摘要:

AbstractSystematic transect and grid surveys of ventifact presence/absence were made in order to assess palaeo‐ventifact abundance/distribution through Denmark and southern Sweden. The transects reveal a continuous ventifact distribution from western Denmark to south‐central Sweden giving evidence for the existence of significant palaeo‐wind action in extensive areas previously thought lacking in such evidence. Based on ice recession dates and vegetation development, ventifact formation is interpreted as having occurred mainly contemporaneously with the receeding Weichselian ice‐sheet. A grid survey in Scania, southern Sweden, demonstrates a continuous ventifact distribution irrespective of surface materials and topography. The ventifact occurrence outside areas with sandy soils indicates that suspended particles were effective abrading agents. Stable ventifacts confirm previous observations of easterly wind abrasion in Scania and exhibit an extremely small directional variability within, and between, sites. Ventifacts in southern Scandinavia are probably more indicative of transitory paraglacial conditions than periglacial conditions

ISSN:1045-6740    

DOI:10.1002/ppp.3430060302

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractNot all places may in fact warm under global change scenarios. This paper presents an example of climatic cooling from northern Quebec, Canada. Ground temperature measurements along the southern shore of Hudson Strait, northern Quebec indicate a cooling trend over the last seven years (1987‐93). Long‐term air temperature records show that this area has actually experienced continuous cooling for more than 40 years. Related studies suggest that the cooling is likely to continue due to freshening of subpolar water in the North Atlantic and Labrador Sea area. A one‐dimensional geothermal model was used to simulate the effect of continued cooling on permafrost thermal regime in Salluit, northern Quebec. The results show that, if the climatic trend continues for the next 50 years, the thickness of the active layer would decrease by 30cm (from 2.3 to 2.0 m) in gneiss and by 20cm (from 1.3 to 1.1 m) in till. Permafrost temperature at 20 m depth would decrease by 0.65 °C. Under the cooling scenario, rate of permafrost creep and slope activities would be reduced. Ice‐wedge regrowth would continue, and the buried ice wedges may even become reactivated. The results also indicate that regional snow precipitation data cannot be used directly in predicting ground thermal

ISSN:1045-6740    

DOI:10.1002/ppp.3430060303

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractStratified slope‐waste deposits are widespread in central Italy, even at elevations close to the present coastline. They are evidence of the cold climatic conditions which affected the area during the cold stages of the Upper Pleistocene. Their occurrence was strongly influenced by bedrock lithology (they are common on slopes composed of micritic and marly limestone). Detailed morphostratigraphic analysis and14C dating of alluvial and inter‐fingered slope‐waste deposits in a mountain area of the Umbria‐Marche Apennine (Upper Esino River basin) allows an outline of the chronological sequence of debris depositional phases during the Late Pleistocene. A few dates were also obtained from the Ponte di Crispiero sequence (in the contiguous Potenza River basin), which may be considered as a type section for the Late Pleistocene of Central Italy, Adriatic side. The stratified slope‐waste deposits were deposited after 50,000 to 60,000 years BP, in the Stadials of the Middle and Upper Pleniglacial. During the Interstadials, most of the slopes of the basin were colonized by steppe vegetation and the production of stratified debris was probaby restricted to the highest elevations. Increased rates of debris deposition occurred during the Upper Ple

ISSN:1045-6740    

DOI:10.1002/ppp.3430060304

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper reviews the literature on cold‐adapted micro‐organisms which might exist in ice and permafrost. Properly identified, microbial markers in the cryolithozone could be used in palaeoenvironmental reconstructions, in distinguishing between epigenetic and syngenetic depositional sequences, and in the recognition of secondary thaw unconformities. Cryobiological problems include (1) whether the bacteria are dead, dormant or in the active state, and (2) what factors determine the preservation of cell structures. A possible consequence of permafrost thawing, based upon predicted global warming scenarios, is that there may be an increase in microbial activity and an increase in active layer thickn

ISSN:1045-6740    

DOI:10.1002/ppp.3430060305

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the Albanian Alps, above 1700 m a.s.1., sixteen inactive rock glaciers have been identified, all colonized by herbaceous vegetation. Assuming a −2°C isotherm for the activity of rock glaciers, and after calculating the atmospheric lapse rate, it is estimated that thermal conditions must have been 6.4°C lower than the present mean annual temperature. Because rock glaciers occupied surfaces covered by ice during the periglacial Würm period, they cannot be older than 14,000‐17,000 years; so they are probably referable to the Dryas. Such a temperature drop took place probably during the

ISSN:1045-6740    

DOI:10.1002/ppp.3430060306

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCertain processes occurring in the northern part of the permafrost zone pose hazards for construction. These include cryogenic landslides. Three types are discussed for the Yamal Peninsula: shearing slides (active layer detachment failures), ground ice slumps, and earth flows. The first prevail in size and number.

ISSN:1045-6740    

DOI:10.1002/ppp.3430060307

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractGelifluction in the periglacial zone of the Tianshan Mountains occurs at 2500‐3600 m above sea level on north‐facing slopes. Abundant groundwater, fine grained sediments and slopes 10°‐30° favour gelifluction. Most gelifluction forms are lobate, a few are tongue‐shaped. The mean surface rate of movement is 11.14cm/a; the front advancing rate is 1.86cm/a. The moving rate in the middle part is greater than at the sides of gelifluction lobes, the mean rates being 3.1 cm/a and 0.86cm/a, res

ISSN:1045-6740    

DOI:10.1002/ppp.3430060308

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe cryostratigraphy of Holocene ice wedges is described from Western Siberia, Yakutia and the Trans‐Baikal region.14C dating and oxygen isotope determinations suggest that some of these wedges grew syngenetically during the Holocene climatic optimum. Inferred mean winter and mean January air temperatures for this period are presente

ISSN:1045-6740    

DOI:10.1002/ppp.3430060309

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1045-6740    

DOI:10.1002/ppp.3430060310

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY