A paleomagnetic study of the Mull lava succession   总被引：1，自引：0，他引：1  

James M. Hall  R. L. Wilson  Peter Dagley 《Geophysical Journal International》1977,49(2):499-514

Summary. A paleomagnetic study has been made of a succession of 139 non-overlapping basaltic lavas, representing 91 per cent of the longest remaining succession of flows associated with the Paleogene Mull volcano. All the lavas have experienced considerable hydrothermal alteration, probably at up to several million years after initial magnetization and frequently with alteration to the opaque minerals and the production of new potentially magnetic phases. The question of whether directional remagnetization has taken place while preserving within-unit directional consistency and discreteness of unit mean direction is discussed. Extensive directional remagnetization is excluded as an explanation for the data. If stable directions obtained by alternating field remanence cleaning coincide with original TRM directions then a mean pole position for all temporally independent lava directions from the British Tertiary igneous province is at 71.9° N, 167.2° E, with k:22 and α₉₅:3.0°. This pole is significantly different from the geographic pole. If the difference in palaeomagnetic and geographic poles is interpreted in terms of absolute plate motion, then 2010 km of northwards motion of the western part of the Eurasian Plate, at 3.7 cm/yr, has taken place over the last 55 Myr. This motion has implications for the geological history of the Arctic and for the complexity of mantle motions.  相似文献   

IGU working group on applied geography     

Peter H. Nash 《GeoJournal》1983,7(3):313-315

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Provenances of naturalised plants in Australasia     

Peter Holland  Sherry Olson 《The Australian geographer》1989,20(2):136-143

In both Australia and New Zealand, numbers of naturalised flowering plant species have increased steadily since the start of European settlement, and this process shows no sign of abating. Plants native to Western Europe, the Mediterranean basin and the Middle East predominated during the mid‐nineteenth century, but in recent decades other geographical areas (notably the Western Hemisphere, Asia and Southern Africa) have become important sources of adventive plants. Today, the composition of ensembles of naturalised species more closely conforms to the diversity of physical environments in the host area. Species native to mediterranean‐type climates tend to dominate in Victoria, species from the Asian and American tropics are especially significant in Queensland, and species from cool temperate regions compose the bulk of the naturalised flora of south‐western New Zealand.  相似文献   

Multigenetic gravity couple across a modern convergent margin: inheritance from Cretaceous asymmetric extension     

Peter J. J. Kamp  Kerry A. Hegarty 《Geophysical Journal International》1989,96(1):33-41

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Dryland salinity in a subcatchment at Glenthompson,Victoria     

Peter Dixon 《The Australian geographer》1989,20(2):144-152

Dryland salinity is a widespread and serious environmental problem in western Victoria. As a result river environs and farmland have been seriously degraded with loss of habitat, reduced farm production and increased erosion. Until recently, the preferred method of salinity investigation was centred around expensive drilling programs to obtain information on groundwater provinces. More recently, electromagnetic surveys have provided the means of rapidly assessing the levels of soil and water salinities present within the landscape. At a site south of Glenthompson, Victoria, the results of an electromagnetic survey together with an investigation of relevant soil properties are being used to plan salinity control options. High recharge areas do not appear to be present in the study district. The effects of agronomic control options, such as the establishment of perennial grasses, can be predicted by the use of a monthly water balance whereby climatic factors and the crop's efficiency in plant water use can be related. The likely reduction in deep infiltration can then be estimated.  相似文献   

CHILDREN'S PERCEPTION OF A DOWNTOWN SHOPPING CENTER     

Geoffrey C. Smith  Denis J. B. Shaw  Peter R. Huckle 《The Professional geographer》1979,31(2):157-164

This paper offers an exploratory investigation of the effects of a child's age on three behavioral constructs (awareness space, activity space, and attitude) concerning a downtown shopping center in Bristol, England. The data are elicited from three samples of Bristol school children defined according to age and are analyzed using statistical inferential procedures. The results disclose that awareness space and activity space consistently increase with age. In addition, attitudinal responses to specific features of the shopping center exhibit a gradual change over a long-term period.  相似文献   

Magnetic Anomalies, Bathymetry and the Tectonic Evolution of the South Pacific since the Late Cretaceous   总被引：3，自引：0，他引：3  

Peter Molnar  Tanya Atwater  Jacqueline Mammerickx  Stuart M. Smith 《Geophysical Journal International》1975,40(3):383-420

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Climatic deterioration and the end of the Gortian Interglacial in sediments from Derrynadivva and Burren Townland,near Castlebar,County Mayo,Ireland     

Peter Coxon  Gina Hannon  Peter Foss 《第四纪科学杂志》1994,9(1):33-46

Pollen and macrofossil analyses of two sequences of organic sediment in western Ireland have allowed the recognition of the latter parts of the Gortian Interglacial, a Middle Pleistocene temperate stage. The palaeobotanical information from the two sites identifies the preservation of partial sequences from the Gortian Interglacial (believed to be the equivalent of the Hoxnian Stage of Britain and the Holsteinian of Europe). The pollen and macrofossil data from one of the sites, Derrynadivva, span the middle and latter parts of the temperate stage. The results show that fire influenced the vegetation throughout the middle part of the temperate stage, and the termination of the organic depositional sequence appears to have been due to environmental deterioration. The former is identified through the abundant occurrence of charcoal in the sediments, whereas the latter is apparent in the sediment sequence and in the reworking of thermophilous pollen types into the upper part of the deposit. The second site, Burren Townland, records only part of the later zones of the interglacial, but the ericaceous assemblages of the latter part of the Gortian Interglacial are well developed and well preserved. Macrofossil analyses and scanning electron microscopy work on the pollen at the latter site has allowed the recognition of Rhododendron ponticum, adding to previous records of this species, which now has a very disjunct European distribution.  相似文献   

Amino acid diagenesis in the marine bivalve Arctica islandica Linné from northwest European sites: Only time and temperature?     

Hans Petter Sejrup  John-Erik Haugen 《第四纪科学杂志》1994,9(4):301-309

Collections of the molluscan species Arctica islandica from seven sites in Norway, Scotland and the North Sea, ranging in age from recent to Early Pleistocene, have been sampled for amino acid analyses. The shells were sampled in profiles through the valves at different distances from the umbo. In the fossil material a general trend of increasing degree of isoleucine (lle) epimerisation and decreasing amino acid concentrations were found going from the inner part of the valve to the outer. Although less pronounced, there is a similar trend from the central part of the valve to the margin. As the concentration of alloisoleucine (alle) remains nearly constant, the observed changes in alle/lle ratios are a result of variations in the amount of isoleucine. The amino acid composition is fairly uniform in recent shells and the observed gradients are established in mid-Holocene samples. Therefore, it is suggested that the gradients are established during rapid early degradation of the protein, possibly due to microbiological activity. Differences in alle/lle ratios observed in molluscs from sites of the same age and same thermal history could be explained by differences in the exposure to amino-acid-consuming microorganisms during the very early stage of diagenesis.  相似文献   

Mercos — A simple Teflon sampler for ultratrace metal analysis in seawater     

Peter Freimann  Diether Schmidt  Karl Schomaker 《Marine Chemistry》1983,14(1):43-48

This paper describes an uncomplicated sampling technique for ultratrace element analysis of coastal and surface seawaters (maximum depth 100 m). The sampler system is very easy to operate. To prevent contamination problems, interchangeable 500-ml Teflon bottles are used as both sampling and storage vessels. The seawater samples are stabilized in situ by preacidifying the sampling bottles. For the determination of mercury in seawater the desired system has been developed: sampling bottle = storage bottle = reaction vessel.  相似文献