Study of peristerites using transmission electron microscopy and energy dispersive X-ray analysis     

Arne Olsen 《Contributions to Mineralogy and Petrology》1975,51(4):297-302

Peristerite feldspars from Seiland in Norway have been studied by a combination of transmission electron microscopy and energy dispersive X-ray analysis. The different types of microtextures have been correlated with the local mean composition, and it is found that the miscibility gap between An₄ and An₁₇ extends into the ternary Or—Ab—An region. The orientation of the more common type of exsolution lamellae varies from (08¯1) to about (¯1, 21, ¯2) with increasing potassium content.  相似文献   

Mineralogy and petrology of silicate inclusions in iron meteorites     

T. E. Bunch  Klaus Keil  E. Olsen 《Contributions to Mineralogy and Petrology》1970,25(4):297-340

Silicate inclusions in 17 iron meteorites have been analyzed by the electron microprobe and classified, according to their phase assemblages, compositions, and textures, into three major types: Odessa, Copiapo, and Weekeroo Station, and three miscellaneous types: Enon, Kendall County, and Netschaëvo. Phase compositions in both Odessa- and Copiapo-type inclusions are very similar, but the two types are different in texture and constituent phases. Weekeroo Station-type inclusions are very different in every respect from other inclusions.For Odessa- and Copiapo-type inclusions, the distribution coefficients of Fe²⁺ and Mg in coexisting orthopyroxene and clinopyroxene indicate equilibration temperatures of 1,000° C, and the Ca/(Ca+Mg) ratios indicate temperatures of 900° C to 1,000° C. Equilibration temperatures determined for chromite-olivine pairs have a higher range of 1,154° C to 1,335° C. Minor element distributions among coexisting ferromagnesian silicates in these inclusions follow consistent patterns and are constant for any given sample, suggesting equilibrium assemblages. Major and minor element distributions for Weekeroo Station inclusions are anomalous, indicating nonequilibrium.Compositional data, the fragmentary shapes of many inclusions, the highly differentiated characteristic of two types of inclusions, the apparent disequilibrium between kamacite in inclusions and kamacite of the iron host, and the relict chondrules found in Netschaëvo suggest that many of the inclusions did not form cogenetically with the iron host, but represent pre-existing stony material that was taken up by an iron melt, probably not in the core of the parent body (or bodies).  相似文献   

Core surface flow modelling from high-resolution secular variation     

R. Holme  N. Olsen 《Geophysical Journal International》2006,166(2):518-528

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The electrical conductivity of the mantle beneath Europe derived from C-responses from 3 to 720 hr   总被引：6，自引：0，他引：6  

Nils Olsen 《Geophysical Journal International》1998,133(2):298-308

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Causes of low-frequency ground motion amplification in the Salt Lake Basin: the case of the vertically incident P wave     

Kim B. Olsen  Gerard T. Schuster 《Geophysical Journal International》1995,122(3):1045-1061

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Rapid and rhythmic ice sheet fluctuations in western Scandinavia 15-40 Kya–a review     

Lars Olsen  Harald Sveian  Klaas van der  Borg  Bjørn Bergstram  Maarten Broekmans 《Polar research》2002,21(2):235-242

The onshore record of Middle to Late Weichselian sediments and glacial history in Norway indicates a succession of four major ice advances alternating with rapid, considerable ice recessions and interstadial conditions. During all the glacial advances the ice sheet expanded from onshore/inland positions to the shelf areas. The basis for visualizing these variations in glaciation curves constructed along nine transects from inland to shelf, and for interpretation of the palaeoclimatic history, is the regional Quaternary stratigraphy, more than 300 datings, fossil content and some palaeomagnetic data. The methods applied in recent years for AMS radiocarbon dating of glacial sediments with low organic carbon content have given promising results with respect to accuracy and precision, and the results of such datings were an important tool for our reconstructions and for timing of the ice oscillations. The rapid and rhythmic ice fluctuations, as reconstructed in our new model, have been fairly synchronous in most parts of Norway. Ice advances commenced and culminated at 40, 30-28, 24-21 and 18-15 (¹⁴C) Kya. We describe three intervening interstadials from inland sites: Hattfjelldal I, Hattfjelldal II and Trofors. Our stratigraphical record also includes many indications of high, pre-Holocene, relative sea levels, suggesting a considerable glacioisostatic depression of western Scandinavia during the interstadials. In our glaciation model we suggest that, in addition to precipitation, the mountainous fjord and valley topography, glacial isostasy and relative sea level changes were probably more important for the size of the glacial fluctuations than were air temperature changes.  相似文献   

Holocene sedimentary and environmental development of Aarhus Bay,Denmark – a multi-proxy study     

Peter Rasmussen  George Pantopoulos  Jørn B. Jensen  Jesper Olsen  Hans Røy  Ole Bennike 《Boreas: An International Journal of Quaternary Research》2020,49(1):108-128

Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi-proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X-ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near-shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish-water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea-level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea-level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea-level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years.  相似文献   

CFD modeling of plume and free surface behavior resulting from a sub-sea gas release     

Schalk Cloete  Jan Erik Olsen  Paal Skjetne 《Applied Ocean Research》2009,31(3):220-225

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Cellular energy allocation in the Arctic sea ice amphipod Gammarus wilkitzkii exposed to the water soluble fractions of oil     

Olsen GH  Carroll J  Sva E  Camus L 《Marine environmental research》2008,66(1):213-214

Increasing offshore oil and gas activities in the European Arctic has raised concerns of the potential anthropogenic impact of oil-related compounds on the polar marine ecosystem. We measured cellular energy allocation (CEA) in the sea ice amphipod Gammarus wilkitzkii after exposure for one month to the water soluble fraction (WSF) of oil. The CEA biomarker measures the energy budget of organisms by biochemically assessing changes in carbohydrates, protein and lipid content as well as the electron transport system activity. A significantly higher protein content was observed in the medium dose compared to controls, while the total energy budget was not affected in G. wilkitzkii. This indicates that parts of the energy budget of G. wilkitzkii, which is a key species in the Arctic ecosystem, is affected by a WSF of oil.  相似文献   

VUGS IN ORDINARY CHONDRITES     

Edward Olsen 《Meteoritics & planetary science》1981,16(1):45-59

Large vugs occur in the ordinary chondrite, Farmington. They contain the same phases present in the body of the meteorite, either as vug wall lining or as crystals attached to linings. The morphologies of these phases indicate a history of melting and vapor deposition. These vugs are compared with vugs in the ordinary chondrites, Orvinio and Tadjera, and with published reports of vugs in Rose City and Shaw. It is concluded that although shock events may not cause heating above the liquidus for the body of the meteorite, local pockets of melting and vapor formation do occur due to inhomogenieties in the shock wave pattern. Vugs represent such pockets. Vug formation, as a consequence of shock processing, is widespread among ordinary chondrites and shows no correlation with the average temperature of shock heating, subsequent average cooling rate (as indicated by metallurgical criteria), or blackening of body color.  相似文献