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J. CAMPSIE M. H. RASMUSSEN L. C. KOVACS F. DITTMER J. C. BAILEY N. O. HANSEN J. LAURSEN L. JOHNSON 《Polar research》1990,8(2):237-243
New aeromagnetic data, K-Ar age determinations of dredged marine igneous rocks, as well as other geophysical evidence have shed light on the chronology, nature and evolution of the northern Iceland Plateau. Correspondence between seismic refraction profiles taken on the Jan Mayen Ridge and westward through Jan Mayen Island, suppressed aeromagnetic anomalies, earthquake surface wave studies, and ages of dredged igneous rocks suggest these strata may form an extended region of thickened crust, possibly of Caledonian age, extending westward toward the Kolbeinsey Ridge and northwest to the south wall of the Jan Mayen Fracture Zone. 相似文献
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VALENTIN BURKI LOUISE HANSEN OLA FREDIN THORBJØRN A. ANDERSEN ACHIM A. BEYLICH MICHEL JABOYEDOFF EILIV LARSEN JAN‐FREDERIK TØNNESEN 《Boreas: An International Journal of Quaternary Research》2010,39(3):551-566
Burki, V., Hansen, L., Fredin, O., Andersen, T. A., Beylich, A. A., Jaboyedoff, M., Larsen, E. & Tønnesen, J.‐ F. 2009: Little Ice Age advance and retreat sediment budgets for an outlet glacier in western Norway. Boreas, Vol. 39, pp. 551–566. 10.1111/j.1502‐3885.2009.00133.x. ISSN 0300‐9483 Bødalsbreen is an outlet glacier of the Jostedalsbreen Ice Field in western Norway. Nine moraine ridges formed during and after the maximum extent of the Little Ice Age (LIA). The stratigraphy of proglacial sediments in the Bødalen basin inside the LIA moraines is examined, and corresponding sediment volumes are calculated based on georadar surveys and seismic profiling. The total erosion rates (etot) by the glacier are determined for the periods AD 1650–1930 and AD 1930–2005 as 0.8 ± 0.4 mm/yr and 0.7 ± 0.3 mm/yr, respectively. These rates are based on the total amount of sediment delivered to the glacier margin. The values are almost one order of magnitude higher than total erosion rates previously calculated for Norwegian glaciers. This is explained by the large amount of pre‐existing sediment that was recycled by Bødalsbreen. Thus, the total erosion rate must be considered as a composite of eroded bedrock and of removed pre‐existing sediments. The total erosion rate is likely to vary with time owing to a decreasing volume of easily erodible, unconsolidated sediment and till under the glacier. A slight increase in the subglacial bedrock erosion is expected owing to the gradually increasing bedrock surface area exposed to subglacial erosion. 相似文献
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Abstract Fluid inclusion studies of rocks from the late Archaean amphibolite-facies to granulite-facies transition zone of southern India provide support for the hypothesis that CO2,-rich H2O-poor fluids were a major factor in the origin of the high-grade terrain. Charnockites, closely associated leucogranites and quartzo-feldspathic veins contain vast numbers of large CO2-rich inclusions in planar arrays in quartz and feldspar, whereas amphibole-bearing gray gneisses of essentially the same compositions as adjacent charnockites in mixed-facies quarries contain no large fluid inclusions. Inclusions in the northernmost incipient charnockites, as at Kabbal, Karnataka, occasionally contain about 25 mol. % of immiscible H2O lining cavity walls, whereas inclusions from the charnockite massif terrane farther south do not have visibile H2O Microthermometry of CO2 inclusions shows that miscible CH4 and N2 must be small, probably less than 10mol.%combined. Densities of CO2 increase steadily from north to south across the transitional terrane. Entrapment pressures calculated from the CO2 equation of state range from 5 kbar in the north to 7.5 kbar in the south at the mineralogically inferred average metamorphic temperature of 750°C, in quantitative agreement with mineralogic geobarometry. This agreement leads to the inference that the fluid inclusions were trapped at or near peak metamorphic conditions. Calculations on the stability of the charnockite assemblage biotite-orthopyroxene-K-feldspar-quartz show that an associated fluid phase must have less than 0.35 H2O activity at the inferred P and T conditions, which agrees with the petrographic observations. High TiO2 content of biotite stabilizes it to lower H2O activities, and the steady increase of biotite TiO2 southward in the area suggests progressive decrease of aH2O with increasing grade. Oxygen fugacities calculated from orthopyroxene-magnetite-quartz are considerably higher than the graphite CO2-O2 buffer, which explains the absence of graphite in the charnockites. The present study quantifies the nature of the vapours in the southern India granulite metamorphism. It remains to be determined whether CO2-flushing of the crust can, by itself, create large terranes of largeion lithophile-depleted granulites, or whether removal of H2O-bearing anatectic melts is essential. 相似文献
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The results are given for all the determinations made by the co-operating laboratories of major elements in the six NIMROC rock samples (granite, syenite, lujavrite, norite, pyroxenite and dunite) prepared by the National Institute for Metallurgy in 1966. Relevant statistical data are given for the sets of results for each major constituent, and recommended values for all constituents except Al2 03 , Na2 0, K2 0and CO2 in dunite, Fe2 O3 , MgO and CO2 in the granite, Fe2 3 and CO2 in the norite and CO2 in the pyroxenite.
