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LOTTE SELSING 《Boreas: An International Journal of Quaternary Research》1981,10(3):275-279
The Brorfelde hills in northwestern Sjælland are built up of thick fluvioglacial deposits covered by basal till. A stress analysis of syn- and postdepositional normal faults in these sediments indicates that the faults are a result of buried dead ice. The hills can be classified as autochthonous ice-sustained kame or crevasse deposits which have been transgressed by a later ice advance 相似文献
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Clinopyroxenes and Coexisting Mafic Minerals from the Alkaline Ilimaussaq Intrusion, South Greenland 总被引：2，自引：1，他引：2
The Ilímaussaq intrusion consists of an augite syeniteshell and a central cumulitic series of layered peralkaline(agpaitic) nepheline syenites with both roof and bottom cumulates.Microprobe analyses of the strongly zoned mafics show that thepyroxenes range from ferro-salite through hedenbergite to aegirine,the amphiboles from hastingsite through katophorite to arfvedsonite,and the olivines from Fo16.8 to FO0.2. Aenigmatite analysesare also presented. The crystal chemistry of the pyroxenes isdiscussed in detail. The behaviour of the various elements isdiscussed in relation to the conditions in the coexisting magma.The relation between oxygen fugacity and silica activity andthe stability of fayalite and Na-poor pyroxenes in over-andundersaturated magmas is considered. The persistent stabilityof these minerals in the strongly undersaturated Ilimaussaqmagma shows that the oxygen fugacities in Ilímaussaqwere lower than in any other known alkaline suites. Based onthe compositional development in the mafic minerals it is inferredthat the intrusion formed from at least three separate pulsesof successively more differentiated magma: (1) an augite syenitemagma congealed inwards from the sides, (2) a peralkaline undersaturatedmagma gave rise to the roof cumulates which congealed successivelydownwards. The differentiating magma was water-undersaturatedand underwent depletion in Mg and enrichment in Zr and Na. Thecontemporaneous bottom cumulates are hidden beneath the nowvisible bottom cumulates which possess a still more differentiatedliquidus mineral assemblage and are ascribed to a third separatemagma pulse. 相似文献
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LOTTE SELSING VAGN MEJDAHL 《Boreas: An International Journal of Quaternary Research》1994,23(1):92-104
Thermoluminescence age determinations were performed on four aeolian sand samples of late Holocene scenceagesediments from Stavanger airport, Sola, in southwest Norway. The locality is well suited for testing thermoluminescence dating because of a good agreement between radiocarbon ages and age information based on archaeological typology and sea level changes. The conclusion from a comparison of thermoluminescence and archaeologicaltypologyradiocarbon dates is that it is possible to date well bleached sediments as young as 1600 years with thermoluminescence (TL). The TL dates for the aeolian deposits are in accord with expected ages. Six formal, diachronous aeolian/non-aeolian phases are defined and grouped together as the Sola Episode. The first phase onousaeolian/non-aeolianof aeolian activity was short-lasting and took place in the middle Subboreal chronozone. A second and lianactivitywaslong-lasting period, dominated by aeolian activity, took place from the transition between the Subboreal and Subatlantic chronozones until the present. We conclude that human activities were the releasing factor for the aeolian activity recorded in sand sheets. 相似文献
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LARSEN LOTTE M.; PEDERSEN ASGER K.; SUNDVOLL BJORN; FREI ROBERT 《Journal of Petrology》2003,44(1):3-38
Alkaline picrites and basalts constitute 20–200 m of lavaflows and hyaloclastites in the middle part of an 相似文献
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Processes in High-Mg, High-T Magmas: Evidence from Olivine, Chromite and Glass in Palaeogene Picrites from West Greenland 总被引：15，自引：1，他引：14
Uncontaminated volcanic rocks from the 60 Ma Vaigat Formation,West Greenland, contain 6·5–30 wt % MgO, averaging15·5 wt % MgO. Olivine (mg-number 77·4–93·3)forms diverse assemblages of zoned phenocrysts and xenocrystsshowing evidence for equilibrium and fractional crystallization,oxidation, partial to complete re-equilibration, as well asmagma mixing. The olivine crystals contain glass inclusionsand have high contents of Ca and Cr, indicating that all olivineswith up to mg-number 93·0 crystallized from melts. Associatedchromites (mg-number 45·4–77·2) are essentiallyunzoned and in equilibrium with the olivines. Matrix glassesfrom pillow breccias have 6·7–8·8 wt % MgOand quenched close to 1200°C with oxidation states one log-unitabove the NNO (nickel–nickel oxide) buffer. Compositionaldifferences between the glasses from different volcanic membersare inherited from the primary melts. The magmas erupted ascrystal-charged melts, and liquids with more than 相似文献
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