The chronology of a large ice-dammed lake and the Barents–Kara Ice Sheet advances, Northern Russia     

Jan Mangerud  Valery I. Astakhov  Andrew Murray  John Inge Svendsen   《Global and Planetary Change》2001,31(1-4)

Beach and shoreface sediments deposited in the more than 800-km long ice-dammed Lake Komi in northern European Russia have been investigated and dated. The lake flooded the lowland areas between the Barents–Kara Ice Sheet in the north and the continental drainage divide in the south. Shoreline facies have been dated by 18 optical stimulated luminescence (OSL) dates, most of which are closely grouped in the range 80–100 ka, with a mean of 88±3 ka. This implies that that the Barents–Kara Ice Sheet had its Late Pleistocene maximum extension during the Early Weichselian, probably in the cold interval (Rederstall) between the Brørup and Odderade interstadials of western Europe, correlated with marine isotope stage 5b. This is in strong contrast to the Scandinavian and North American ice sheets, which had their maxima in isotope stage 2, about 20 ka. Field and air photo interpretations suggest that Lake Komi was dammed by the ice advance, which formed the Harbei–Harmon–Sopkay Moraines. These has earlier been correlated with the Markhida moraine across the Pechora River Valley and its western extension. However, OSL dates on fluvial sediments below the Markhida moraine have yielded ages as young as 60 ka. This suggests that the Russian mainland was inundated by two major ice sheet advances from the Barents–Kara seas after the last interglacial: one during the Early Weichselian (about 90 ka) that dammed Lake Komi and one during the Middle Weichselian (about 60 ka). Normal fluvial drainage prevailed during the Late Weichselian, when the ice front was located offshore.  相似文献   

Opening of the Fram Strait gateway: A review of plate tectonic constraints   总被引：1，自引：0，他引：1  

  yvind Engen  Jan Inge Faleide  Toril Karlberg Dyreng 《Tectonophysics》2008,450(1-4):51-69

We have revised the regional crustal structure, oceanic age distribution, and conjugate margin segmentation in and around the Lena Trough, the oceanic part of the Fram Strait between the Norwegian–Greenland Sea and the Eurasia Basin (Arctic Ocean). The Lena Trough started to open after Eurasia–Greenland relative plate motions changed from right-lateral shear to oblique divergence at Chron 13 times (33.3 Ma; earliest Oligocene). A new Bouguer gravity map, supported by existing seismic data and aeromagnetic profiles, has been applied to interpret the continent–ocean transition and the influence of Eocene shear structures on the timing of breakup and initial seafloor spreading. Assuming that the onset of deep-water exchange depended on the formation of a narrow, oceanic corridor, the gateway formed during early Miocene times (20–15 Ma). However, if the initial Lena Trough was blocked by terrigenous sediments or was insufficiently subsided to allow for deep-water circulation, the gateway probably formed with the first well developed magnetic seafloor spreading anomaly around Chron 5 times (9.8 Ma; Late Miocene). Paleoceanographic changes at ODP Site 909 (northern Hovgård Ridge) are consistent with both hypotheses of gateway formation. We cannot rule out that a minor gateway formed across stretched continental crust prior to the onset of seafloor spreading in the Lena Trough. The gravity, seismic and magnetic observations question the prevailing hypotheses on the Yermak Plateau and the Morris Jesup Rise as Eocene oceanic plateaus and the Hovgård Ridge as a microcontinent.  相似文献   

Spatial variation in abundance and catch composition of Cancer pagurus in Norwegian waters: biological reasoning and implications for assessment     

Woll  Astrid K.; van der Meeren  Gro I.; Fossen  Inge 《ICES Journal of Marine Science》2006,63(3):421-433

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Crustal structure of the Lofoten–Vesterålen continental margin, off Norway     

Filippos Tsikalas  Olav Eldholm  Jan Inge Faleide   《Tectonophysics》2005,404(3-4):151-174

