摘要:

ABSTRACTWith the help of numerous till fabric analyses and other glacial indicators obtained from the study area proper a scheme of ice-flow pattern and ice-thickness variation throughout Weichselian time is put forward which in many respects differs from earlier ones. In the two separate fell areas on the Finnish side of the study area there can be discerned a clear zonal arrangement in an assemblage of residual bedrock forms such as tors, kopjes and inselbergs. This can be linked with areally altering conditions in the ice sheet dynamics. The dependence of ice flows on existing local and regional relief during various glacial phases has been verified by means of quantitative comparisons between known ice movement directions and the effective orientation of the bedrock relief. In the light of results gained from a large number of minor and major test areas it seems clear that this dependence has changed considerably from phase to phase according to thermal conditions on the ice sheet base.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880269

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTThe nature and origin of the outermost‘Little Ice Age’moraine in front of a NE-flowing glacier (Storbreen. Jotunheimen) are investigated by analysing the variability along the length of the moraine of a range of characteristics (cross-profile form, surface composition, clast form and quartz sand grain characteristics). Concentrated application of a range of techniques in relation to a single moraine has enabled inferences to be made about glacial transport paths of debris in the moraine and processes of moraine-building. Moraine form is consistent within lateral and latero-terminal sections. Origin is attributed to a combination of some pushing of valley-side debris and dumping of glacially-transported material, in which the ratio of modified subglacial to unmodified supraglacial/englacial debris increases downglacier. A larger southern than northern side of the outer moraine is attributed to a difference in the quantity of debris being supplied from headwall areas, which are steep and heavily-eroded on the southern side but low-angled and vegetated on the northern side.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880270

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTThe altitudinal frequency distributions of cryoplanation terraces in four areas of Alaska approximate normal probability curves, reflecting an elevation-controlled climatic zone that is optimal for terrace development. The elevational coincidence of cryoplanation terraces and glacial cirques in central and western Alaska indicates that development of cryoplanation terraces requires altitudinal proximity to the climatic snowline in mountainous regions with continental climatic conditions, reinforcing the nivation hypothesis of terrace development. Because criteria used to define“lower limits”in traditional regionalizations of alpine periglacial phenomena are inherently unstable, it is preferable to base definitions of altitudinal zones on statistical measures of central tendency.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880271

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTParticle morphology and fabric were examined on three talus slopes with different aspects (SW, S, SE) at Lassen Peak, California, to analyze the spatial variability of clast characteristics and determine the geomorphic processes causing it. The slopes had concave profiles and a pronounced particle sorting by size and shape. Sorting was not gradual; instead, a basal fringe of clasts larger and more equidimensional than those on the talus above was identifiable with statistical tests. Particle fabrics were characterized by a subhorizontal girdle coincident with the local slope, dominant modes parallel or oblique to the slope, and a high percentage of imbricated clasts. The basal fringe and the fabrics were most pronounced in the SE and S taluses.The observed sedimentological patterns suggest that rockfall is the dominant agent of clast deposition. However, the fabrics indicate that many particles glide down the talus with their long axis parallel to the slope. This occurs commonly on the upper slopes, mostly covered by fine debris, but cannot take place on the blocky basal talus. A persistent snow cover on the SE and S flanks provides a smooth surface for particles, which are segregated by size and shape while descending. Large and spherical clasts reach the toe slope, forming a basal fringe, while small and flat stones stop on the upper talus. Other processes contributing to particle transport include miniature debris flows, dry debris slides, and needle-ice growth.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880272

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTSeventeen14C age determinations by accelerator mass spectrometry (AMS) have been carried out on individual fragments of marine shells from Nordaustlandet, Svalbard. Aside from a Holocene control sample only six of the shells, mainly from moraine ridges associated with present-day glaciers, are of Holocene age. The most interesting results are dates of 9180±130 years BP (Ua-672), 9525±130 years BP (Ua-905) and 9675±140 years BP (Ua-1058) on shell fragments from an interbobate moraine between Vestfonna and Sere Franklin- breen. The site is 6 km behind the calving front of Søre Franklinbreen.Six of the remaining eleven samples are>40 000 years old. A date from the same interlobate moraine between Søre Franklinbreen and Vestfonna gave 34 700±810 years (Ua-345), but it seems safest to regard this value as a minimum age also. The same is true of dates of 35 230±790 years (Ua-670) from till-like material within an area of raised beaches in Jäderinfjorden and 38 100±1070 years (Ua-673) from till-like material underlying beaches on Wargentinflya southwest of Lady Franklinfjorden. The dates indicate that several anomalous ages determined previously, six in the 13 000 to 23 000 year-range and one close to 30 000 years, are the result of mixing of Holocene-aged shells with old' shells. The results also show that at least two of the main outlet glaciers from Vestfonna were much reduced in size in early Holocene time.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880273

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTUp till now studies of basin parameters influencing runoff in West Africa have largely been confined to very small basins. For this study of 10 medium sized basins in Southeastern Nigeria, principal components analysis reduced 14 runoff, rainfall and physiographic indices to five orthogonal components, viz basin size, landuse, basin steepness, channel steepness, basin altitude, which together explain 88.4 percent of observed variance.Five component variables, viz basin area, percentage of basin area covered by forests, drainage density, dry season rainfall and channel slope are used in a regression which provides a prediction of annual runoff, with a coefficient of determination of 0.72.Explanations are suggested for the significance of these variables for runoff.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880274

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTMono-and stereoradiographs of sediment in rectangular coring tubes are used for core correlation and for quantifying contemporary variations in rates of sedimentation in Edsviken, a bay of the western Baltic Sea with annually laminated, modern deposits. Subsamples from one of the cores are used for evaluating the Pb-210 parameters and models in relation to the sedimentological conditions in the bay. The agreement between the X-ray results and the C.R.S. Pb-210 ages is good, although there is a major discrepancy between supported Pb-210 and Ra-226. Sediment focusing is the dominant explanation of the spatial variations in sedimentation rate in Edsviken Bay. The present rate of sedimentation in the deepest part of the bay is about three times higher than the average annual value for the bay, which amounts to 30 mg/cm2. About half of the present sediment accumulation in the bay is probably due to the sediment yield from the drainage area. This ought to be the main reason why the unsupported Pb-210 flux of the Edsviken Bay is found to be a factor of two higher than the average annual atmospheric flux of Scandinavia, 0.15±0.05 pCi/cm2.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880275

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTThe periglacial form group is well represented in the Norden countries. The latest identified form is the talusderived rock glacier. In geomorphological papers a feature designated as talus terrace, or talus moraine, was described, but the true permafrost origin was not recognized. By means of aerial photographs a mapping of rock glaciers has now started, both on the Scandinavian peninsula and in Spitsbergen which, hopefully, will form the base for systematic studies of the phenomenon.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880276

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTThe glacial chronology, obtained from proglacial lacustrine sediments, shows that Riukojietna, a small ice cap. disappeared or was small and inactive in the early-mid Holocene. A reactivation of the ice cap occurred around 2000 B.P. Riukojietna has retreated rapidly after a distinct maximum in extent in the beginning of the twentieth century. Measurements yielded negative net balances between 1985 and 1988. Differences in net balance seem to be caused primarily by fluctuating summer balances. Since Riukojietna has a relatively small vertical extent and is relatively low lying compared with cirque glaciers, it is much more sensitive to changes in the climate. Riukojietna is far from being in balance with the existing climate and will, if present trends continue, finally disappear.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880277

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

ABSTRACTFlarks are reported to occur in mires in Qathlamba (the Drakensberg Range) of the Maloti, Lesotho at an altitude of 3200 m a.s.1. Flarks are not previously reported from Africa. Conditions for the formation and maintenance of flarks are discussed. It is argued that local waterlogging is a more likely explanation for the formation of flarks in Qathlamba than frost action.

ISSN:0435-3676    

DOI:10.1080/04353676.1989.11880278

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor