Cenozoic uplift of Fennoscandia inferred from a study of the mid-Norwegian margin     

Liv M. Stuevold  Olav Eldholm 《Global and Planetary Change》1996,12(1-4)

Studies of the mid-Norwegian margin reveal that the Fennoscandian continental uplift represents a flexural intraplate deformation event separated in time and space from the regional syn-rift uplift associated with crustal breakup at the Plaeocene-Eocene transition. In the area 64–68°N, the uplift occurred from late Oligocene through Pliocene. During Late Pliocene and Pleistocene times the tectonic uplift was amplified by isostatic rebound in response to the Northern Hemisphere glaciation. The tectonic uplift component reaches 1 km in the northern part of the study area decreasing to the south. The shelf stratigraphy and sediment composition record the combined effects of tectonic uplift, eustatic sea level changes and Neogene climatic deterioration. The coeval uplift and climatic change may suggest causal relations. The resulting depositional model has three stages: (1) late Miocene ( 10.5-5.5 m.y.) increased continental erosion and deposition of prograding wedges most of which were later removed; (2) early-middle Pliocene (5.5-2.6 m.y.) development of extensive local ice-sheets reaching the coastline and deposition of the prominent, oldest Pliocene wedges; (3) Northern Hemisphere glaciation (2.6-0.01 m.y.) resulting in the younger wedges farther west covered by Quaternary deposits. The model is consistent with the development of landforms on the adjacent mainland. Both the tectonic and isostatic components of the Fennoscandian uplift appear to vary in magnitude along the uplift axis, however separation of the syn-rift plate boundary related uplift and the intraplate event support the Neogene age of the main Fennoscandian uplift. We document a correspondence between structural and physiographic margin segmentation and uplift magnitude and suggest that the intraplate deformation has a thermal origin. A hot-cold asthenosphere boundary beneath the Caledonide-Baltic Shield transition combined with pre-Tertiary relief at the base of the lithosphere might induce small-scale convection and preferential volume expansion beneath the observed elongate uplift.  相似文献   

A comparison of spicules in the Hα and HeII (304 Å) lines     

Olav Kjeldseth Moe  Oddbjorn Engvold  Jacques Maurice Beckers 《Solar physics》1975,40(1):65-68

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Benthonic foraminifera as indicators of the paleoposition of the Subarctic Convergence in the Norwegian-Greenland Sea     

Hans-Petter Sejrup  Hans Holtedahl  Olav Norvik  Ivar Miljeteig 《Boreas: An International Journal of Quaternary Research》1980,9(3):203-207

A method is presented for correlating benthonic foraminiferal communities in Late Quaternary marine sediments on continental shelves and in coastal areas with the planktonic foraminiferal stratigraphy of the North Atlantic and Norwegian Sea deep-sea sediments.  相似文献   

Landslide inventory in a rugged forested watershed: a comparison between air-photo and field survey data   总被引：2，自引：0，他引：2  

Francesco Brardinoni  Olav Slaymaker  Marwan A. Hassan   《Geomorphology》2003,54(3-4):179-196

Landslide inventories are routinely compiled by means of aerial photo interpretation (API). When examining photo pairs, the forest canopy (notably in old-growth forest) hides a population of “not visible” landslides. In the present study, we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the Capilano basin, coastal British Columbia. API was coupled with intensive fieldwork for identification and measurement of all landslides. A 30-year framework was adopted. We show that “not visible” landslides can represent up to 85% of the total number of failures and account for 30% of the volume of debris mobilised. Such percentages display high sub-basin variability with rates of sediment production varying by one order of magnitude between two sub-basins of the study area. This is explained qualitatively by GIS-based analysis of slope frequency distributions, drainage density, and spatial distribution of surficial materials. Such observations find further support in the definitions of transport-limited and supply-limited basins. As a practical consideration to land managers, we envisage that supplementary fieldwork for landslide identification is mandatory in transport-limited systems only. Fieldwork has demonstrated that gully-related failures have a greater importance than one could expect from API.  相似文献   

Advances in Holocene mountain geomorphology inspired by sediment budget methodology     

Olav Slaymaker  Catherine Souch  Brian Menounos  Gabriel Filippelli 《Geomorphology》2003,55(1-4):305

The sediment budget, which links sediment sources to sediment sinks with hydroclimatic and weathering processes mediating the response, is applied to the analysis of sediments in three alpine lakes in British Columbia. We provide two ways of using the sediment budget as an integrating device in the interpretation of mountain geomorphology. These approaches differ in their resolution and ability to budget the major components of the fine-sediment cascade in glaciated environments. Taken together, they provide an integrated index of landscape change over the Holocene. The first example compares the hydroclimatic controls of lake sedimentation for the last 600 years (A.D. 1370–1998) preserved in varved sediments from two of the lake basins. This hydroclimatological approach incorporates contemporary monitoring, air photo analysis, and detailed stratigraphy of sedimentation events within a single varve to infer the timing, sources, and preferred pathways of fine-grained sediments reaching the lake basins. The results indicate that glaciers, hillslope, and channel instability within the major subbasins are the principal sediment sources to the lake basins. Transitory sediment storage of glacially derived sediments within the channels is believed to modulate the episodic and more frequent delivery of sediments from adjacent hillslope and fluvial storage sites and direct routing of glacial rock flour during years of prolonged glacial melt. The second example, relying on the phosphorus geochemistry of sediments in an alpine lake basin, considers the evolution of phosphorus forms (from mineral to occluded and organic fractions) as a function of the soil development, inherent slope instability, and repeated cycles of glaciation and neoglaciation over the Holocene. This geochemical approach demonstrates that both neoglaciation and full glaciation have essentially zeroed the system in such a way that a high proportion of mineral phosphorus remains in the present lake sediments and the bioavailability of phosphorus (a key to ecosystem development) is low. Both examples illustrate the importance of variable sediment sources; the seasonality, frequency, and magnitude of sediment transfers; and the profound influence of ice cover over contemporary, neoglacial and Pleistocene time scales. They also signal the value of including both clastic and dissolved components in the sediment budget.  相似文献   

Geomorphology. A systematic analysis of late cenozoic landforms,A. L. Bloom,Prentice-Hall,Englewood Cliffs, 1978. No. of pages: 510     

Olav Slaymaker 《地球表面变化过程与地形》1979,4(3):297-298

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Geological events during the early formation of a passive margin     

Olav Eldholm  Eirik Sundvor   《Tectonophysics》1979,59(1-4)

The concept of plate tectonics implies that the normal sea floor spreading stage is preceded by a sequence of events associated with the break-up of continental crust. Thus, evidence of the early development of “non-failed” rifts is to be found at passive continental margins. Of special interest is the question of the extent of the continental crust and the structural and compositional changes associated with the change in crustal type. In addressing these topics, we have focused attention on the Norwegian margin between the Jan Mayen and Senja fracture zones (66°–70°N) in an attempt to understand its history of rifting and early sea floor spreading. p ]The southern part of this rifted margin is characterized by a wide shelf and the marginal Vøring Plateau interrupts a gentle slope at a level of about 1500 m. However, the margin becomes progressively narrower towards the north and a typical narrow shelf and steep slope emerge off the Lofo—tenVesterålen Islands (Fig. 1). In a reconstructed pre-opening configuration (Talwani and Eldholm, 1977) the narrowest part of the juxtaposed EastGreenland margin is found in the south and a wide shelf and slope corresponds to the Lofoten-Vesterålen margin.The most prominent structural element is a buried basement high underneath the Vøring Plateau. The high is bounded landward by the Vøring Plateau Escarpment, a major structural boundary which defines typical changes in the geophysical parameters. These are: (1) a sudden increase of depth to acoustic basement; (2) changes in the velocity-depth function; (3) a gravity gradient; and (4) a magnetic edge anomaly separating sea-floor spreading type anomalies from a quiet zone on the landward side (Talwani and Eldholm, 1972). These observations were interpreted in terms of a sharp ocea—ncontinent crustal transition along the escarpment with sea-floor spreading commencing between anomaly 24 and 25 time (56–58 m.y. B.P.). Alternatively, the concept of ancient oceanic crust landward of this escarpment and the possible existence of continental crust under the outer basement high have been argued and we refer to Eldholm et al. (1979) for a detailed discussion.  相似文献   

A generalized theory for line formation in a homogeneous magnetic field     

Olav Kjeldseth Moe 《Solar physics》1968,4(3):267-285

The formation of spectral lines in a homogeneous magnetic field has been studied. A new method for solving the transfer equations for polarized light has been found. Using this method, the Stokes parameters may be derived without any special assumptions regarding the model atmosphere. With the line formed by pure absorption, the expressions for the Stokes parameters may easily be adapted to numerical calculations. In order to illustrate the method, the line profile for the Zeeman triplet 5250 has been calculated using a photospheric model atmosphere.  相似文献   

Key site variables governing the functional characteristics of Dissolved Natural Organic Matter (DNOM) in Nordic forested catchments   总被引：1，自引：0，他引：1  

Rolf D. Vogt  Jarkko Akkanen  Dag Olav Andersen  Rainer Brüggemann  Bimal Chatterjee  Egil Gjessing  Jussi V. K. Kukkonen  Håkon E. Larsen  Jörg Luster  Andrea Paul  Stephan Pflugmacher  Mike Starr  Christian E. W. Steinberg  Philippe Schmitt-Kopplin  Ádám Zsolnay 《Aquatic Sciences - Research Across Boundaries》2004,66(2):195-210

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Data laundering leading to meaningful principal component classification criterion and map attribute in surface geochemistry     

Olav H. J. Christie 《Aquatic Sciences - Research Across Boundaries》1995,57(3):242-254

Principal components classification based on geochemical data from sea bed samples offers a discriminant methodology for assignment of sea bed core location to defined types of hydrocarbon seep characteristics. Significant contributions to the geochemical fingerprint of the samples, like influence of sediment nature and biogenic input, are considered bias effects by oil explorationists and may be removed by aid of the method of principal components target rotation. This removal is called data laundering, and map attributes representing known hydrocarbon accumulations can be constructed from laundered data sets. Signatures of the Draugen (Haltenbanken, Norway) sea bed type occur over the Heidrun and Smørbukk fields and points out regions of interest to exploration in unexplored areas.  相似文献