By compiling wide-angle seismic velocity profiles along the 400-km-long Lofoten–Vesterålen continental margin off Norway, and integrating them with an extensive seismic reflection data set and crustal-scale two-dimensional gravity modelling, we outline the crustal margin structure. The structure is illustrated by across-margin regional transects and by contour maps of depth to Moho, thickness of the crystalline crust, and thickness of the 7+ km/s lower crustal body. The data reveal a normal thickness oceanic crust seaward of anomaly 23 and an increase in thickness towards the continent–ocean boundary associated with breakup magmatism. The southern boundary of the Lofoten–Vesterålen margin, the Bivrost Fracture Zone and its landward prolongation, appears as a major across-margin magmatic and structural crustal feature that governed the evolution of the margin. In particular, a steeply dipping and relatively narrow, 10–40-km-wide, Moho-gradient zone exists within a continent–ocean transition, which decreases in width northward along the Lofoten–Vesterålen margin. To the south, the zone continues along the Vøring margin, however it is offset 70–80 km to the northwest along the Bivrost Fracture Zone/Lineament. Here, the Moho-gradient zone corresponds to a distinct, 25-km-wide, zone of rapid landward increase in crustal thickness that defines the transition between the Lofoten platform and the Vøring Basin. The continental crust on the Lofoten–Vesterålen margin reaches a thickness of 26 km and appears to have experienced only moderate extension, contrasting with the greatly extended crust in the Vøring Basin farther south. There are also distinct differences between the Lofoten and Vesterålen margin segments as revealed by changes in structural style and crustal thickness as well as in the extent of elongate potential-field anomalies. These changes may be related to transfer zones. Gravity modelling shows that the prominent belt of shelf-edge gravity anomalies results from a shallow basement structural relief, while the elongate Lofoten Islands belt requires increased lower crustal densities along the entire area of crustal thinning beneath the islands. Furthermore, gravity modelling offers a robust diagnostic tool for the existence of the lower crustal body. From modelling results and previous studies on- and off-shore mid-Norway, we postulate that the development of a core complex in the middle to lower crust in the Lofoten Islands region, which has been exhumed along detachments during large-scale extension, brought high-grade, lower crustal rocks, possibly including accreted decompressional melts, to shallower levels.  相似文献   

Reply to discussion of Gabrielsen et al. (2010) by Nielsen et al. (this volume): Latest Caledonian to present tectonomorphological development of southern Norway     

Roy H. Gabrielsen  Jan Inge Faleide  Christophe Pascal  Alvar Braathen  Johan Petter Nystuen  Bernd Etzelmuller  Sejal O'Donnell 《Marine and Petroleum Geology》2010

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Formation of intracratonic basins by lithospheric shortening and phase changes: a case study from the ultra‐deep East Barents Sea basin     

Sébastien Gac  Ritske S. Huismans  Nina S. C. Simon  Yuri Y. Podladchikov  Jan Inge Faleide 《地学学报》2013,25(6):459-464

The origin of large subsidence in intracratonic basins is still under debate. We propose a new and self‐consistent model for the formation of those basins, where lithospheric shortening/buckling triggers metamorphism and densification of crustal mafic heterogeneities. We use a forward thermo‐mechanical finite element technique to evaluate this mechanism for the typical example of the East Barents Sea basin (EBB) where a very large and compensated subsidence, accommodating an up to 20‐km‐thick sediment succession, is observed. The lower crust in the dynamic model is modelled with petrologic‐consistent densities for a wet mafic gabbroic composition that depend on pressure and temperature taking into account dehydration at high PT conditions. The model successfully explains the main characteristics of the EBB, notably the large anomalous and fast subsidence during the Late Permian–Early Triassic, its present‐day geometry and the absence of a significant gravity anomaly.  相似文献   

Editorial     

Inge Dirmhirn 《Theoretical and Applied Climatology》1987,38(1):ix-ix

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A three-dimensional geophysical model of the crust in the Barents Sea region: model construction and basement characterization   总被引：2，自引：0，他引：2  

Oliver Ritzmann  Nils Maercklin  Jan Inge Faleide  Hilmar Bungum  Walter D. Mooney  Shane T. Detweiler 《Geophysical Journal International》2007,170(1):417-435

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Multi-instrument ground-based observations of a travelling convection vortices event     

H. Lühr  M. Lockwood  P. E. Sandholt  T. L. Hansen  T. Moretto 《Annales Geophysicae》1996,14(2):162-181

A coordinated ground-based observational campaign using the IMAGE magnetometer network, EISCAT radars and optical instruments on Svalbard has made possible detailed studies of a travelling convection vortices (TCV) event on 6 January 1992. Combining the data from these facilities allows us to draw a very detailed picture of the features and dynamics of this TCV event. On the way from the noon to the drawn meridian, the vortices went through a remarkable development. The propagation velocity in the ionosphere increased from 2.5 to 7.4 km s⁻¹, and the orientation of the major axes of the vortices rotated from being almost parallel to the magnetic meridian near noon to essentially perpendicular at dawn. By combining electric fields obtained by EISCAT and ionospheric currents deduced from magnetic field recordings, conductivities associated with the vortices could be estimated. Contrary to expectations we found higher conductivities below the downward field aligned current (FAC) filament than below the upward directed. Unexpected results also emerged from the optical observations. For most of the time there were no discrete aurora at 557.7 nm associated with the TCVs. Only once did a discrete form appear at the foot of the upward FAC. This aurora subsequently expanded eastward and westward leaving its centre at the same longitude while the TCV continued to travel westward. Also we try to identify the source regions of TCVs in the magnetosphere and discuss possible generation mechanisms.  相似文献   

