–0.4 m lower than the
simulation with 1974 bathymetry highlighting the effectiveness of deepened Seaway channel to reduce the impact of severe runoff
events in the Broadwater.
Received October 16, 2001 Revised December 28, 2001 相似文献