排序方式： 共有7条查询结果，搜索用时 0 毫秒
1
1.
2.
3.
4.
SVANTE BJÖRCK JOHN A. DEARING ERS JONSSON 《Boreas: An International Journal of Quaternary Research》1982,11(1):99-111
The magnetic suceptibility of Late Weichselian glacial, late-glacial and post-glacial deposits from Blekinge, southeast Sweden, has been measured. The susceptibility variations proved to be dependent upon the particle size distribution of the sample and the type of bedrock from which the deposit is derived. Comparison of susceptibility variations in the Baltic Ice Lake and lacustrine sediments with biological indicators of environmental change suggests that susceptibility can be a useful complement to studies aimed at identifying lake isolation, climatic change or changes in erosion within the catchment. The results also suggest that comparison of susceptibility versus fraction size curves can aid lithostratigraphic division of unconsolidated deposits. 相似文献
5.
By D. A. HEGG D. S. COVERT H. H. JONSSON R. WOODS 《Tellus. Series B, Chemical and physical meteorology》2009,61(4):669-676
Aerosol samples were collected and cloud condensation nuclei (CCN) concentrations at five supersaturations were measured along and off the central California coast within the cloud-topped, marine boundary layer from aircraft flights during August 2007. Receptor modelling has been applied to estimate the natural versus anthropogenic source contribution of cloud condensation nuclei in this region, a region of climatically important marine stratocumulus. The results suggest that anthropogenic CCN accounted for about 50% of the CCN active at 0.3% supersaturation in this region during the measurement period. 相似文献
6.
7.
Petrology of the Western Reykjanes Peninsula, Iceland 总被引：3，自引：3，他引：3
The active tholeiitic volcanic zone of the Reykjanes Peninsulaconsists of five volcanic fissure swarms, the two westernmostof which are the subject of this petrological study. The recent(less than 12,000 years) extrusives of the swarms group morphologicallyand petrographically into small picrite basalt lava shields,large olivine tholeiite lava shields and tholeiite fissure lavas;formed in that chronological succession. The picrite basalts exhibit a primitive mineralogy with chromite,olivine (Fo 89) and plagioclase (An 90) as phenocrysts and mayrepresent a primary liquid from the mantle. Simultaneous crystallizationof olivine, plagioclase and augite to form glomerocrysts inthe fissure lavas indicate low pressure cotectic crystallizationconditions. Twenty-eight new major element chemical analyses of the lavasare presented. They are generally characterized by a low contentof alkalies and high CaO. The lavas constitute two main suites,a lava shield suite and a fissure lava suite. There is a positivecorrelation between the volume of individual lavas and the contentof incompatible elements of the lavas within each group. Likewisethere is an overall chemical trend through time demonstrated,for example, by a rise in K2O from about 0.02 per cent to 0.24per cent during the last, approximately, 12,000 years. There is an apparent chemical zoning within each volcanic swarmsuch that the most evolved and youngest lavas are found in thecentral axial area of the swarm. This central area is also characterizedby graben subsidence, high magnetic anomalies and high temperaturethermal areas, all indicative of shallow magma reservoir(s).In spite of indications of fractional crystallization in theevolution of the olivine tholeiites and tholeiites, some otherprocesses must be sought to explain the volume chemistry relations.Cyclic volcanic activity is tentatively suggested to explainthe observed regular temporal variations within the swarm, eachcycle starting with the formation of picrite basalts. 相似文献
1