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31.
George E.J. Beckmann Niels Ø. Olesen Kai Sørensen 《Earth and Planetary Science Letters》1977,36(2):269-279
In the Nordre Strømfjord shear zone of central West Greenland it is believed that the gneisses exposed at the coast reached a maximum depth of burial about 10 km deeper than those now adjacent to the inland ice. This theory was tested palaeomagnetically. Further sampling up the mountain K?llingeh?tten was carried out to ascertain changes of direction of magnetization with height.The magnetic susceptibility ellipsoids were determined for each specimen and were used to correct their directions of magnetization for the effects of anisotropy. Complicated but compact polar wander paths were derived for both the fjord and mountain traverses. The path for the fjord is consistent with the geological model but does not support it. This inconclusive result may be the consequence of a low rate of polar wander. The mean palaeomagnetic poles are 27.7°N, 276.6° E (dp = 13.8°,dm = 17.3°) for Nordre Strømfjord and 25.3°N, 300.4°E (dp = 11.5°,dm = 14.1°) for K?llingeh?tten. 相似文献
32.
A combination of R-mode factor residual, factor score, and univariate screening methods is more successful than univariate screening (based on cumulative frequency curves) alone in identifying outliers and sharpening definition of background populations. The factor models for the screened data sets are more easy to interpret than those for the original data sets, and are used to check the background nature of the screened populations. The resulting data sets can be used either for statistical evaluation of single-element data, or as training sets for multivariate classification. The screening method is illustrated with stream-sediment data from South Greenland. 相似文献
33.
When the Regional Advisory Councils (RACs) were created during the last reform of the Common Fisheries Policy (CFP) in 2002, it was recognised that in addition to the five geographically orientated stakeholder lead advisory bodies, a separate RAC dedicated exclusively to pelagic fisheries was needed because of it being so distinctly different from other fisheries. Pelagic fishing is different mostly due to the fact that the targeted fish species behave in a unique manner by grouping in schools in mid-water unlike other commercially targeted fishes, which typically reside on or near the ocean floor. For this reason, as well as the fact that they are usually widely distributed, researching and managing this dynamic group of fishes across the borders of many countries requires a unique approach. Fortunately, despite these complexities, policy makers have succeeded to establish a reasonably well functioning management framework, which has lead to the situation that most pelagic fish stocks are harvested biologically sustainable. While a majority of Europe's fish stocks still need rebuilding, and the main aim accordingly is to reduce fishing mortality, the current focus for pelagic fish stocks is to improve the performance of already implemented Long Term Management plans in terms of their biological as well as social and economical objectives. This paper reflects upon experiences of the Pelagic Regional Advisory Council (PRAC) in its role as advisor to the EU institutions. Subsequently, in the context of ideas presented in the European Commission's Green paper, the authors discuss the future of the PRAC and conclude that its main development potential lies not with the current EU's CFP reform, but rather should be sought in a wider international context. 相似文献
34.
We challenge some of the long-standing beliefs related to the Permian Oslo Rift structure, often referred to as a case example/type locality for continental rifting. The crustal structure of the Oslo Rift was long presumed to be thinned Proterozoic crust overlying a Permian high-density layer, interpreted as magmatic underplating. New data support an alternative view of the crustal structure in the Oslo Rift region. The Bouguer gravity high in the region shows a strong asymmetry: a steep, westward-facing gradient to the west of the rift, and a much gentler eastern gradient. We present a 3D density model based on petrophysical and seismic information, which accounts for the Bouguer gravity high using an eastward extension of old Precambrian structures, without invoking a prominent magmatic underplated structure. Reactivation of old pre-rift structures appears to be an important feature, affecting the evolution and location of the Permo-Carboniferous Oslo Rift. 相似文献
35.