Untersuchungen an Sternpyranometern     

Inge Dirmhirn 《Theoretical and Applied Climatology》1958,9(2):124-148

Zusammenfassung Entwicklung, Aufbau und Funktionsweise der in Österreich verwendeten Sternpyranometer werden besprochen. Die drei gebräuchlichen Modelle werden eine strengen experimentellen Prüfung unterzogen. Augenmerk wird auf die Erfüllung bestimmter Forderungen für ein einwandfreies Funktionieren der Geräte gelenkt.Es wird gezeigt, daß die kurzwelligen Strahlungsströme in der Atmosphäre im Spektralbereich zwischen 0,3 und 3 nahezu unabhängig von der Wellenlänge und unter Erfüllung des Cosinus-Gesetzes bis zu Einfallswinkeln von 75° einwandfrei und bei Winkeln größer als 75° besser als bei anderen Pyranometern erfaßt werden. Einwirkungen der Temperatur auf die Anzeige können durch entsprechende Wahl der Kombination Geber/Leitung/Pyranometer ausgeschaltet werden. Lage des Gerätes, langwellige Temperaturstrahlungsströme und Witterungseinflüsse üben keinen Einfluß auf die Anzeige aus. Die Einstelldauer beträgt 20 Sekunden. Der Nullpunkt stellt sich ohne Depression nach Abschattung exakt ein. Die Stromausbeute ist der Bestrahlungsintensität streng proportional. Die einzelnen Geräte sind untereinander gut vergleichbar.Die Ausführungen zeigen, daß die Genauigkeit der Anzeige der hier beschriebenen Sternpyranometer den Anforderungen entspricht und daß die Instrumente sowohl bei Momentanmessungen der Globalstrahlung, der Himmelsstrahlung und der Albedo als auch bei Dauerregistrierungen einwandfreie Ergebnisse erwarten lassen.

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Summary Development, construction, and operation of star pyranometers used in Austria are discussed. The three usual models have been tested by rigorous experiments as to whether certain requirements for a correct functioning are fulfilled. It is shown that the short-wave radiation of the atmosphere in the spectral range between 0,3 and 3 is nearly independent on the wavelength and that it can be measured, in accordance with the cosine law, precisely up to angles of incidence of 75° and better than by other pyranometers with angles greater than 75°. Temperature influence on the indication of the instrument can be eliminated by choosing the right combination: receiver, circuit, pyranometer. The position of the instrument, long-wave temperature radiation, and weather conditions do not influence the indication. The time of reaction is 20 seconds. After obturation, the pointer returns exactly to zero. There is a strict proportionality between the amount of current and the radiation mtensity. Different instruments are well comparable among each other. The study shows that the accuracy of measurement of the described star pyranometers is sufficiently high and that these instruments offer correct results in case of momentaneous measurements of the global radiation, of the sky radiation, and of the albedo, as well as in case of continous recording.

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Résumé Développement, construction et fonctionnement des pyranomètres stellaires utilisés en Autriche. Contrôle expérimental sévère des trois modèles en usage. Les oxigences concernant un fonctionnement correct des instruments sont étudiées.On montre que les flux de rayonnement à courte longuer d'onde entre 0,3 et 3 de l'atmosphère sont mesurés correctement jusqu'à un angle d'incidence de 75° indépendament de la longueur d'onde et en accord avec la loi du cosinus; pour des angles supérieurs à 75° ils sont mieux mesurés qu'avec des autres pyranomètres. L'effet de température peut être éliminé par un choix convenable de la combinaison récepteur/circuit/pyranomètre. La position de l'instrument, le rayonnement à grande longueur d'onde et les phénomènes météorologiques n'ont pas d'effet sur les mesures. La durée de réaction est de 20 secondes. L'instrument revient exactement au zéro après obturation. Le courant mesuré est rigoureusement proportionnel à l'intensité de rayonnement. Les différents instruments sont aisément comparables entre eux.Ces faits montrent que l'exactitude des pyranomètres stellaires ici décrits répond aux exigences et que ces instruments fournissent d'excellents résultats tant pour la mesure instantanée du rayonnement global, du rayonnement céleste et de l'albédo que pour les enregistrements de longue durée.

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Mit 12 Textabbildungen

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Herrn Dr.Anders K. Ångström zu seinem 70. Geburtstag gewidment.  相似文献