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61.
Seven samples from the Limestone and Boulder Conglomerate Members of the Bulltinden Formation have yielded poorly preserved conodonts. On tentative identifications Periodon aculeatus Hadding and Prioniodus cf. P. alobatus Bergstrom at the base of the formation suggest an Ordovician lower Caradoc, or older age. This confirms that the Vcstgotabrcen Formation unconformably beneath underwent high-pressure mctamorphism during the Taconic and/or Finmarkian phases of the Caledonian orogeny. The conodonts show affinity to the North Atlantic Province suggesting a deeper water marine depositional environment. Conodont colour alteration indices of five indicate that the Bulltinden Formation was heated to temperatures in excess of 300°C, probably during the middle-upper Silurian main Caledonian uplift event. 相似文献
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HANS BECKER 《地质学报》1937,(Z1)
During the last year I had ample opportunity for geologicalexcursions in the surroundings of Nanking,both with the students of theDepartment of Geology of National Central University,and in connectionwith fieldwork for the Geological Research Institute of the AcademiaSinica.From casual observations on these trips,I came to some 相似文献
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66.
Stability Relations of the Ferruginous Biotite, Annite 总被引:12,自引:0,他引:12
Annite, KFe3AISi3O10(OH)2 a member of the iron biotites andthe ferrous analogue of phlogopite, has been synthesized andits phase relations have been determined as functions of temperature,fugacity of oxygen (fo2), and total pressure (PtotalPH2O+PH2).A method for controlling fo2at high total pressures is described,and data for the oxygen buffers used are given.Buffers range from quartz+iron+fayalite assemblages (low fo2)to magnetite-hematite assemblages (high fo2). Optical propertiesand unit-cell dimensions of synthetic annites depend on theconditions of synthesis. By recalculating published analyses of natural iron-rich biotitesit can be shown that one cannot assume a constant hydrogen contentfor such biotites. Oxidation may have occurred by drying at115?C. Octahedral occupancy therefore cannot be calculated fromsuch data. Phase relations of annite are presented in 2,070 and 1,035 barsections. Depending on fo2-T values annite was found to decomposeto one of the following assemblages: hematite+ sanidine, magnetite+sanidine,fayalite+leucite+kalsilite, iron+sanidine. All decompositionsare dehydration and redox reactions and are sensitive to changesin fH20 and fo2 (or fH20 and fH2). At 2, 070 bars total pressureannite+magnetite+sanidine can coexist between 425?C and 825?C, depending upon the magnitude of fo2. In the presence of quartz the stability field of annite is morerestricted. Phase equilibria in the system KAlSiO4SiO2FeO2H2have been summarized schematically. Wherever possible, thermodynamic extrapolations are made totest the internal consistency of the data. Enthalpies of formationare calculated for both annite and phlogopite. Ranges of fo2values in nature as well as mechanisms for changes in fo2 areinvestigated. It is useful to distinguish between assemblageswhich are internally buffered with respect to fo2changes andthose which are not buffered. The applications of individualreactions involving annite to specific geologic problems arediscussed with respect to igneous, metamorphic, and sedimentaryrocks. 相似文献
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ATLE NESJE HANS PETTER SEJRUP 《Boreas: An International Journal of Quaternary Research》1988,17(3):371-384
A considerable discussion concerning the extent of the last Scandinavian and Scottish ice sheets has continued for several years. In contrast to earlier models based on an ice sheet extending to the edge of the continental shelf, recent proposals favor a limited geographical and vertical extent and imply that the Scandinavian and British ice sheets did not coalesce in the North Sea. These models indicate an ice-free, open embayment in the northern North Sea and areas of dry land in the southern North Sea region during the Late Weichselian/Devensian glacial maximum. Late Weichselian ice-sheet profiles from the North Sea to the adjacent land areas of southern Norway have been tentatively reconstructed. Low-gradient profiles in the present shelf areas are explained by unconsolidated, deformable sediments on the continental shelf inducing subglacial water pressure and low basal shear stress beneath marginal parts of the Scandinavian ice sheet. Combined with higher basal shear stress conditions in the present mainland areas, this explains the slightly concave and convex shape of the reconstructed ice-sheet profiles in the present coastal and inland areas of western Norway, respectively. 相似文献
69.
HANS SOLERøD 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):7-12
Solerød, Hans: Geografi som universitetsfag, faglig sammensetning og organisasjon. Geografisk Tidsskrift 83: 7–12. Copenhagen, June 1, 1983. Geograhy as a science in Norway: Research and University training as well as the application of geography in the community. 1982. 相似文献
70.
ATLE NYGÅRD HANS PETTER SEJRUP HAFLIDI HAFLIDASON MARCELLO CECCHI DAG OTTESEN 《Boreas: An International Journal of Quaternary Research》2004,33(1):1-17
Analysis of 2D and 3D seismic records from the continental shelf off western Norway, in combination with chronological constraints from 14 C dates, has led to a model for the glacial development in these shelf areas between c. 15 and 13 14 C ka BP. On the shallow Måløy Plateau adjacent to the Norwegian Channel, iceberg scours are preserved below a prominent moraine ridge, which by correlation to the Norwegian Channel indicate ice retreat at c. 15 14 C ka BP. Subsequently, the ice advanced across the scoured surface and deposited a till sheet before stabilizing to deposit a prominent moraine, termed the Bremanger Moraine. Based on location on the shelf, seismic stratigraphy, morphology and C dates the Bremanger Moraine is correlated with a significant moraine on the continental shelf off Trøndelag. We suggest that these features are products of a regional glacial event, the Bremanger Event, dated to <15–13.3 14 C ka BP. The Bremanger Event is probably a result of the deteriorating climatic conditions in the NE Atlantic during Heinrich event 1. 相似文献