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Kevin Kiernan 《The Australian geographer》1990,21(2):113-125
The Mt Anne massif is characterised by spectacular erosional landforms of glacial origin. Evidence of at least two separate Pleistocene glaciations is preserved in valleys that extend east and south of the massif, and also on nearby Schnells Ridge. There is evidence of a much older glaciation beneath the western slopes of the Mt Anne massif. Dense vegetation in the eastern valleys has inhibited mapping of the Quaternary geology there. These glaciations have influenced postglacial evolution of the landscape, including the advent of prominent karst features and Holocene landslip activity. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):169-170
The central Glomdal caves, Storbekkgrotta and Kalkrastgrotta, are found within a 30 m (approximately) thick band of white marble. The karst system is allogenic and the cave morphology and surface topography provide evidence of several phases of development: 1. Phreatic conduit development. 2. Drainage and vadose incision. 3. Partial or complete infill with clastic (glaciogenic) sediments. 4. Glacial truncation of the conduits. 5. Reversed, phreatic flow in the up-hill direction, producing paragenetic halftubes and rock pendants. 6. Partial outwash of the previous infilling sediment. 7. Holocene vadose invasion. Since the paragenetic features are superimposed onto vadose features, the reversed flow must have occurred after base-level (i.e. bedrock) lowering. Together with the topographical situation of the karst, phase 5 (paragenesis under reversed flow) may be explained by subglacial water flow. This implies a temperate glacier sole at a time when the icefield could over-ride the local valley topography and provide an up-hill directed englacial hydraulic gradient. The results suggest that sub-glacial water flow may utilize pre-existing karst conduits (which are extremely stable Nye-channels in the glaciohydrologic context) and enlarge them somewhat. It is still not proven that entire cave passages with radii of 1 to 2 m may form under such sub-glacial conditions, as suggested by Horn in 1947. The chemistry and conduit hydrology of deep sub-glacial waters are crucial parameters in this regard. 相似文献
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极地冰盖/冰川底部微生物的生命形态特征及其适应机制研究是当前最前沿的方向之一。越来越多的研究表明: 极地冰盖/冰川底部存在液态水和有机质, 可以为微生物生存提供生境。此外, 微生物参与冰盖/冰川底部地球化学风化过程, 对受气候变化驱使的环境变化尤为敏感。围绕着极地冰川底部微生物多样性及其对气候变化响应的研究主题, 重点介绍极地冰川底部微生物的生命形态特征、可能来源、所参与的地球化学反应机制以及与C、N循环的相互作用。旨在为未来关于冰川底部的研究提供参考。 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):151-156
The climatic variation of the Pleistocene acted on karst terrains to change the conditions of cave development. These changes were the result of three major effects: Ice Contact Effects, Ice Proximity Effects and Global Effects. Ice Contact Effects involve ice directly, producing glacial quarrying, sediment redistribution, water budget alteration, isostatic rebound, temperature controlled weathering, geochemistry changes, and hydraulic conditions. Ice Proximity Effects work at a distance from glacial ice, and include periglacial conditions, aggradation by outwash, loess deposition and disruption of master streams. Global Effects work over all planet areas and involve custatic sea level change and variation in precipitation. 相似文献
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The early Russian researchers working in central Siberia seem to have preferred scenarios in which glaciations, in accordance with the classical glaciological concept, originated in the mountains. However, during the last 30 years or so the interest in the glacial history of the region has concentrated on ice sheets spreading from the Kara Sea shelf. There, they could have originated from ice caps formed on areas that, for eustatic reasons, became dry land during global glacial maximum periods, or from grounded ice shelves. Such ice sheets have been shown to repeatedly inundate much of the Taymyr Peninsula from the north-west. However, work on westernmost Taymyr has now also documented glaciations coming from inland. On at least two occasions, with the latest one dated to the Saale glaciation (marine isotope stage 6 [MIS 6]), warm-based, bedrock-sculpturing glaciers originating in the Byrranga Mountains, and in the hills west of the range, expanded westwards, and at least once did such glaciers, after moving 50–60 km or more over the present land areas, cross today's Kara Sea coastline. The last major glaciation affecting south-western Taymyr did, however, come from the Kara Sea shelf. According to optically stimulated luminescence dates, this was during the Early or Middle Weichselian (MIS 5 or 4), and was most probably not later than 70 Kya. South-western Taymyr was not extensively glaciated during the last global glacial maximum ca. 20 Kya, although local cold-based ice caps may have existed. 相似文献
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Marissa H. Kelly Alison M. Anders Sara Gran Mitchell 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):147-159
We explore the relationships amongst bedding dip, basin aspect, and glacial landforms using field observations and GIS analyses of the northwestern Uinta Mountains of Utah. We examine basins on opposing sides of three ice divides in which quartzite beds of the Mount Watson Formation maintain a near constant dip. These areas provide contrasting relationships between ice flow and bedding dip directions while holding rock type and climate constant. We map the occurrence of three glacial erosional landforms: cliffs showing evidence of quarrying, scoured surfaces polished by abrasion, and overdeepenings. Cliffs and overdeepenings are more common in basins where bedding dips up‐basin, while scoured surfaces are more prevalent where bedding dips down‐basin. The significance of jointing in controlling glacial erosional forms is well established and we propose that bedding, as well as joints, dictates the geometry of quarried blocks and influences the spatial patterns of process dominance. Where bedding dips up‐basin, the geometry of pre‐existing weaknesses favours quarrying creating both cliffs and overdeepenings. In contrast, where bedding dips down‐basin, block geometry does not favour the creation of overdeepenings via quarrying and exposed bedding planes are subjected to glacial abrasion, producing scoured surfaces. 相似文献
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本文从天山冰川数量，冰储量、类型以及分布特征等方面系统地分析了天山冰川的资源及其分布规律，为经济建设提供可靠的山地水资源论据。 相似文献
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Basal shear stress and sediment strength associated with the development of glacial flutes exposed during the 20th century in the Saskatchewan Glacier Valley Alberta, Canada, were determined by comparing reconstructed ice thicknesses, basal shear stresses, and field properties of sediments with the morphologically similar Kiwa Glacier Valley, British Columbia, Canada, where flutes are absent. Reconstructed subglacial conditions in these two valleys were compared to understand why flutes were developed in the former and not the latter. Using an existing topographic map of each glacier, equations for a series of longitudinal profile lines were determined to represent the existing ice surface. A previous ice surface, identified by trimlines along the valley walls, was reconstructed by applying the equations of longitudinal profile lines from the existing ice surface to a previous terminus between 5 and 10 km downvalley. After subtracting the elevation of the land surface (determined from topographic maps) from the reconstructed glacier surface, and calculating former ice surface slope, ice thickness and basal shear stress distributions were determined. Sediment texture and the location of flutes on a morainal topographic high, downglacier from a proglacial lake basin, allowed high porewater pressures to develop as glaciers extended to terminus positions in the Saskatchewan Glacier Valley. Sediment strength was reduced sufficiently below values of reconstructed shear stress plots to allow deformation creating flutes. The absence of a similar topographic high and different sediment textural characteristics in the Kiwa Glacier Valley resulted in lower porewater pressures and consequently less reduction in sediment strength preventing the development of glacial flutes despite higher shear stress values here. Results indicate that the degree to which sediment characteristics and porewater pressure allow reduction of subglacial sediment strength relative to basal shear stress is important in determining conditions when flutes may develop. 相似文献
