The Taimyr fold belt, Arctic Siberia: timing of prefold remagnetisation and regional tectonics     

Trond H. Torsvik  Torgeir B. Andersen 《Tectonophysics》2002,352(3-4)

Late Precambrian and Palaeozoic platform sediments from the Central–South Taimyr Peninsula (Arctic Siberia) are all remagnetised. The remagnetisation is prefold and is related to thermal remagnetisation caused by Taimyr Trap magmatism. The remagnetisation age is estimated to 220–230 Ma and, hence, is considerably younger than the ca. 251 Ma age for the main body of Siberian Trap flood basalts. The folding that affected the Taimyr region platform sediments also included the Taimyr “Traps,” hence, relegating Taimyr deformation to post-Mid Triassic time, and most probably, to a Late Triassic age. This shows that whilst thrusting terminated in the Urals during the Permian, crustal shortening continued in Taimyr, Novaya–Zemlya and the South Barents Sea, well into the Mesozoic.  相似文献   

Structural geology of the Huldra Field, northern North Sea—a major tilted fault block at the eastern edge of the Horda Platform     

Haakon Fossen  Jonny Hesthammer  Tord Erlend Skeie Johansen  Trond Olav Sygnabere 《Marine and Petroleum Geology》2003,20(10):1105-1118

The Huldra fault block is a rotated major fault block on the east margin of the Viking Graben in the northern North Sea. Unlike the rest of the Horda Platform area, the Jurassic section in the Huldra fault block was rotated more than 20° during slip on the listric Huldra fault, which forms a low-angle detachment beneath the Huldra fault block. The fault block is interpreted as resulting from marginal collapse of the Horda Platform after relief along the eastern margin of the Viking Graben built up in early parts of the middle to late Jurassic rifting history. The collapse resulted in NW directed transport of the Huldra fault block, consistent with a previously postulated change in extension direction from W–E to NW–SE toward the end of the Jurassic period. Minor faults within the Hulrda fault block are consistent with E–W extension and thus may have formed early during the late Jurassic rifting phase. Nevertheless, the crest (Huldra Field) seems surprisingly intact, considering its proximity to a major fault zone. Deformation bands studied from core material are non-cataclastic and concentrated in zones. Evidence for smearing along a cored fault surface indicates that minor subseismic faults may be sealing. Production data from the field indicate good communication between most wells, suggesting that the subseismic faults and deformation band zones that are present in the reservoir have relatively small influence on the flow of gas in the reservoir.  相似文献   

Differing susceptibility of anadromous brown trout (Salmo trutta L.) populations to salmon louse (Lepeophtheirus salmonis (Kroyer, 1837)) infection     

Glover  K.A; Skaala  O; Nilsen  F; Olsen  R; Teale  A.J; Taggart  J.B 《ICES Journal of Marine Science》2003,60(5):1139-1148

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Turbidites in the Upper Carboniferous Ross Formation, western Ireland: reconstruction of a channel and spillover system   总被引：2，自引：0，他引：2  

Trond Lien  Roger G. Walker†  Ole J. Martinsen 《Sedimentology》2003,50(1):113-148

ABSTRACT The Upper Carboniferous deep‐water rocks of the Shannon Group were deposited in the extensional Shannon Basin of County Clare in western Ireland and are superbly exposed in sea cliffs along the Shannon estuary. Carboniferous limestone floors the basin, and the basin‐fill succession begins with the deep‐water Clare Shales. These shales are overlain by various turbidite facies of the Ross Formation (460 m thick). The type of turbidite system, scale of turbidite sandstone bodies and the overall character of the stratigraphic succession make the Ross Formation well suited as an analogue for sand‐rich turbidite plays in passive margin basins around the world. The lower 170 m of the Ross Formation contains tabular turbidites with no channels, with an overall tendency to become sandier upwards, although there are no small‐scale thickening‐ or thinning‐upward successions. The upper 290 m of the Ross Formation consists of turbidites, commonly arranged in thickening‐upward packages, and amalgamated turbidites that form channel fills that are individually up to 10 m thick. A few of the upper Ross channels have an initial lateral accretion phase with interbedded sandstone and mudstone deposits and a subsequent vertical aggradation phase with thick‐bedded amalgamated turbidites. This paper proposes that, as the channels filled, more and more turbidites spilled further and further overbank. Superb outcrops show that thickening‐upward packages developed when channels initially spilled muds and thin‐bedded turbidites up to 1 km overbank, followed by thick‐bedded amalgamated turbidites that spilled close to the channel margins. The palaeocurrent directions associated with the amalgamated channel fills suggest a low channel sinuosity. Stacks of channels and spillover packages 25–40 m thick may show significant palaeocurrent variability at the same stratigraphic interval but at different locations. This suggests that individual channels and spillover packages were stacked into channel‐spillover belts, and that the belts also followed a sinuous pattern. Reservoir elements of the Ross system include tabular turbidites, channel‐fill deposits, thickening‐upward packages that formed as spillover lobes and, on a larger scale, sinuous channel belts 2·5–5 km wide. The edges of the belts can be roughly defined where well‐packaged spillover deposits pass laterally into muddier, poorly packaged tabular turbidites. The low‐sinuosity channel belts are interpreted to pass downstream into unchannellized tabular turbidites, equivalent to lower Ross Formation facies.  相似文献   

Comment on “Palaeomagnetic results from volcanic rocks of the Shelve Inlier, Wales: evidence for a wide Late Ordovician Iapetus Ocean in Britain” by C. McCabe and J.E.T. Channell     

Allan Trench  Trond H. Torsvik 《Earth and Planetary Science Letters》1991,104(2-4)

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Photogrammetric tracking of tracer particles in modelled ocean flows     

Jan H Nilsen  Ingolf Hdem 《ISPRS Journal of Photogrammetry and Remote Sensing》1994,49(6)

Three-dimensional particle tracking velocimetry (3D-PTV) has been used to quantify simulated ocean circulation and internal waves, in a 5 m diameter rotating tank. According to hydrostatic theory the water surface in the rotating tank will attain the surface of an elliptic paraboloid of revolution. Three “off the shelf” video cameras mounted above the water surface, rotating with the tank, monitored the 3D displacements of sparsely distributed surface and neutrally buoyant submerged particles (diameter of 0.01 m) inside a water volume of ca. 0.5 × 0.7 × 0.5 m³. A numerical procedure for the calibrations of the photogrammetric system is described. The particles were automatically tracked through a time series of consistent image triplets using an epipolar approach. The experiments gave a standard error σ_o = 0.33 pixels and a repetition accuracy, RMSE = 0.15 mm in X, Y and 0.5 mm in Z (the height).  相似文献   

The potential of natural ecosystem self-purifying measures for controlling nutrient inputs     

Petter D. Jenssen  Trond M  hlum  Roger Roseth  Bent Braskerud  Nina Syversen  Arnor Nj  s  Tore Krogstad 《Marine pollution bulletin》1994,29(6-12):420-425

Most ecosystems have a certain assimilative capacity regarding plant nutrient or biodegradable organic matter. Knowledge of the metabolizing processes of different ecosystems enable the use of natural systems for pollution abatement from agricultural, domestic and industrial sources. Such ecologically engineered natural systems are often very cost efficient. At the Centre for Soil and Environmental Research (JORDFORSK) studies of degradation processes and the fate of plant nutrients in small streams, ponds, wetlands, vegetative filter strips and soil are being conducted in order to gain experience with and develop self purifying methods. Preliminary results show that denitrification in streams remove only a minor part of the annual nitrogen (N) transport (1–15%), but that this process can remove a considerable part of the N transport during summer. Constructed ponds and wetlands in streams draining agricultural areas showed 10–56% retention of soil particles, 23–40% of phosphorous (P) and 5–13% of N. Narrow ponds had a higher efficiency than wide ponds per unit surface area. Short-term experiments with vegetative strips treating agricultural runoff show a sediment removal of over 95%, a P removal from 80–90% and N removal between 60 and 75%. A multistage subsurface constructed wetland treating domestic waste-water removed an average of 97% P, 91% BOD, 80% of suspended solids, 55% N and 99.9% E. coli over the first 18 months of operation. Preliminary results from a multistage plant with constructed ponds and wetlands treating landfill leachate show high treatment efficiency for the same parameters. A rapid infiltration plant in northern Norway showed an average removal of 99% P, 90% COD and 73% N after 4 years of operation. These results show that self purifying measures offer potential for design of pollution abatement systems for agricultural as well as domestic purposes in the Norwegian climate.  相似文献   

Analysis of potential cave-in from fault zones in hard rock subsea tunnels     

Prof. Dr. B. Nilsen 《Rock Mechanics and Rock Engineering》1994,27(2):63-75

Summary As a part of a research program on the rock engineering aspects of hard rock subsea tunnelling, analyses of potential cave-in from fault zones have been carried out at the Norwegian Institute of Technology. This is a topic of great importance for the planning of future subsea tunnels, and particularly for the selection of the minimum rock cover of such projects. The paper is divided into three main parts: a) review of cases of instability in Norwegian subsea tunnels, b) evaluation of theoretical maximum sliding, and c) discussion of cases of cave-in in tunnels under land. In theory, a cave-in during subsea tunnelling may propagate far higher than the normal minimum rock cover. Taking into consideration the comprehensive geo-investigations that are always carried out for subsea tunnel projects today, it would, however, be unrealistic to base the dimensioning of rock cover for future projects on worst-case scenarios. Consequently, the main result of this study is to emphasize the importance of comprehensive geo-investigations, detailed tunnel mapping, a high degree of readiness during tunnelling and a thorough quality control.  相似文献   

Numerical Analysis of the 650,000 m<Superscript>2</Superscript> Åknes Rock Slope based on Measured Displacements and Geotechnical Data     

Vidar Kveldsvik  Herbert H. Einstein  Bjørn Nilsen  Lars Harald Blikra 《Rock Mechanics and Rock Engineering》2009,42(5):689-728

The unstable 650,000 m² Åknes rock slope (Western Norway) poses a hazard, as a sudden failure may cause a destructive tsunami in the fjord. In this study the slope was divided into blocks based on displacements measured at the slope surface. Discontinuous deformation analysis (DDA) showed that three or four blocks in the upper half may be considered as potential subareas that may fail catastrophically. The lower half may be divided into two or three blocks, but more limited data introduces more uncertainty into block definition. The Universal Distinct Element code (UDEC) was used for two-dimensional (2D) stability analyses. By varying fracture geometry, fracture friction, and groundwater conditions within reasonable limits based on site-specific data a number of possible models were compared. The conclusions show that models that were unstable to great depths were in closer agreement with shear strength parameters derived from an earlier study than models that were unstable to smaller depths. The length (depth) of the outcropping fracture, along which shear displacements are shown to occur, plays an important role. A (shallow) slide at 30 m, in which displacements have been documented by borehole measurements, will reduce the stability at greater depths. Increased groundwater pressure is demonstrated to be less critical for very deep slope instability. The results of the DDA and UDEC modelling will be useful for planning of future investigations, interpretation of the subsequent results, further development of the early warning system and in the tsunami modelling.  相似文献   

International viewpoint and news     

Dirk Notz  Peter Haugan  Karolina Widell  Frank Nilsen  Anne Marie de Grosbois 《Environmental Geology》2009,57(2):479-481

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