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191.
Studies of interactions among bioactive compounds are often difficult to interpret unambiguously.A priori assumptions about the nature of such interactions can seriously distort analysis of the data.Byapplying a rank order analysis appropriate to the naturally ordinal scale of response to xenobiotic insult,several co-herbicides were successfully identified from among numerous candidates in an experimentinvolving multiple blocks,rates and species.Moreover,underlying herbicide interactions weresubstantiated and identified which were not apparent by more traditional parametric analysis. 相似文献
192.
The lead and fluorspar mining area of the Peak District, otherwise known as the South Pennine Orefield, includes much of Derbyshire and a small part of Staffordshire. There are some 2000 named mineral veins and related strata-bound deposits, containing galena, sphalerite, fluorite, baryte and calcite, hosted in Lower Carboniferous (Dinantian) limestones and dolomites. Small amounts of pyrite and chalcopyrite, and traces of many other minerals and hydrocarbons, are also present. Here we offer an explanation of how the minerals of the South Pennine Orefield were emplaced within the host rock. 相似文献
193.
DAVID E. SUGDEN 《Boreas: An International Journal of Quaternary Research》1988,17(3):300-300
Book reviewed in this article:
Van der Veen, C. J. & Oerlemans, J. (eds.) 1986: Dynamics of the West Antarctic Ice Sheet. 相似文献
Van der Veen, C. J. & Oerlemans, J. (eds.) 1986: Dynamics of the West Antarctic Ice Sheet. 相似文献
194.
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196.
MATTHEW R. BENNETT DAVID HUDDART RICHARD I. WALLER NICHOLAS G. MIDGLEY SILVIA GONZALEZ ALEXANDRE TOMIO 《Boreas: An International Journal of Quaternary Research》2004,33(2):97-107
This paper describes the internal architecture of a push moraine formed by a winter-spring surge of Hagafellsjökull-Eystri (Iceland) in 1998/99. The sedimentary architecture of this push moraine consists of a multilayered slab of glaciofluvial sediments with a monoclinal structure that has been displaced laterally by the advancing ice margin. The crest and ice-distal face of the moraine consist of subhorizontal sediment sheets, while the ice-proximal face dips steeply (45° to 90°) towards the ice margin. The core of the moraine consists of frozen sediment and thin slabs of glacier ice are embedded in its proximal face. The sediment slabs are characterized by both brittle and ductile styles of deformation. We argue that the observed variation in deformation style is dependent on whether the glacial foreland was frozen or unfrozen at the time of displacement. Frozen foreland would behave in a brittle fashion, while unfrozen foreland is likely to have deformed in a more ductile manner. The associated spatial variations in the degree of foreland freezing could be explained by variation in ice-marginal snow cover. We conclude that the thermal regime of the foreland, and the timing of the ice advance, is of importance to the style of internal deformation found within ice-marginal push moraines. 相似文献
197.
DAVID G. CROOT PETER C. SIMS 《Boreas: An International Journal of Quaternary Research》1996,25(1):37-46
Traditional views of glacigenic processes focus on erosion of hard bedrock and deposition of unconsolidated till. In the 1960s and 1970s attention was directed towards the glacier debris cascade, which linked these two end members. A limited understanding of the relationship between bedrock character, the supposed processes of erosion, debris comminution and texture emerged. In the 1980s researchers began to appreciate the important role which glaciotectonism plays in the spectrum of glacigenic processes, although little attention has been paid to the interface between glacial erosion, glaciotectonism and the early stages of the debris cascade system. A coastal section at Fanore, County Clare, Ireland affords a unique opportunity to examine a range of glacial deposits which represent a series in the erosion, tectonism and comminution stages of till genesis. Major elements of the site are bedrock rafts, glaciotectonic breecias, immature till and mature till. In all cases > 98% of the elements comprise Carboniferous limestone. Research at Fanore has focused on textural properties. Analysis of bulk samples of the sediments demonstrates a continuum of textural development from the glaciotectonism of the bedrock (breecia production and bedrock raft comminution) to a homogenized but immature till and to a more mature matrix-dominated deposit. 相似文献
198.
DAVID N. PENNEY 《Boreas: An International Journal of Quaternary Research》1987,16(3):237-247
Ostracoda are probably better indicators of past sea level than has hitherto been realized. This is so because very characteristic low diversity, high productivity faunas occur in the upper reaches of the estuarine environment. Moreover, a fair amount of knowledge exists concerning their ecology. Details are given on the faunas that are present in each estuarine facies, and on how death assemblages can be distinguished from life assemblages. Sea level can be estimated to an accuracy of 50 cm to 100 cm in some NW European microtidal areas, but further research is required on macrotidal coasts to ascertain whether they can be used to pinpoint sea level here. Examples of where Ostracoda have proved of value in sea-level studies are given for North Denmark, The Netherlands, East Ireland, and the Gulf of Gascony. 相似文献
199.
200.
Causes of spatial compositional variations in Mariana arc lavas: Trace element evidence 总被引:3,自引:0,他引:3
New inductively coupled plasma mass spectrometry (ICP-MS) trace element data are presented on a suite of arc lavas from the northern Mariana and southern Bonin island arcs. The samples were dredged from seamounts in the Central Island Province (CIP), the Northern Seamount Province (NSP) and the Volcano Arc (VA), and they range in composition from low-K tholeiites to shoshonites. Previous studies on these samples concluded that the primary compositional control was two-component mixing between a fluid-metasomatized mid-ocean ridge basalt (MORB) source and an enriched, ocean island basalt (OIB)-like, mantle component, with subducted sediment material playing a secondary role. However, the new trace element data suggest that the compositional variations along the Mariana arc can be better explained by the addition of spatially varying subduction components to a spatially varying mantle source. The data suggest that the subduction component in the CIP and VA is dominated by aqueous fluids derived from altered oceanic crust and a pelagic sediment component, while the subduction component in the NSP is dominated by more silicic fluids derived from volcanogenic sediments as well as from pelagic sediment and altered oceanic crust. The mantle wedge in the CIP and VA is depleted relative to a normal mid-ocean ridge basalt source by loss of a small melt fraction, while the mantle wedge in the NSP is enriched either by possible gain of a small melt fraction or addition of a sediment-derived melt. Because the subduction of seamounts controls the arc and back-arc geometries, so the concomitant variation between subducted material and mantle composition may be no coincidence. The high field strength element (HFSE) data indicate a high degree of melting (∼ 25–30%) throughout the arc, ∼ 10% of which may be attributed to decompression and ∼ 20% to fluid addition. 相似文献