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Jansson and Glasser (Jansson, K.N., Glasser, N.F., 2008. Modification of peripheral mountain ranges by former ice sheets: the Brecon Beacons, southern UK. Geomorphology 97, 178–189.) have recently provided unconventional interpretations of selected glacial erosional and depositional landforms in the Brecon Beacons, UK, based on remotely sensed imagery. These new interpretations contradict well-established and reliable evidence for the origins and ages of certain glacial landforms of this upland area and elsewhere. They suggest that during a post-Last Glacial Maximum (LGM) ice-sheet event ice flowed up supposed, essentially “fluvial” valleys producing “glacial lineations” and depositing marginal moraines at the valley heads and on cirque floors. We argue that their interpretations of some key landforms are incorrect and that they have ignored much of the previous dating and field geomorphological evidence. Sedimentary and morphological evidence (e.g., lack of erratic content; convex planform with respect to the headwall; relatively large height range of moraines; and close association with headwall extent, height, and steepness) all indicate that higher level cirque-floor and valley-head moraines in the Brecon Beacons (> c. 400 m) were formed by cirque glaciers. Available dating evidence indicates a Younger Dryas age. We demonstrate that the supposed “fluvial” valleys, comprising trough heads with steep headwalls, have more nearly parabolic than V-shaped cross profiles indicating substantial glacial modification. Field evidence shows that proposed key exemplar post-LGM glacial lineations are in fact debris flow deposits. We conclude that whilst the adoption of a macroscale approach can shed new light on large-scale, ice-sheet movements, this approach should not be undertaken without consideration of the associated field evidence. 相似文献
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中国冰川区表碛厚度估算及其影响研究进展 总被引：5，自引：1，他引：4
表碛覆盖型冰川是中国西部分布较为广泛的冰川类型,其典型特征是冰川消融区部分或全部覆盖了一层厚度不一的表碛。与裸冰或雪相比,表碛覆盖层下冰的融化过程有独特性,表碛厚度空间分布对一条冰川的消融、物质平衡和径流过程的影响有别于无表碛覆盖型冰川。本文回顾了近年来表碛厚度分布及其影响的研究,通过对这些进展进行总结以进一步明晰表碛影响研究的方向;同时着重介绍了近期发展的基于遥感影像热红外波段和可见光近红外波段、大气—表碛层—冰川界面能量平衡过程的表碛厚度估算方法和表碛覆盖综合评估模型,结合地面观测,分析了以遥感反演的表碛层热阻系数表征表碛厚度的精度,介绍了这类模型在表碛覆盖型冰川物质平衡和径流研究中的应用效果,以及在综合评估流域/区域尺度表碛影响的应用情况,并分析了该模型存在的不足及进一步改进的研究方向,为实现中国西部区域表碛影响的系统评估奠定基础,从而提升对区域水资源和冰川灾害的模拟和预测能力。 相似文献
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Limestone and ophiolite rocks are common across the eastern Mediterranean and many of the highest mountains are formed in these rock types. In northwest Greece, Pleistocene glacial erosion was much more effective on limestone terrain where pronounced glacial incision and subglacial glacio-karst processes produced locally-complex topography. This enabled Pleistocene glaciers to form on a range of slope orientations in contrast to ophiolite terrains, where glaciers were strongly controlled by aspect. On limestone terrains, the largest ice masses formed on south-facing slopes, whereas in neighbouring higher mountains formed in ophiolite, glaciers were much more restricted and predominantly formed on north- and east-facing slopes. 相似文献
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气候和地貌对晚第四纪冰川发育差异性的影响 总被引：1，自引：1，他引：0
中国第四纪冰川作用极大地推动了高亚洲乃至全球冰川形成机制的探讨。青藏高原以及喜马拉雅山地冰川作用的时限和规模研究得到了广泛关注,为西风带与西南季风带对晚第四纪冰川作用差异性问题的解决提供了有利条件。然而,对于中亚西风环流与东亚季风环流影响下的冰川演化差异性关系不甚明确,两大气候系统控制下的山地第四纪冰川的冰进时序、冰期历史和冰川规模显示出不同特点,其差异性主要体现在:西部山地的冰期启动时间早,冰川规模随时间而逐渐缩小,冰川历史较为完整,绝对年代证据显示冰川作用的启动时间是450 ka 左右的中梁赣冰期(MIS12);东部山地的冰期历史较短,仅保留末次冰期(~75 ka)的冰川遗迹,冰川作用的阶段性明显;冰川演化时间与空间的差异性表明,影响冰川发育的因素不仅仅是区域气候,构造因素也起着相当重要的作用。 相似文献
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G. S. Bordonskii A. A. Gurulev V. A. Obyazov A. O. Orlov S. V. Tsyrenzhapov 《Geography and Natural Resources》2012,33(1):87-91
Considered are some results of radio sensing conducted for the Kheetei karst ice cave in Zabaikalskii region. The cave roof
was investigated by the active and passive radar techniques and infrared imaging. Revealed were sources of heat, air flows
and the dislocation of rocks along the fissure under the hoar-frost layer. This technique may be used in regular measurements
in order to study both changes in conditions of hollow subterranean formations and thermal processes in the environment. 相似文献
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Jessica L. Gary Steven M. Colman Nigel J. Wattrus C. F. M. Lewis 《Journal of Paleolimnology》2012,47(3):299-311
Glacial Lake Agassiz, the largest of the North American glacial lakes, discharged through several different outlets during
its history, although the timing and location of discharge remain controversial. However, one discharge event is well established
based on extensive onshore observations: drainage through the Nipigon Lake area into the Superior basin about 10,700 years
ago, following retreat of ice of the Marquette advance from the basin. High-resolution, single-channel seismic-reflection
data collected with a small airgun were acquired to test the hypothesis that the Post-Marquette drainage event left diagnostic
stratigraphic and geomorphic signatures beneath Lake Superior. The unique bathymetry of northwestern Lake Superior, where
water depth plunges off Nipigon and Black Bays, makes this location ideal for the characterization of the post-Marquette depositional
and erosional features. According to our hypothesis, the initial, sudden discharge of high-velocity water would have eroded
channels through the bays. The steep and sudden drop-off into the Superior basin would have caused the flow to slow and drop
much of the sediment it was carrying. Our results confirm the existence of both erosional features and depositional sediment
packages related to Lake Agassiz discharge at this time. The erosional features include deeply incised bedrock channels in
the bays. The depositional features comprise subaqueous fans that are thickest in the deep water areas adjacent to the outlets
and thin lakeward and laterally away from the channels. The seismic character of the basal units of the fans, proximal to
the channels, is chaotic and only very weakly stratified, suggesting that these deposits represent coarse sediment laid down
during the initial, high-energy stages of the flood. These sediments are overlain by a stratified package which is interpreted
as the fine grained sediment associated with the later, low-energy stages of the flood. The combination of channels and subaqueous
fans is inferred to be diagnostic of high-energy Lake Agassiz discharge into the Superior basin, and they serve as analogs
for hypothesized discharge at other times. 相似文献
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Pleistocene glacial erosion left a strong topographic imprint in the northwestern Sierra Nevada at many scales, yet the specific landforms and the processes that created them have not been previously documented in the region. In contrast, glaciation in the southern and central Sierra was extensively studied and by the end of the 19th century was among the best understood examples of alpine glaciation outside of the European Alps. This study describes glacially eroded features in the northwest Sierra and presents inferred linkages between erosional forms and Pleistocene glacial processes. Many relationships corroborate theoretical geomorphic principles. These include the occurrence of whalebacks in deep ice positions, roches moutonnées under thin ice, and occurrence of P-forms in low topographic positions where high subglacial meltwater pressures were likely. Some of the landforms described here have not previously been noted in the Sierra, including a large crag and tail eroded by shallow ice and erosional benches high on valley walls thought to be cut by ice-marginal channels. 相似文献
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Reconstruction and Regional Significance of the Coire Breac Palaeoglacier,Glen Esk,Eastern Grampian Highlands,Scotland 
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下载免费PDF全文 Martin P. Kirkbride Wishart A. Mitchell Mhari Barnes 《Geografiska Annaler: Series A, Physical Geography》2015,97(3):563-577
We present a glaciological and climatic reconstruction of a former glacier in Coire Breac, an isolated cirque within the Eastern Grampian plateau of Scotland, 5 km from the Highland edge. Published glacier reconstructions of presumed Younger Dryas‐age glaciers in this area show that equilibrium line altitudes decreased steeply towards the east coast, implying a arctic maritime glacial environment. Extrapolation of the ELA trend surface implies that glaciers should have existed in suitable locations on the plateau, a landscape little modified by glaciation. In Coire Breac, a 0.35 km2 cirque glacier existed with an equilibrium line altitude of 487 ± 15 m above present sea level. The equilibrium line altitude matches closely the extrapolated regional equilibrium line altitude trend surface for Younger Dryas Stadial glaciers. The mean glacier thickness of 24 m gives an ice volume of 7.8 × 106 m3, and a maximum basal shear stress of c. 100 kPa?1. Ablation gradient was c. –0.0055 m m?1, with a mean July temperature at the equilibrium line altitude of c. 5.1°C. The reconstruction implies an arctic maritime climate of low precipitation with local accumulation enhanced by blown snow, which may explain the absence of other contemporary glaciers nearby. Reconstructed ice flow lines show zones of flow concentration around the lower ice margin which help to explain the distribution of depositional facies associated with a former debris cover which may have delayed eventual glacier retreat. No moraines in the area have been dated, so palaeoclimatic interpretations remain provisional, and a pre‐Lateglacial Interstadial age cannot be ruled out. 相似文献