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11.
The interpretation protocols for defining offshore rifted margin architecture normally include seismic‐reflection analysis supplemented by refraction and/or potential field modelling to help constrain sedimentary, basement and Moho geometries at depth and/or the presence of magmatic material. Interpretation of modern high‐resolution long‐offset reflection profiles shows that significant mismatches may arise between the structural observations made from these data and the common translation of density, magnetic or velocity values into specific rock types made by geophysical models. We illustrate this problem with three examples from the Mid‐Norwegian rifted system, and discuss the implications with respect to the geological interpretation. 相似文献
12.
Raymond S. Eilertsen Louise Hansen Terje H. Bargel Inger-Lise Solberg 《Geomorphology》2008,93(3-4):548-562
The distribution of a large number of clay slides in the Målselv valley, northern Norway, is analysed and put into context with the stratigraphic organization of the valley-fill sediments. About 32% of the landslides larger than 104 m3 occur close to the valley margins, where mud is either exposed or at shallow depth. About 57% of the landslides occur mid-valley, where relatively thin (< 15 m) coarse-grained deltaic sediments overlay fine-grained marine and glaciomarine sediments, and about 11% of the landslides occur in front of ice-contact deposits. The slide-prone areas are all characterized by the occurrence of heterogeneous sediments (interbedded clay, silt and sand), in addition to the presence of steep slopes eroded by rivers. The heterogeneous nature of the sediments probably enhanced groundwater drainage and leaching of salts from the clay, increasing sensitivity. Thus, the distribution and organization of the valley-fill sediments and groundwater drainage probably controlled the position of the slide scars and sliding planes. Since deglaciation of the valley (11,500 BP–present), isostatic rebound has enhanced fluvial incision and the creation of steep slopes due to a fall in relative sea level of up to 80 m.Arcuate-shaped, ‘bottleneck’ landslide scars ranging from c. 104 to 107 m3 in size is the dominant morphological signature of the slides, typical for quick clay slides or earth flows involving fluid mud. Their most common triggering mechanism is probably erosion at the toe slopes by the river Målselv or its tributaries. River erosion close to the valley margin, where glaciomarine and marine sediments are present, seems to give the most severe slides. The overall valley-fill organization controls the distribution of clay slides, which may apply to other fjord valleys having similar sediment distribution. 相似文献
13.
Jörg Ebbing Laurent Gernigon Christophe Pascal Odleiv Olesen Per Terje Osmundsen 《Geophysical Prospecting》2009,57(4):665-681
We discuss the correlation between the depth extent of magnetic sources, the Curie temperature depth and crustal structures on the mid-Norwegian margin. Spectral methods can be used to estimate the depth extent of magnetic sources, even if the bottom is located in the lower crust, however, only with limited resolution. The bottom of the magnetic surfaces is often regarded to represent the depth to the Curie isotherm. However, comparison with a 3D model based on the interpretation of potential field and seismic reflection data and thermal modelling shows that the depth extent of the magnetic sources is merely controlled by the overall geometry of the crystalline crust and not the temperature distribution. The observed changes in the magnetic field between the inner and outer part of the mid-Norwegian margin appears not to reflect, as previously assumed, the depth to the Curie temperature but the geometry of the basement and lower crust. Our 3D model of the mid-Norwegian margin reveals a basement configuration that involves a basement with different petrophysical properties, which can be connected with lithological basement units of onshore Norway. 相似文献
14.
This article uses the concepts of "human stewardship" and "ruined landscape" as a theoretical framework for analysing the community's perception of landscape change in the ancient tula well system of Borana in southern Ethiopia. The ancient tula well system, the main permanent water source, has been in operation for more than five centuries and it closely links human activity and the environment. The welfare of the tula well system and the performance of the Borana pastoral system are directly related. Borana management of the tula wells uses concepts such as laaf aadaa seeraa and laaf bade to differentiate between ‘land managed by customary laws’ (hereafter human stewardship) and ‘lost’ or ‘ruined’ land (laaf bade). The cultural landscapes of the ancient wells have undergone changes from ecosystems featuring ‘human stewardship’ (before the 1960s), that is, laaf aadaa seeraa to ‘ruined landscapes’ (after the 1960s), that is, laaf bade. Our interest is in understanding how the Borana perceive the impact of land use changes from these two conceptual perspectives. In group discussions, key informant interviews and household surveys across five of the nine well clusters, we found that the society described the changed tula cultural landscape in terms of drivers of well dynamics (i.e. use and disuse), break up of land use zonations, patterns of human settlement (traditional versus peri-urban), expansion of crop cultivation, and changes in environmental quality. Using the two concepts, we analysed linkages between changing patterns of land use that transformed the system from laaf aadaa seeraa, which ensured human stewardship, to laaf bade, which resulted in ruined landscapes. From these we analysed environmental narratives that showed how the society differentiated the past human stewardship that ensured sustainable landscape management from the present ruining of tula well cultural landscapes. 相似文献
15.
Geir Terje Eigestad Helge K. Dahle Bjarte Hellevang Fridtjof Riis Wenche Tjelta Johansen Erlend Øian 《Computational Geosciences》2009,13(4):435-450
The Johansen formation is a candidate site for large-scale CO2 storage offshore of the south-western coast of Norway. An overview of the geology for the Johansen formation and neighboring
geological formations is given, together with a discussion of issues for geological and geophysical modelling and integrated
fluid flow modelling. We further describe corresponding simulation models. Major issues to consider are capacity estimation
and processes that could potentially cause CO2 to leak out of the Johansen formation and into the formations above. Currently, these issues can only be investigated through
numerical simulation. We consider the effect of different boundary conditions, sensitivity with respect to vertical grid refinement
and permeability/transmisibility data, and the effect of residual gas saturations, since these strongly affect the CO2-plume distribution. The geological study of the Johansen formation is performed based on available seismic and well data.
Fluid simulations are performed using a commercial simulator capable of modelling CO2 flow and transport by simple manipulation of input files and data. We provide details for the data and the model, with a
particular focus on geology and geometry for the Johansen formation. The data set is made available for download online. 相似文献
16.
Concerns have been raised that near-term black carbon abatement strategies for global warming mitigation would interfere with the longer-term CO2 abatement efforts. In response, we put forward a “combined target and metric approach”, a theoretical framework, in which the time horizon of the metric is linked to the specific target of the climate policy. In this approach, a shorter time horizon for the metric is justified only when the overall climate policy is tightened; the lower the target level of the climate policy, the earlier the year of the target. Employing a consistent time perspective for the metric and target means that enhanced near-term reduction of short-lived climate forcers does not reduce the importance of the CO2 abatement, since the overall climate target is stricter. 相似文献
17.
Nathan Rive Asbjørn Torvanger Terje Berntsen Steffen Kallbekken 《Climatic change》2007,82(3-4):373-391
The question of appropriate timing and stringency of future greenhouse gas (GHG) emission reductions remains an issue in the
discussion of mitigation responses to the climate change problem. It has been argued that our near-term action should be guided
by a long-term vision for the climate, possibly a long-term temperature target. In this paper, we review proposals for long-term
climate targets to avoid ‘dangerous’ climate change. Using probability estimates of climate sensitivity from the literature,
we then generate probabilistic emissions scenarios that satisfy temperature targets of 2.0, 2.5, and 3.0°C above pre-industrial
levels with no overshoot. Our interest is in the implications of these targets on abatement requirements over the next 50 years.
If we allow global industrial GHG emissions to peak in 2025 at 14 GtCeq, and wish to achieve a 2.0°C target with at least
50% certainty, we find that the low sensitivity estimate in the literature suggests our industrial emissions must fall to
9 GtCeq by 2050: equal to the level in 2000. However, the average literature sensitivity estimate suggests the level must
be less than 2 GtCeq; and in the high sensitivity case, the target is simply unreachable unless we allow for overshoot. Our
results suggest that in light of the uncertainty in our knowledge of the climate sensitivity, a long-term temperature target
(such as the 2.0°C target proposed by the European Commission) can provide limited guidance to near-term mitigation requirements. 相似文献
18.
John Terje Staveland 《Marine pollution bulletin》1979,10(9):255-258
One year after an accidental spill of approx. 2000 t of Iranian crude oil on the west coast of Norway, specimens of the gastropod Littorina littorea were collected from the oil polluted shore and allowed to spawn in the laboratory. Snails were also collected from an unpolluted reference site. The oil contamination seemed to have no detectable effects on fertilization. However, the hatching success of the veliger larvae was significally less in the ‘oil polluted’ population. Some highly abnormal eggs were also observed in this egg population. 相似文献
19.
Facies model for a coarse‐grained,tide‐influenced delta: Gule Horn Formation (Early Jurassic), Jameson Land,Greenland 
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下载免费PDF全文 Christian Haug Eide John A. Howell Simon J. Buckley Allard W. Martinius Bjørn Terje Oftedal Gijs A. Henstra 《Sedimentology》2016,63(6):1474-1506
Tide‐dominated deltas have an inherently complex distribution of heterogeneities on several different scales and are less well‐understood than their wave‐dominated and river‐dominated counterparts. Depositional models of these environments are based on a small set of ancient examples and are, therefore, immature. The Early Jurassic Gule Horn Formation is particularly well‐exposed in extensive sea cliffs from which a 32 km long, 250 m high virtual outcrop model has been acquired using helicopter‐mounted light detection and ranging (LiDAR). This dataset, combined with a set of sedimentological logs, facilitates interpretation and measurement of depositional elements and tracing of stratigraphic surfaces over seismic‐scale distances. The aim of this article is to use this dataset to increase the understanding of depositional elements and lithologies in proximal, unconfined, tide‐dominated deltas from the delta plain to prodelta. Deposition occurred in a structurally controlled embayment, and immature sediments indicate proximity to the sediment source. The succession is tide dominated but contains evidence for strong fluvial influence and minor wave influence. Wave influence is more pronounced in transgressive intervals. Nine architectural elements have been identified, and their internal architecture and stratigraphical distribution has been investigated. The distal parts comprise prodelta, delta front and unconfined tidal bar deposits. The medial part is characterized by relatively narrow, amalgamated channel fills with fluid mud‐rich bases and sandier deposits upward, interpreted as distributary channels filled by tidal bars deposited near the turbidity maximum. The proximal parts of the studied system are dominated by sandy distributary channel and heterolithic tidal‐flat deposits. The sandbodies of the proximal tidal channels are several kilometres wide and wider than exposures in all cases. Parasequence boundaries are easily defined in the prodelta to delta‐front environments, but are difficult to trace into the more proximal deposits. This article illustrates the proximal to distal organization of facies in unconfined tide‐dominated deltas and shows how such environments react to relative sea‐level rise. 相似文献
20.
Jan S. Fuglestvedt Terje K. Berntsen Odd Godal Robert Sausen Keith P. Shine Tora Skodvin 《Climatic change》2003,58(3):267-331
In this paper, we review existing and alternative metrics of climate change, with particular emphasis on radiative forcing and global warming potentials (GWPs), in terms of their scientific performance. Radiative forcing is assessed in terms of questions such as the utility of the concept, uncertainties and sensitivity to key assumptions. The assessment of emission indices focuses on the climate and other resulting impacts (end points) against which emissions are weighted; the extent to which (and how) time dependence is included, with regard to both emission control and impact; how cost issues are dealt with; and the sensitivity of the metrics to various assumptions. It is concluded that the radiative forcing concept is a robust and useful metric of the potential climatic impact of various agents and that there are prospects for improvement by weighing different forcings according to their effectiveness. We also find that although the GWP concept is associated with serious shortcomings, it retains advantages over any of the proposed alternatives in terms of political feasibility. Alternative metrics, however, make a significant contribution to addressing important issues, and this contribution should be taken into account in the further development of refined metrics of climate change. 相似文献