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1.
Christoffer Oftedahl 《International Journal of Earth Sciences》1959,48(1):18-26
The Permian activity in the Oslo region started with lava effusions. Monzonitic rhomb porphyry flows predominate, with basaltic flows inbetween. Then a number of basalt volcanoes formed. This phase ended in explosive volcanism, producing ignimbrites, and the explosive activity is considered the primary cause for formation of at least four large and a few smaller cauldrons (or calderas). Below the lava surface monzonitic magma and associated syenitic and granitic magmas crystallized to larvikite, nordmarkitic and granitic rocks. These magmas are assumed to be formed by local melting of portions of the lower crust. The mode of emplacement is stoping. 相似文献
2.
Christoffer Bostrm Emma L. Jackson Charles A. Simenstad 《Estuarine, Coastal and Shelf Science》2006,68(3-4):383
Seagrasses comprise some of the most heterogeneous landscape structures of shallow-water estuarine/marine ecosystems in the world. However, while knowledge at the molecular, organism, patch and community scale is pervasive, understanding of seagrass landscape ecology is more fragmentary and has not been synthesized. The growth and recruitment dynamics of seagrasses as well as man-made and/or natural disturbances create complex spatial configurations of seagrass over broad (metres to kilometres) spatial scales. Hence, it is important to identify mechanisms maintaining and/or threatening the diversity-promoting function of seagrass meadows and to understand their effects on benthic populations and communities. Although landscape ecology has recently become more integrated into seagrass research, our understanding of animal responses to variability in seagrass landscape structure is still fragmentary. By reviewing the literature to date, this paper evaluates studies on seagrass landscape ecology, testing the general null hypothesis that concepts developed in terrestrial settings can be generalized across landscapes, and (a) presenting definitions and terms used in seagrass landscape ecology, (b) reviewing geographical patterns of seagrass landscape studies to identify possible key regions and target species, (c) evaluating different methodological approaches, (d) describing the spatial and temporal scales used to describe organism responses to seagrass landscape structure, and (e) placing seagrass landscapes into an applied context. 相似文献
3.
Prof. Dr. Christoffer Oftedahl 《International Journal of Earth Sciences》1967,57(1):203-218
Zusammenfassung Kartierung seit 1960 hat gezeigt, daß das Vestfold Lava-Gebiet im südlichen Teil des Oslo-Grabens stratigraphisch viel umfassender ist als früher gefunden. Zwar findet man hier 26 Lava-Ströme von Rhombenporphyr, 5 Basaltströme und 3 Trachytlaven. Jünger sind ungefähr 1000 m von Rhyolitströmen in der im Süden gelegenen Ramnes-Caldera. Noch jünger ist das große Larvikitfeld im südlichen Oslo-Gebiet. Ganz wie die Plutonite sich von intermediärer Zusammensetzung bis saurer bewegen, verändern sich auch gradweise die Vulkanite in ihrer Zusammensetzung von intermediärer bis saurer während des Larvikit-Magmatismus.Für die totale Magmenbildung des Oslo-Grabens gibt es im Lichte der letzten Ergebnisse aus dem Graben sowie aus der Literatur die folgenden Möglichkeiten: 1. Tiefkrustale anatektische Magmenbildung, die sich oben bewegt, mit gradweise saureren Produkten. 2. Tiefkrustale anatektische Magmenbildung begleitet von tiefkrustaler gravitativer Differentiation. 3. Tiefkrustale Magmenbildung mit weitgehender oberflächennaher Differentiation. 4. Basaltische Magmen aus dem oberen Mantel, die einer weitgehenden krustalen Differentiation unterliegen. 5. Mögliche Differentiation im oberen Mantel von Mantel-Magmen.
Mapping in the Vestfold lava area in the southern part of the Oslo Graben has revealed a lava stratigraphy consisting of 26 rhomb porphyry flows, 5 basalt lavas and 3 trachyte lavas. A thickness of about 1000 m of rhyolite flows within the Ramnes caldera is younger than the rhomb porphyries. Still younger is the large area of larvikite in the southernmost part of the Oslo Region. Thus the volcanics show a continuous series from intermediate to acidic composition just as the plutonic rocks, although all volcanic eruptions happened within the larvikite phase of the plutons.The magma formation within the Oslo Graben may be explained within the following possibilities: 1. Anatectic magma formation in the deeper crust, moving upwards and changing gradually to more acidic products. 2. Anatectic magma formation in the deeper crust, accompanied by gravitative differentiationin situ. 3. Magma formation in the deeper crust, with comprehensive differentiation near the surface. 4. Basaltic magmas from the upper mantle, undergoing a comprehensive crustal differentiation. 5. Possible differentiation in the upper mantle.
Résumé La documentation cartographique a montré que l'étendue de la lave de Vestfold au sud du fossé d'Oslo est beaucoup plus grande qu'où avait supposé jusqu'ici. On y trouve 26 courants de lave à rhombes porphyriques, 5 courants de basalte et 3 laves trachytiques. Les 1000 m de lave rhyolitique de la Ramnes-Caldera au sud sont plus récents. Encore plus récent est le vaste champ de larvikite au sud d'Oslo. Les plutonites changeaient d'une composition intermédiaire à une composition acide de même que les volcanites, mais celles-ci pendant le magmatisme du larvikite.La formation du magma dans le fossé d'Oslo pent être expliquée par les plus récents résultats du fossé ainsi que par la littérature. Les possibilités sont: 1. Formation anatectique de magma dans une croûte profonde qui monte et devient de plus en plus acide. 2. Formation anatectique de magma dans une croûte profonde accompagnée d'une différentiation gravitative in situ. 3. Formation de magma dans une croûte profonde à différentiation près de la surface. 4. Des magmas basaltiques du manteau supérieur sujets à une différentiation largement crustale. 5. Différentiation possible au manteau supérieur.
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4.
In the 200 km by 45 km area of exposed Permian rocks of the Oslo rift of southern Norway, 15 and possibly 18, cauldrons occur within a rift length of 180 km. These cauldrons range in size from 5 to 16 km in diameter and average around 10–12 km. They exhibit ring dikes, central intrusions, caldera depression deposits (ignimbrites, breccias, lake sediments), and cannibalism of the subsided block by younger, stoping plutons. Only six cauldrons retain most of their periphery, three have lost half their original area to younger plutons, and nine show up as segments or crescents.Ring dikes are mostly syenitic, and central intrusions range from monzonitic to syenitic, with some granitic plugs. The caldera blocks seem to have subsided into monzonitic magma chambers with a differentiated top layer of syenitic magma. Subsidence is assumed to have been started by large-scale crustal movements with a slight tensional component that produced subsidence in the uppermost parts of the magmatic plumbing system. Blocks having thicknesses of 2–5 km above these uppermost magma chambers dropped along sharp ring faults. Absence of resurgent domes is due to composition (and viscosity) of the underlying magmas: these intermediate magmas stoped their way up, without doming. Cauldrons with magmas of intermediate composition make up a major group, between the basaltic shield cauldrons and the resurgent type that produced ignimbrites. 相似文献
5.
Lars Frlin Lennart Balk Malin Celander Sture Bergek Maria Hjelt Christoffer Rappe Cynthia de Wit Bo Jansson 《Marine environmental research》1992,34(1-4)
Recently, analysis of organochlorines in sediment and in pike from Lake Vänern, Sweden, showed a north-south gradient of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In the present study, good correlations were found between muscle 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents and liver ethoxyresorufin-O-deethylase (EROD) activities (and P4501A levels) in pike caught at three sampling sites along the north-south gradient in the lake. This comparison between tissue levels of PCDD/PCDF and EROD activity (and P4501A) may indicate that TCDD or structural analogs could be responsible for the observed induction of the pike P450 system. It must, however, be taken into account that the analysed contaminants often do not appear alone but are, rather, accompanied by a range of other substances which may be inducers or antagonists. 相似文献
6.
Benthic samples from coastal locations off Southwestern Norway were examined and the specimens of Thyasiridae were identified to species. A multivariate analysis based on 13 parameters was carried out and the environmental preferences of all thyasirid species present were determined. The potential of the Thyasiridae as indicators of organic enrichment was investigated by using direct canonical correspondence analyses to identify correlations between selected environmental parameters and the collected biological data. The presence of Thyasira sarsi together with a low biodiversity is a good indicator of organic enrichment. High thyasirid species diversity seems to indicate good environmental conditions, and single thyasirid species that lack symbiotic bacteria might also be useful as indicators of good environmental conditions. 相似文献
7.
A measuring car, the rolling stiffness measuring vehicle (RSMV), has been developed to investigate track conditions. The investigation described in this paper firstly attempts to understand whether the point flexibility of the track, i.e., the track-embankment-subsoil system, can be obtained by simultaneously measuring the force applied to an axle of the measuring car and the resulting acceleration response. Secondly, it attempts to determine the physical properties of the track by modelling it as a Bernoulli–Euler beam on a Kelvin foundation. The final part of the paper investigates the possibility of predicting displacements on a railway embankment based on the physical properties obtained after a train passage. Results from two sites in Sweden, Kumla and Kåhög, have been used. Investigations give encouraging results. However, as seen here, it can be difficult to analyse and obtain parameters if the resonance frequency of the system is low. The peak particle displacement of the ballast on the railway embankment was achieved with fair accuracy for both Kumla and Kåhög using the results from the accelerometer on the RSMV. 相似文献
8.
Huidong Li Bj?rn Claremar Lichuan Wu Christoffer Hallgren Heiner K?rnich Stefan Ivanell Erik Sahlée 《地学前缘(英文版)》2021,12(6):209-222
Accurate wind modeling is important for wind resources assessment and wind power forecasting.To improve the WRF model configuration for the offshore wind modeling over the Baltic Sea,this study per-formed a sensitivity study of the WRF model to multiple model configurations,including domain setup,grid resolution,sea surface temperature,land surface data,and atmosphere-wave coupling.The simu-lated offshore wind was evaluated against LiDAR observations under different wind directions,atmo-spheric stabilities,and sea status.Generally,the simulated wind profiles matched observations,despite systematic underestimations.Strengthening the forcing from the reanalysis data through reducing the number of nested domains played the largest role in improving wind modeling.Atmosphere-wave cou-pling further improved the simulated wind,especially under the growing and mature sea conditions.Increasing the vertical resolution,and updating the sea surface temperature and the land surface infor-mation only had a slight impact,mainly visible during very stable conditions.Increasing the horizontal resolution also only had a slight impact,most visible during unstable conditions.Our study can help to improve the wind resources assessment and wind power forecasting over the Baltic Sea. 相似文献
9.
Prof. Dr. Christoffer Oftedahl 《International Journal of Earth Sciences》1968,57(3):920-930
It seems possible to locate some of the volcanic centres of the greenstone effusions of the Caledonian geosynclinal volcanism in Norway from simple geologic features, such as greenstone thickness and character, gabbro intrusion intensity, and quartz keratophyre frequency. In the central part of the Trondheim region some six probable and four likely volcanoes are indicated. The best example may be the upturned Joma volcano further north.
Dedicated to Professor Dr. A.Rittmann on the occasion of his 75. birthday 相似文献
Zusammenfassung Es scheint möglich, einige der vulkanischen Zentren der Grünsteineffusionen im Vulkanismus der kaledonischen Geosynklinale durch einfache geologische Merkmale wie Mächtigkeit und Charakter des Grünsteins, Intensität der Gabbrointrusion und Häufigkeit der Quarzkeratophyre aufzufinden. Im Mittelteil des Trondheimgebietes werden 6 wahrscheinliche und 4 mögliche Vulkane angegeben. Das beste Beispiel wäre vielleicht der umgekehrte Joma Vulkan weiter nördlich.
Résumé Il semble probable de localiser quelques-uns des centres volcaniques des émissions de « greenstone » dans le volcanisme géosynclinal calédonien en Norvège d'après des marques géologiques comme l'épaisseur et le caractère de «greenstone», l'intensité de la gabbro intrusion, et la fréquence de quartz kératophyre. Au milieu de la Trondheim région on constate six volcans probables et quatre volcans possibles. Le meilleur exemple est peut-être le Joma volcan renversé plus au nord.
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Dedicated to Professor Dr. A.Rittmann on the occasion of his 75. birthday 相似文献
10.
Lower crustal intrusions beneath the southern Baikal Rift Zone: Evidence from full-waveform modelling of wide-angle seismic data 总被引：1，自引：0，他引：1
The Cenozoic Baikal Rift Zone (BRZ) is situated in south-central Siberia in the suture between the Precambrian Siberian Platform and the Amurian plate. This more than 2000-km long rift zone is composed of several individual basement depressions and half-grabens with the deep Lake Baikal at its centre. The BEST (Baikal Explosion Seismic Transect) project acquired a 360-km long, deep seismic, refraction/wide-angle reflection profile in 2002 across southern Lake Baikal. The data from this project is used for identification of large-scale crustal structures and modelling of the seismic velocities of the crust and uppermost mantle. Previous interpretation and velocity modelling of P-wave arrivals in the BEST data has revealed a multi layered crust with smooth variation in Moho depth between the Siberian Platform (41 km) and the Sayan-Baikal fold belt (46 km). The lower crust exhibits normal seismic velocities around the rift structure, except for beneath the rift axis where a distinct 50–80-km wide high-velocity anomaly (7.4–7.6 ± 0.2 km/s) is observed. Reverberant or “ringing” reflections with strong amplitude and low frequency originate from this zone, whereas the lower crust is non-reflective outside the rift zone. Synthetic full-waveform reflectivity modelling of the high-velocity anomaly suggests the presence of a layered sequence with a typical layer thickness of 300–500 m coinciding with the velocity anomaly. The P-wave velocity of the individual layers is modelled to range between 7.4 km/s and 7.9 km/s. We interpret this feature as resulting from mafic to ultra-mafic intrusions in the form of sills. Petrological interpretation of the velocity values suggests that the intrusions are sorted by fractional crystallization into plagioclase-rich low-velocity layers and pyroxene- and olivine-rich high-velocity layers. The mafic intrusions were probably intruded into the ductile lower crust during the main rift phase in the Late Pliocene. As such, the intrusive material has thickened the lower crust during rifting, which may explain the lack of Moho uplift across southern BRZ. 相似文献