L. Rise O. Olesen K. Rokoengen D. Ottesen F. Riis 《Quaternary Science Reviews》2004,23(23-24):2323-2335
Several investigations have shown that a huge Late Weichselian ice stream flowed along the Norwegian Channel, and deposited thick debris flow deposits at the North Sea Fan. The development of the channel is probably mainly a result of several cycles of ice stream activity during the Quaternary. A merged 3D seismic image shows a lineated relief pattern interpreted as a uniquely well-preserved footprint of a moving ice sheet. This deep Quaternary horizon corresponds to a slightly irregular reflector on top of a parallel-layered seismic sequence. Seismic tie to the Troll core 8903 south of the study area shows that the sequence comprises Early Middle Pleistocene marine sediments. The pattern of lineations, the seismic stratigraphy, as well as the chronostratigraphic investigations of the Troll core, strongly indicate that the image reflects the initial phase of an extensive Middle Pleistocene glaciation (inferred age ca 0.5 Ma), prior to the development of a massive Norwegian Channel Ice Stream. The northwesterly oriented pattern, seen in the southeastern part of the study area, demonstrates that the ice flowed into the channel mainly from the coastal zone north of Bergen. Farther west various sets of ‘fan-shaped lineations’ partly cross each other, showing that the 3D-image represents a certain short time window. In the northern study area the ice flow was dominantly northwards, and directed towards the area below the present shallow Måløy Plateau. There are no indications that the glaciers north of Sognefjorden affected the marine ice sheet. 相似文献
36.
37.
The Northern and Southern Scandes — structural differences revealed by an analysis of gravity anomalies, the geoid and regional isostasy 总被引：1，自引：1，他引：1
We investigate the Scandes mountain range by analysing the gravity field, the geoid heights and the degree of isostatic compensation of the lithosphere. Topographically, the Scandes mountain range can be divided in the Northern and Southern Scandes. Comparisons between the present topographic expression and the gravity field and the geoid show that the axis of highest elevation in the Northern Scandes is shifted eastwards compared to the minimum of the Bouguer anomaly, while the two coincide perfectly in the Southern Scandes. Geoid heights reduced by the effect of topographic masses show a large-scale minimum in the Northern Scandes, but no anomaly in the Southern Scandes.Regional, flexural isostatic calculations yield a flexural rigidity of D = 1023 Nm for the lithosphere of the Southern Scandes and the isostatic gravity and geoid residuals point to additional isostatic support by low-density rocks below the Moho. On the other side, for the lithosphere in the Northern Scandes no significant flexural rigidity can be resolved. Here, the Bouguer anomaly is best modelled with a small flexural rigidity, indicating nearly Airy isostatic behaviour. Local subsurface loading and horizontal tectonic forces overprint the isostatic compensations and increase the tectonic complexity of the Northern Scandes. These distinctive features of the Scandes cannot be explained by currently existing models of the present and Neogene uplift and the isostatic mechanism of the Scandes. 相似文献
38.
A comparison of stable platform and strapdown airborne gravity 总被引：3，自引：1，他引：2
C. L. Glennie K. P. Schwarz A. M. Bruton R. Forsberg A. V. Olesen K. Keller 《Journal of Geodesy》2000,74(5):383-389
To date, operational airborne gravity results have been obtained using either a damped two-axis stable platform gravimeter
system such as the LaCoste and Romberg (LCR) S-model marine gravimeter or a strapdown inertial navigation system (INS), showing
comparable accuracies. In June 1998 three flight tests were undertaken which tested an LCR gravimeter and a strapdown INS
gravity system side by side. To the authors' knowledge, this was the first time such a comparison flight was undertaken. The
flights occurred in Disko Bay, off the west coast of Greenland. Several of the flight lines were partly flown along existing
shipborne gravity profiles to allow for an independent source of comparison of the results. The results and analysis of these
flight tests are presented. The measurement method and error models for both the stable platform and strapdown INS gravity
systems are presented and contrasted. An intercomparison of gravity estimates from both systems is given, along with a comparison
of the individual estimates with existing shipborne gravity profiles. The results of the flight tests show that the gravity
estimates from the two systems agree at the 2–3 mGal level, after the removal of a linear bias. This is near the combined
noise level of the two systems. It appears that a combination of both systems would provide an ideal airborne gravity survey
system, combining the excellent bias stability of the LCR gravimeter with the higher dynamic range and increased spatial resolution
of the strapdown INS.
Received: 3 June 1999 / Accepted: 30 November 1999 相似文献