This report and that on the trace and minor elements issued in 1978 complete the revision of the recommended values. It is suggested that analysts should concentrate rather on those constituents for which the results have shown such a wide scatter that they can be of no usc for reference purposes, than on those for which the ualues are fairly well established. 相似文献
This report and that on the trace and minor elements issued in 1978 complete the revision of the recommended values. It is suggested that analysts should concentrate rather on those constituents for which the results have shown such a wide scatter that they can be of no usc for reference purposes, than on those for which the ualues are fairly well established. 相似文献
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LOUISE A. HANSEN MORTEN E. ØRGENSEN MICHAEL HOUMARK-NIELSEN CHRISTIAN KRONBORG 《Boreas: An International Journal of Quaternary Research》1994,23(4):385-397
Deposits of Late Pleistocene age were investigated near the Fynselv river on the southwestern coast of Jameson Land. East Greenland. The deposits are of fluvial, deltaic shallow marine and glacigenic origin. Four stratigraphic units are recorded. Unit I consists of deltaic and shallow marine deposits reflecting a relative sea level of at least 20 m above the present. Elevated fluvial deposits represent the subaerial part of the depositional system. The system existed during full interglacial and subarctic conditions as indicated by remains or flora and Fauna and unit I is correlated with the Langelandselv interglaciation (isotopic substage 5e). Unit II consists of a till deposited by a glacier in the Scoresby Sund Fjord during the beginning of the Early Weichselian referred to as the Aucellaelv stade. The glacier probably melted in a marine environment. Unit III represents a marine delta system during the Hugin Sø interstade. and reveals a relative sea level of at least 62 m above the present. Unit IV consists of till and kame deposits assumed to be deposited by a glacier in the Scoresby Sund Fjord during the Flakkerhuk stade. probably a Late Weichselian glacier advance. 相似文献
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This paper presents a critical review of previous lichenometric and lichen growth studies in southern parts of West and East Greenland. These studies include classic work from around Søndre Strømfjord, Sukkertoppen, Sermilik and Angmagssalik. Particular emphasis is placed on those studies examining the role played by climatic continentality on the growth rate of crustose lichens in Greenland. The latter part of the paper presents new data on lichen growth rates from Sermilik, between 2001 and 2006, in 22 different lichen species. Measurements show that different species grow at different rates and growth rates vary from site to site. In this study Rhizocarpon geographicum generally grows slowly (<0.2 mm a−1 ) while other species such as Pseudephebe minuscula grow more rapidly (1.0 mm a−1 ) in the same environment. Comparison with other studies shows that taxa-specific growth rates are slightly greater in West than in East Greenland – probably as a result of the slightly more favourable climate and higher precipitation levels. It is suggested that recent climate change, most marked in southern Greenland, will probably result in changed growth curves (over time) for species such as Rhizocarpon geographicum . However, only more precise growth curves and lichenometric dating curves can demonstrate such a phenomenon. 相似文献
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