摘要:

AbstractThe tongue of Mikkaglaciären was radio-echo sounded in May 1983. The results revealed a relatively thin ice cover (max 175 m) lying on a smooth, flat bed. With the use of these radio-echo data and data from Storglaciaren, the equipotentials at the bottom of the glaciers were calculated and the water-flow patterns thus predicted were compared with observations. Tracer experiments carried out by Stenborg on the two glaciers revealed flow patterns that are in good agreement with the equipotential field. The seasonal variation in the drainage pattern of Storglaciaren is herein attributed to changes in the pressure regime in the conduits during the melt season, as has been suggested by Hooke (1984). Differences in the bottom topography and flow dynamics, are believed to be the main causes for the difference in the drainage patterns between the two glaciers.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880233

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractThe basal ice sequences of two glaciers descending from the equatorial ice cap of El Cotopaxi, Ecuador, comprise several metres of debris-rich ice. Up to 4m of‘stratified’ice and debris are attributed to the freezing of basal meltwater to the glacier sole close to the margin. The thickness of this layer is related to the permeability of the sub-strate, which determines the meltwater supply at the margin. Debris bands up to 10cm thick in the basal sequence are attributed to thrusting induced by compressive flow.‘Dispersed facies’regelation ice is not present at the site, indicating that the basal environment in the interior is not one of stable pressure-melting/regelation conditions, but probably one of continuous melting. The entrainment and stacking of basal debris occurs over a very short distance, close to the margin.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880234

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractIn order to acquire information about the dynamics of internal movement of a rock glacier, the three-dimensional eigenvalue technique was applied to the fabric analysis of 13 samples of clasts from a vertical section in a 15 m deep trench in this landform on Mt. Mestas, Colorado, U.S.A. The eigenvalue analysis of dip and directional data from platy felsite clasts revealed that the mean direction of the clasts was oriented transverse to the downslope direction. A two-axis plot of the ratios of normalized eigenvalues illustrated that the fabric could be identified as strong clusters although weak girdles were also detected. By combining samples 1–6, 7–9, 10–13, respectively, and comparing their mean dip of the clasts relative to the surface angle reveals three trends. Two hypotheses were posed to explain the cyclic data: (1) three temporally, distinct, catastrophic debris flows contributed to the development of the rock glacier, and/or (2) the three groups of samples can be attributed to internal shear planes.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880235

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractNumerous ploughing blocks characterize the south-facing valley, north of the Finse railway station in South-Central Norway. The largest, 4,9 by 5,0 by 5,6 m, calculated to weigh about 36.400 kg, is the most conspicuous. Upslope is a 42,5 m linear depression; downslope is a type B mound, ploughed up by the block. It is proposed that greater thermal conductivity of the block causes earlier freezing beneath it, drawing water from adjacent sediment to the freezing front. Faster thawing of the higher water-content sediment in the spring allows squeezing of mud from beneath the block, which then slides preferentially downslope into the space vacated by the mud. With this area first having been ice-free c. 9000 yrs B.P., the average minimum rate of movement over this 18°slope has been about 0,5 cm/yr. The Finse block is the largest ploughing block and has the longest trough of any known to date.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880236

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractAn uncommon type of narrow till ridge occurring within a limited area in the southern Swedish mountains is examined. The ridges are located high on gentle mountains slopes and usually have a very orderly appearance, with zig-zag patterns and straight sections. Excavations in two ridge systems revealed a homogenous till without sorted material or sedimentary structures. The stratigraphy and morphology indicate that the ridges were created by squeezing of till into subglacial voids, at some localities most likely related to subglacial drainage networks. The ridges have no clear relationships to deglaciation landforms in the area. At one locality some ridges are partially destroyed by fluting interpreted to predate the deglaciation phase. One possible explanation for the preservation of the ridges is that they were created before the last phase of deglaciation and were preserved under cold-based ice.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880237

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTThe paper describes a study of the changes in grain-size parameters associated with erosion and deposition on a microtidal flat. Preliminary results suggested that over 11 years the sediment became finer in areas of erosion and coarser in areas of deposition. Closer study revealed that these results primarily reflected the time of sampling: seasonal variations were found to be greater than the long-term changes. An exception was found in an area with rapidly spreading vegetation and consequent high rates of sedimentation. Here long term changes exceeded seasonal changes. Bed load samples, sampled in traps, changed much more than samples taken on the surface. This was particularly the case during a period, in which spill from sand dredging in the navigation channel caused high rates of sediment transport on the micro-tidal flat. Hyperbolic grain-size parameters were found to give much better environmental discrimination than traditional percentile based parameters.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880238

