摘要:

ABSTRACTStoröya is a 50 km2large island in northeastern Svalbard. Its southern half is covered by a cold-based ice cap, while the remaining part (22 km2) is non-glacierized. Most of the latter area is covered with regolith.The marine limit was found at 66 m a.s.l. Above this elevation the regolith has a non-washed character but still contains rounded boulders of the same type as below the marine limit. As many of these rounded boulders are made of metamorphic or red magmatic rocks found on Nordaustlandet, while the bedrock of Storöya is gabbro and quartz diorite, the regolith is considered to be old beach material transported as till to the island.Here and there bedrock crops up through the regolith. These rock exposures lack all glacial sculpture, wherefore the glacier that deposited the till on Storöya must have been cold-based. In analogy with presentday conditions on Austfonna-Sörfonna a warm-based interior of the glacier must have existed on Nordaustlandet.Eight samples of driftwood have been collected. The highest sample was taken from 53 m a.s.l. Extrapolation of the curve to the marine limit shows that deglaciation of Storöya started around 10 000 years B.P. on the northeastern tip of the main hill. The preceeding advance of a partly warm-based glacier from Nordaustlandet is suggested to have taken place during Younger Dryas.During the Holocene epoch Storöyjökulen must have had a smaller area than at present at least between 7200 and 3200 years B.P. and most probably also between 10000 and 7200 years B.P.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880069

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTOn several documented occasions water in moulins on Storglaciären has risen to a level such that, if a direct connection to the base of the glacier exists, water pressures there would have exceeded the ice overburden pressure. These events were accompanied by audible cracking, and in at least one case by an exceptional discharge of silt-laden water at the snout of the glacier. In one case the zone of high water pressure may have propagated down glacier with a speed of about 150 m·hr-1. In several respects the high water-pressure events on Storglaciären, a non-surging glacier, resemble the mini-surges of Variegated Glacier, Alaska, a surging glacier. If these high water pressure events are, in fact, mini-surges, it is significant that they occur on non-surging glaciers as well as on surging glaciers.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880070

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTThe connotation of the term rock glacier, has been one of a common origin form but it is increasingly apparent that we are studying a range of landforms which, with the exception of the glacier debris system type, have no relationship with glaciers. The approach to rock glaciers as a unique form is re-evaluated in the light of the vast numbers which occur in the southwest Yukon. The implications are that they are the norm not the unusual in the development of the proglacial landscape and that correctly identified will provide new evidence for post glaciation landscape evolution.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880071

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTModern glaciers in the cordillera west and east of the plain of Laguna Junín northeast of Lima are confined to small summits and west-facing cirques. Snowline today is at about 4900 m on the west and 4800 m on the east. That these small glaciers were larger in the recent past is indicated by small moraines and by areas nearly bare of vegetation peripheral to the present glacier limits.In the Pleistocene a mountain glacier complex covered most of the cordillera and spread to all but the center of the plain, thus damming Laguna Junín. Two phases of glaciation can be distinguished. The younger is marked by sharp moraines dotted with small depressions. The older has smooth landforms, no undrained depressions, and locally a thin cover of loess. Retreat from the younger moraines may not have commenced until about 12,000 years ago.Maximum late-Pleistocene snowline depression is calculated at about 300 m in the western cordillera and 500 m in the eastern, on the basis of the elevation of small cirque lakes. Snowline depression of 300 m could be caused by a depression in mean annual temperature of only 2°C. Greater snowline depression on the east may reflect the southward shift of the tropical rain zone in the Amazonian lowlands, as a secondary effect of the vast Laurentide ice sheet of North America.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880072

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTPrevious analysis has failed to establish unequivocally the genesis of englacial debris bands within the Glacier de Tsidjiore Nouve. Although extraglacial sources were presumed to be dominant, some of the debris appeared to be derived either from a subglacial source or had not been passively transported. Evidence obtained through the application of scanning electron microscopy reinforces the view that the englacial debris was incorporated within the glacier via crevasses in the firn basin, and indicates that it is derived from (1) supraglacial debris, resulting from subaerial weathering of rock-faces above the ice in the firn basin, and (2) subglacial debris derived from the base of ice standing above these rock faces. The results of this investigation demonstrate the value of scanning electron microscopy in the study and interpretation of complex sediment assemblages on and within glaciers.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880073

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTThe spatial correlation analysis of daily rainfall data for a 29 month period in the northern coastal area of Tanzania has revealed a definite trend of higher rainfall correlations parallel to the coastline than is apparent normal to it. The general distance-decay rate of correlation coefficients for daily rainfall approximates a semi-logarithmic form, but is different in the longshore and cross-shore directions. At the very small scale, using data from a dense network of rain-gauges in Dar es Salaam, the general trend is reversed, suggesting that cellular development of intense rainfall occurs within the general trend parallel to the coast. As a result higher correlation coefficients persist for a greater distance normal to the coast at this scale. The development of rainstorm activity along sea- and land-breeze fronts is suggested as a major contributing factor to the rainfall of the area.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880074

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTMeasurements of meander wavelength and cross-section scale, averaged on a reach basis, are related to estimates of the mean annual flood from eleven upland catchments. Results support the hydrological control of the scale of such coarse-bedload channels and these are discussed in comparison with relationships involving different types of channel. There is however, high variability about these mean conditions, and this is attributable to patterns of confinement imposed on upland channels and on variability on floodplain materials in this environment. Environmental influences are outlined at a reach and bend scale.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880075

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTAn assemblage of highly weathered bedrock forms is reported from an upland ridge at 500 m a.s.l. near Cory Glacier on the southeastern coast of Ellesmere Island. Examples of grus accumulations, tafoni, weathering pits and tors are described. The role of salt crystallization on the micro-fracturing process responsible for their formation is postulated on the basis of field observations and water chemistry data. This upland ridge has apparently undergone minimal stripping through the Wisconsin and may have been protected beneath cold based ice over much of that time.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880076

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTData on large rockslides presented in a book by Olafur Jónsson (1976) are analyzed in terms of their magnitude and frequency in the Postglacial (10 000 a BP). Size has been examined by division into four groups, the modal size is from 1 to 10×106 m3. Age of rockslide events was assessed by relative methods by O. Johnsson and is thought to be internally consistent. Five age categories have been used and the modal group (III≈3–5000 a BP) has 34 % of rockslides. The period 3–7000 a BP contains 60% of all events; less than 5% have occurred in the last 1000 years. Age-size distributions suggest that the smallest slides are also the youngest; the largest events are the oldest. Problems associated with interpretation of the data are discussed in terms of a probability model but it is concluded that only a very simple interpretation is possible by its use. Climatic controls are not considered to be of prime importance in determining either size or age of slides. The majority of slides are found in lavas (Quaternary or Tertiary) and it is concluded that cleft water pressure (in some cases as a result of waning ice sheets) is the prime cause of slope failure.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880077

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

ABSTRACTFan-shaped pediments up to almost 2 km2in area occur along the west and south piedmont slopes of Roan Mountain, North Carolina. Sediment mantles average less than 18.5 m in depth, and generally appear to be underlain by saprolite. Three ages of fan terraces were mapped, based on morphology and weathering characteristics. Results show that most terraces are unpaired and that the cross-fan sequence of terraces is either irregular or that younger terraces tend to abut valley walls. The terraces thus appear to be the result not of cyclic erosion and deposition produced by Quaternary climatic change, but of recurring stream capture and lateral erosion on the mountain piedmont. Climatic change may affect the fans, however, as relative-age dating (based on percent clay, Munsell hue, and weathering-rind thickness) at 80 sites provides some evidence for episodic deposition, but this effect probably play 5 only a minor role in sculpting the piedmont landscape. No absolute-age dates were obtained on deposits, but several lines of evidence based on weathering criteria suggest that the oldest fan terraces are at least several hundred thousand years old. The regression equation of fan area on drainage-basin area,At, =c And5. yields values ofc(0.38) andn(0.76) comparable to those reported for aridregion alluvial fans, suggesting that the size of the drainage basin can determine the amount of lateral erosion as well as the amount of deposition taking place on the piedmont.

ISSN:0435-3676    

DOI:10.1080/04353676.1983.11880078

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor