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21.
Shao nan Zhang Knut Bj Φ rlykke 《沉积学报》2000,18(1):119-126
The timing and duration of
quartz cementation in sandstones have been mainly inferred from diagenetic texture,
relationship between pore filling minerals, fluid inclusions and isotopic data. Fluid
inclusion temperatures from North Sea reservoir sandstones indicate that most of the
quartz cement forms at temperature exceeding 90℃ and is continually proceeding after oil
emplacement, based on the fluid inclusion temperatures in quartz overgrowth which is
approaching the bottom-hole temperatures. The duration of quartz cement after oil
emplacement depends upon the saturation of porewater and the distribution of pore water
film and the property of water-wet or oil-wet of the reactants. The leaching of K-feldspar
by meteoric water requires pore water flow to move the released potassium and sodium and
silica out the solution, which suggests the mechanism does not appear to be a major source
of silica for quartz cementation. The quartz cementation coincidence with the compaction
and pressure solution suggests the major source of silica. The alteration of feldspar by
illitization of kaolinite may serve as another important source of silica at deep burial
depth. External sources are not need to call on for illustrating the quartz cementation,
because there is no evidences for large scale convection of pore water flow occurred in
the burial history of reservoir sandstones of middle Jurassic in the North Sea. 相似文献
22.
A New method for identifying possible causal relationships between CO2, total solar irradiance and global temperature change 总被引:1,自引:0,他引:1
The study compares two formulas for calculating the daily evapotranspiration ET0 for a reference crop. The first formula was proposed by Allen et al. (AL), while the second one was proposed by Katerji and Perrier with the addition of the carbon dioxide (CO2) effect on evapotranspiration (KP). The study analyses the impact of the calculation by the two formulas on the irrigation requirement (IR). Both formulas are based on the Penman-Monteith equation but adopt different approaches for parameterising the canopy resistance r c . In the AL formula, r c is assumed constant and not sensitive to climate change, whereas in the KP formula, r c is first parameterised as a function of climatic variables, then ET0 is corrected for the air CO2 concentration. The two formulas were compared in two periods. The first period involves data from two sites in the Mediterranean region within a measured climate change period (1981–2006) when all the input climatic variables were measured. The second period (2070–2100) involves data from a future climate change period at one site when the input climatic variables were forecasted for two future climate scenarios (A2 and B2). The annual cumulated values of ET0 calculated by the AL formula are systematically lower than those determined by the KP formula. The differences between the ET0 estimation with the AL and KP formulas have a strong impact on the determination of the IR for the reference crop. In fact, for the two periods, the annual values of IR when ET0 is calculated by the AL formula are systematically lower than those calculated by the KP formula. For the actual measured climate change period, this reduction varied from 26 to 28 %, while for the future climate change period, it varied based on the scenario from 16 % (A2) to 20 % (B2). 相似文献
23.
Heidi Holmgren Knut Bjørn Lindkvist 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(4):203-215
The study objective was to analyse how capitalized and non-capitalized resource rents act as mechanisms of innovation in nature-based tourism within a centre–periphery context dominated by distance, instability, and dependency. The authors studied 55 out of 64 businesses engaged in tourism in Nordkapp Municipality in Norway in the period 2002–2012. Data were collected from a survey, interviews, and empirical observations, and then analysed using both deductive and inductive methodological approaches. The main findings were that tourism in the Nordkapp Municipality had suffered from a lack of local innovation initiatives caused by the capitalized resource rent of tourism to North Cape and its leakage. Nevertheless, local tourism had increased partly because of the inclusion of new and more attractive products, due to the open-access, non-capitalized resource management in fishing tourism that operated simultaneously with the closed and capitalized context of North Cape tourism. The authors conclude that this open-access regime of fishing tourism stimulated innovation and further development of coastal tourism, and even affected traditional North Cape tourism. Non-capitalized resource rent had not leaked out because it had not been collected by external companies and because it had acted as an innovation mechanism on the periphery. 相似文献
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26.
Andreas Goldschmidt-Rokita Knut J. F. Hansch Hans B. Hirschleber Takaya Iwasaki Toshihiko Kanazawa Hideki Shimamura Markvard A. Sellevoll 《Marine Geophysical Researches》1994,16(3):201-224
The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin. 相似文献
27.
Ann-Sofi Smedman Knut Lundin Hans Bergström Ulf Högström 《Boundary-Layer Meteorology》1991,56(3):295-307
A highly mobile system for accurate measurements of wind speed and horizontal turbulence in the lowest few hundred meters of the atmosphere is presented. It consists of a light-weight sonde (only 50 g, including batteries that permit 12 h of continuous operation) which can be easily lifted by a small kite in winds below 5 m/s and up to at least 25 m/s. In winds below 5 m/s, a small kytoon may be used instead. The signals from the sonde are received by a standard FM-radio equipped with a frequency converter, and data are recorded on ordinary cassette tapes. Field tests against towermounted precision instruments were performed at two sites during neutral and unstable conditions with the sonde suspended 25 m below a small kite, the measuring heights being 11 and 18 m respectively during the two test series. Mean wind speeds are found to be accurate to within ±0.2 m/s. Wind speed spectra obtained with the flying sonde can be evaluated up to 0.5 Hz and are found to agree closely with the spectra of the longitudinal component recorded simultaneously by the tower-mounted instrument at the same height. After correction for high frequency loss, which amounted to 5% at this low height (it is expected to decrease rapidly with height), the standard deviation of the wind recorded by the sonde agreed to within 2% with that obtained by the reference instrument. A notable result of the field tests is that there was no sign of degradation of the performance of the sonde in strong turbulence conditions. 相似文献
28.
Johann Friedrich Tolksdorf Knut Kaiser 《Boreas: An International Journal of Quaternary Research》2012,41(3):408-421
Aeolian sands are widespread in the European sand‐belt. While there is a consensus about the timing of increased aeolian activity and, in contrast, of surface stabilization during the Lateglacial, knowledge about Holocene aeolian dynamics is still very sparse. It is generally assumed that aeolian processes have been closely connected to human activities since at least the Neolithic period. A compilation of 189 luminescence dates from aeolian sands of Holocene age and 301 14C‐dates from palaeo‐surfaces, comprising palaeosols, buried peats and archaeological features from the whole sand‐belt, is plotted as histograms and kernel density plots and divided into sub‐phases by cluster analysis. This is also done separately for the dates from the areas west and east of the river Elbe. Our results show that aeolian activity did not cease with the end of the Younger Dryas but continued in the whole European sand‐belt until the Mid‐Atlantic (c. 6500 a BP), presenting evidence of vegetation‐free areas at least at the local scale. During the subsequent time period evidence of aeolian sedimentation is sparse, and surface stabilization is indicated by a cluster of palaeo‐surfaces ascribed to the early Subboreal (c. 5000 cal. a BP). The agglomeration of luminescence ages around 4000 years is probably connected with intensified land use during the Late Neolithic. Younger phases of aeolian sedimentation are indicated by clusters of luminescence ages around 1800 years, a group of luminescence ages from the Netherlands and NW Germany around 900 years, and a group of ages around 680 years in Germany. Among the dates from palaeo‐surfaces, clusters were identified around 2700, 1300 and 900 cal. a BP as well as around 690 cal. a BP in the western part and 610 cal. a BP in the eastern part of the sand‐belt. The clusters within the luminescence ages and the 14C‐dates coincide with phases where increased human impact can be deduced from archaeological and historical sources as well as from environmental history. 相似文献
29.
Guidance is provided for geotechnical engineers designing civil engineering works in silty soils based on a detailed characterisation of a glaciomarine silt from Os in western Norway. It was found that these soils are susceptible to disturbance by good quality fixed piston tube sampling and care needs to be taken when using laboratory derived design parameters, particularly for consolidation and shear strength properties. A technique for assessing sample disturbance using shear wave velocity and suction measurements proved promising. Conventional techniques for determining soil strength from triaxial tests in silt are inappropriate due to the dilational nature of the material and more reliable and logical strength estimates can be made from a limiting strain criterion. Field vane data should be used with caution as measured strength, particularly remoulded values, may be high and it seems more reliable parameters can be derived from CPTU tests. One dimensional consolidation and creep of these silts can be modelled successfully by the well-known Janbu formulation. The behaviour of the Os silts does not fit easily into classical soil mechanics and published frameworks for soft soils. It seems the material is of “transitional” type and this work adds to the database of such soils which includes other natural silts and gap graded soils. For future work it is recommended that larger sample tubes (say 75 mm) with a very sharp cutting edge should be used in parallel with in situ CPTU testing. 相似文献
30.
ZHANG Shao-nan 《沉积学报》1999,17(2):263-268
Quartz cementation is a very important diagenetic event and main porosity-occluding factor in the reservoir sandstones in middle Jurassic i n North Sea. Petrological studies indicate the quartz cementation is limited in shallower burial depth and increases significantly at depth around 3.5 - 4 km. T he amount of quartz cement increases with burial depth from an average of approx imately 4%-5 vol% at 2.5 km to 17%-20 vol% at 4 km. Highest abundances of quartz cement exceeds 28% which has been found in the Ness Formation. Variations in qu artz cementation between different sandstone facies is minimal for any one forma tion, with exception of the generally lower quantities present in the heterolith ic sandstone. Homogenisation temperatures of fluid inclusion in quartz overgrowt h from the North Sea reservoirs indicate that few quartz cement occur below the temperature 70 ℃~80 ℃, the onset of large volume quartz cement starts at the temperatures higher than 90 ℃ which suggests the quartz cementation is temperat ure - dependent during progressing diagenesis of sandstones. 相似文献