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTNearshore bar morphology has been studied in a low energy, short period-wave environment. The modal beach state was the Rhythmic Bar-and-Beach, characterized by the presence of crescentic bars and megacusps. This beach state is also the most frequently occurring state along moderate to high- energy coasts in southeastern Australia. The reasons for the morphological similarities in these very different coastal environments have been investigated and it was found that morphology at the low-energy site to a large degree was influenced by sporadically occurring storms. During the periods between storms, the morphology was more or less arrested.Tentatively suggested wave height threshold conditions for the initiation of a given beach state were compared with results reported from southeastern Australia (Short 1980) and it was found that these threshold values were significantly different, probably owing to the finer sediment grain sizes and steeper waves at the low-energy site.Finally,Ω= Hb/wsT and 30-day weighted mean (Ω30) have been computed. A somewhat improved weighted mean expression is proposed for this locality. Values were approximately twice as large as results reported from southeastern Australia.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880239

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTThe shorelines of the so-called Heby esker (also called Dalkarls-åsen and Hedesundaåsen—ås being Swedish for esker) were levelled. The results are presented both as sections and as distance diagrams. It was assumed that the more continuous shorelines were formed during eustatic transgression in early Litorina times and earlier stages in the development of the Baltic Sea; although no dating attempts have been made. The stratification of the shore marks does not immediately make the continuous shorelines come out. However, one attempt to stratify shore-elements that were considered continuous turned out to be statistically significant as far as the south to north inclination of the elements was concerned. By subjective stratification of the other shore elements it appeared, that even these elements showed a similar percentual inclination. Naturally, this inclination must indicate an increasing shore displacement or land uplift towards the north. However, this increase was found to be much smaller the what could be deducted from previous studies.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880240

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTSediment yield data were collected from national institutes and other sources. Attention was paid to data reliability in general. The global pattern of variation in net erosion is shown in a separate map.Sediment yield is affected by many factors such as climate, relief, soil, vegetation, and human influence. Tectonic instability and volcanic activity are also of importance. Climate is one of the major factors controlling net erosion rates and is chosen as a basis for division in statistical analysis. Sediment yields are very high in the‘Af’climatic group, i.e. tropical humid climate without a dry period. Contrary to what was expected, tropical climates with a dry season do not show values as high as in the‘Af’group. Warm temperate climates with a dry season,‘Cs’and‘Cwa’climates, exhibit high sediment yields. Among the warm temperate climates without a dry period, Cfa climates have few rivers with low sediment yield whereas Cfb climates have many rivers with low yield. Boreal climates (cold temperate climates) contain rivers, most of which have low values except for some Chinese data in Dwa and Dwb climates. In boreal climates within another climatic zone, but being boreal as a consequence of altitude,‘Ds’and 'Df, sediment yields are usually higher than in the zonal boreal climates.Runoff has been used as a variable representing climatic conditions. Relationships between runoff and sediment yield are shown in diagrams for different climatic groups. As there are different relationships or the lack of a relationship between runoff and sediment yield in the different climatic groups, there is no universal statistically significant global correlation between runoff and sediment yield which is valid for all climates.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880241

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

ABSTRACTThis paper examines the entire drainage basin of the Pite River, Swedish Lapland, but emphasis is placed on analyzing the morphology of the valley upstream of Benbrytar-forsen Rapids, some 100 km from the coast of the Gulf of Bothnia. In particular a comparison is made between the late glacial river system and the present-day Pite River, and details of both river systems are presented in map form. On morphological grounds the Pite River valley is divided into four segments. These are: 1. the valley within the high mountain region, 2. the valley within the premontane region, 3. the interior area above the highest late glacial shoreline, and 4. the valley below the highest late glacial shoreline. In order to emphasize the differences between the Pite River today and the glaciofluvial drainage network, four key sections of the upper river valley are described: Kaskaure/Låddaure, Kouddujaure/Falehaure, Apmo, and Bådakatj. The last mentioned site, the largest boulder delta complex in Sweden, has been discussed in three previous reports as well.

ISSN:0435-3676    

DOI:10.1080/04353676.1988.11880242

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor