Developing a modern pollen–climate calibration data set for Norway     

ANNE E. BJUNE  H. JOHN B. BIRKS  SYLVIA M. PEGLAR  ARVID ODLAND 《Boreas: An International Journal of Quaternary Research》2010,39(4):674-688

Bjune, A. E., Birks, H. J. B., Peglar, S. M. & Odland, A. 2010: Developing a modern pollen–climate calibration data set for Norway. Boreas, Vol. 39, pp. 674–688. 10.1111/j.1502‐3885.2010.00158.x. ISSN 0300‐9483. Modern pollen–climate data sets consisting of modern pollen assemblages and modern climate data (mean July temperature and mean annual precipitation) have been developed for Norway based on 191 lakes and 321 lakes. The original 191‐lake data set was designed to optimize the distribution of the lakes sampled along the mean July temperature gradient, thereby fulfilling one of the most critical assumptions of weighted‐averaging regression and calibration and its relative, weighted‐averaging partial least‐squares regression. A further 130 surface samples of comparable taphonomy, taxonomic detail and analyst became available as a result of other projects. These 130 samples, all from new lakes, were added to the 191‐lake data set to create the 321‐lake data set. The collection and construction of these data sets are outlined. Numerical analyses involving generalized linear modelling, constrained ordination techniques, weighted‐averaging partial least‐squares regression, and two different cross‐validation procedures are used to asses the effects of increasing the size of the calibration data set from 191 to 321 lakes. The two data sets are used to reconstruct mean July temperature and mean annual precipitation for a Holocene site in northwest Norway and a Lateglacial site in west‐central Norway. Overall, little is to be gained by increasing the modern data set beyond about 200 lakes in terms of modern model performance statistics, but the down‐core reconstructions show less between‐sample variability and are thus potentially more plausible and realistic when based on the 321‐lake data set.  相似文献   

Late Weichselian deglaciation and paleoenvironment of the shelf and coastal areas of Troms, north Norway - a review     

TORE O. VORREN  ARVID ELVSBORG 《Boreas: An International Journal of Quaternary Research》1979,8(2):247-253

The present knowledge of the Late Weichselian marginal moraines and paleoenvironment from the coastal and shelf areas of Troms and west Finnmark is reviewed. Diverse opinions exist regarding the position and age of the marginal moraines in the offshore areas.  相似文献   

The ability of debris, heavily freighted with coarse clastic materials, to flow on gentle slopes   总被引：2，自引：0，他引：2  

JAMES D. RODINE  ARVID M. JOHNSON 《Sedimentology》1976,23(2):213-234

Observations of many debris-flow deposits on gently-sloping alluvial fans have disclosed that debris commonly is heavily loaded with coarse clastic material and contains large isolated blocks. The paper describes how debris charged with coarse granular material can transport large blocks, yet flow on gentle slopes. Experimental results of mixing sand-sized particles with a slurry of clay plus water indicate that 45–55 vol. % of a single size, and up to 64% of two selected sizes, can be added before interlocking occurs. Theoretical analysis of multi-size classes suggest that 89 to more than 95 vol. % debris can be clastic materials without significant particle interlocking. The clay fraction, even if minor, plays a critical role in determining strength properties of debris. The mixture of clay plus water provides a cohesive slurry that supports fine-grained particles within the debris, as well as reduces the effective normal stresses between the particles. The increased unit weight of the clay plus water plus fine-grained particles allows the support of coarser grained particles. The pyramiding upon the clay-water slurry continues until the entire debris mass is supported in a virtually frictionless position because of the reduced effective normal stress and the lack of particle interlocking. Thus, the ability of debris flows to support large blocks can be understood in terms of the high unit weight of the displaced debris plus the strength of the fluid phase; that is, the blocks float in the debris as a result of a small density difference between the blocks and the debris, plus the cohesive strength of the clay-water slurry. Also, the ability of coarse clastic debris to flow on gentle slopes probably is a result of poor sorting of debris-flow materials which contain minor amounts of clay. The poor sorting allows the debris to have a high density yet have essentially no interlocking of clasts. The high density of the debris reduces effective normal stresses between clasts, thereby reducing apparent friction of the mixture.  相似文献   

Askeladden Delta Sequence (Palaeocene) on Spitsbergen—sedimentation and controls on delta formation     

ARVID NøTTVEDT 《Polar research》1985,3(1):21-48

Because of its coal potential the basal Tertiary Firkanten Formation on Spitsbergen has received much attention. The formation is an offset stacked (overall transgressive) sequence comprising at least eight coastaVdeltaic units each of which has a regressive character and is 10 to 30 m thick. The lowermost coal-bearing unit (Todalen Member) represents deltas which were largely fluvial-and tide-dominated while the upper unit deltas (Endalen Member) were wave-dominated. One of the transitional deltaic units, the Askeladden Sequence, has been examined in some detail along depositional dip (–15 km) and strike (–55 km). This unit represents wave-(tide)dominated delta conditions, and two main facies associations are recognized:

• Delta front/shoreline deposits (Facies Association I).

• Delta plain/coastal plain deposits (Facies Association II).

Askeladden sequence accumulated in a shallow, low-gradient embayment (Nordenskiold Land sub-basin) open to the south and southwest. Periodic, strong longshore currents caused a net northwards transport of sediment. Tidal range is considered close to the micro/meso-tidal boundary, and estimates of ancient wave regime indicate overall moderate wave conditions, suggesting that the extensive wave-reworking of the delta front/shoreline sands is related to relatively slow rates of fluvial input. Climate and tectonics are considered important contributory controls on sedimentation.  相似文献