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1.
Norikazu Matsuoka 《Geomorphology》1995,12(4)
Field observations of weathering processes and the related landforms, combined with laboratory analyses of weathering products, permit a synthetic evaluation of Late Cenozoic weathering environments in the Sør Rondane Mountains, Antarctica, an arid upland characterized by low temperatures and strong winds. Rates and character of weathering depend mainly on moisture availability and the bedrock geology. Under the humid weathering regime that occurs only locally around the margin of the present sheet, frequent diurnal freeze-thaw cycles in summer cause relatively rapid rock fragmentation. Most of the mountains are situated in the arid weathering regime, under which rock breakdown is very slow unless the rock contains plenty of salts. Salt weathering becomes more intensive and extensive with exposure age, as a result of salt accumulation in rock, eventually producing soils as small as fine-silt size. Lack of clay mineralization even in weathered rocks having been exposed above the ice sheet prior to 4 Ma ago indicates that hydrolysis or carbonation of rock minerals has been insignificant during the past 4 Ma. The final products of weathering are due mainly to salt action and reflect the parent lithology. Resistant fine-grained granite forms strongly oxidized tors carved with tafoni, or fields of mushroom-like boulders overlying the fractured bedrock. Less resistant rocks, like biotite gneiss and amphibolite, produce stone pavements underlain by saline, silty soils up to 30–40 cm thick, the thickness of which corresponds to the maximum thaw depth. 相似文献
2.
Weathering processes in the Ellsworth Mountains of Antarctica are dominated by frost action. These processes were observed to be different on the same group of marbles under different slope conditions. North- and south-facing walls of the bedrock showed the same shattering rate in the summer of 1992–1993. Frost shattering of rocks is controlled by surface temperature, moisture, and the physical properties of the rock. The most important control on frost shattering in this area was moisture availability, given the same bedrock and freeze-thaw cycle. Snow particles are moved by katabatic winds, bringing moisture to the rock. Moisture is collected mainly in lower cliffs and cols. [Key words: weathering, marble, moisture conditions, Antarctica.] 相似文献
3.
GEORG SCHWAMBORN LUTZ SCHIRRMEISTER FRANZISKA FRÜTSCH BERNHARD DIEKMANN 《Geografiska Annaler: Series A, Physical Geography》2012,94(4):481-499
The object of this study is to test the assumption that cryogenic weathering (here understood as in‐situ disintegration of rock under cold‐climate conditions including ice as a weathering agent) preferentially breaks up quartz grains. We apply the results of laboratory tests to a Quaternary sediment record. The combination of silt production, relative quartz enrichment in the silt fraction, and quartz grain micromorphology is traced in a multi‐100‐kyr lake sediment archive as indicator data for cryogenic weathering. Constant cryogenic weathering conditions are inferred for at least the last 220 000 years from a lake sediment core of El'gygytgyn Crater, northeast Russia. This is the longest continuous terrestrial archive currently known for the continental Arctic. Quartz enrichment in the fines evolves from seasonal freeze–thaw weathering as demonstrated in laboratory testing where over 100 freeze and thaw cycles crack quartz grains preferentially over feldspar. Microscopic grain features demonstrate that freeze–thaw cycling probably disrupts quartz grains along mineral impurities such as bubble trails, gas–liquid inclusions, or mineralogical sub‐grain boundaries. Single‐grain micromorphology (e.g. angular outlines, sharp edges, microcracks, brittle surfaces) illustrates how quartz becomes fragmented due to cryogenic cracking of the grains. The single‐grain features stemming from the weathering dynamics are preserved even after a grain is transported off site (i.e. in mobile slope material, in seasonal river run‐off, into a lake basin) and may serve as first‐order proxy data for permafrost conditions in Quaternary records. 相似文献
4.
Influence of rock strength on the valley morphometry of Big Creek, central Idaho, USA 总被引：1，自引：0，他引：1
Zachery M. Lifton Glenn D. Thackray Robert Van Kirk Nancy F. Glenn 《Geomorphology》2009,111(3-4):173-181
Analysis of valley morphometry and bedrock strength along Big Creek, central Idaho, shows that valley floor width is strongly controlled by bedrock. We performed statistical analysis of Schmidt hammer rock strength as a function of lithology and aspect and of valley morphometry as a function of rock strength. Rock strength is significantly greater on the south side of the valley and in Eocene granodiorites. Rock strength is weakest in Eocene volcanic tuffs. Valley floor width depends negatively on weakest valley-side rock strength, and hillslope gradient on the north side of the valley depends positively on rock strength. Stream gradient does not depend on rock strength. Valley floor width appears to be controlled by bedrock strength on the weaker side of the valley, which was generally the north (south-facing) side. We speculate that a higher degree of weathering via freeze–thaw cycles contributes to lower strength on the north side. The positive dependence of hillslope gradient on rock strength on the north side provides evidence that differential weathering across lithologies determines the gradient that can be maintained as lateral migration of the stream erodes valley walls. These results suggest that in situ rock strength exerts strong influences on some measures of valley morphometry by modulating hillslope mass wasting processes and limiting lateral erosion. 相似文献
5.
Microweathering of ice-smoothed bedrock surfaces was investigated in the Røldal area of Hardanger Plateau (60°), southern Norway. Postglacial rates of weathering were determined from surface lowering using quartz veins as reference surfaces. Weathering processes are inferred from assessment of weathering rind formation, surface hardness, and the preservation of small-scale glacial erosional features.Surface lowering rates for a range of metamorphic rocks vary from 0.05 to 2.20 mm ka− 1 and are broadly comparable with those obtained from crystalline rocks in other periglacial environments. The mean rate of surface lowering at 0.55 mm ka− 1 is low and demonstrates the relatively small impact of microweathering on postglacial landscape evolution. Variations in bedrock microweathering can be explained by lithological variation. Amphibolite and mica-rich bedrock surfaces experience greater denudation and weakening, least weathering rind formation, and abundant preservation of glacial striae, despite greater surface lowering. Conversely, quartz-rich bedrock surfaces are most resistant to denudation and weakening, but have greater weathering rind formation and fewer preserved striae. Postglacial microweathering is achieved primarily through granular disintegration involving detachment and removal of mineral grains and weakening from increased porosity. Granular decomposition is manifest in the formation of weathering rinds. Analysis of interactions between weathering indices indicates that rind accumulation is limited by microerosion.A conceptual model is proposed that illustrates the temporal interrelationships between in situ and erosional facets of microweathering in two contrasting mineral assemblages. The model proposes that cyclic processes of in situ disintegration, decomposition, and erosion are at work. The relative balance between these processes varies with lithology so that in more resistant quartz-rich rocks the net effect is minimal surface lowering and accumulation of weathering rind. In weaker, amphibolitic and micaceous rocks, the net effect is greater surface lowering and minimal accumulation of weathering rind. The results of the research demonstrate the important influence of rock properties, notably mineral composition, in postglacial microweathering of crystalline bedrock in a periglacial environment. 相似文献
6.
STEFAN GRAB 《Geografiska Annaler: Series A, Physical Geography》2007,89(3):185-193
Rock temperature data are presented for a variety of topographic localities at a high Drakensberg site. The objective is to investigate the spatiotemporal variations of surface rock temperatures in high Drakensberg basalt. The temperature results are then used to discuss possible implications for thermal stress fatigue and frost‐induced weathering. Tinytalk? data loggers and probes were used for rock‐surface temperature recording. Long‐term measurements were recorded over 12 months from May 2002 to April 2003, at a 1‐hour logging interval and rock depth of 1 cm for a highaltitude (3300 m a.s.l.) interfluve and fracture site. Whilst the north‐facing rock surface experiences negligible hours below ?3°C, the south‐facing rock surface and interfluve sites are subjected to considerable periods below ?3°C, which falls within the ‘frost cracking window’. It is concluded that the substantial contrasts of recorded rock thermal parameters over small spatial scales between various topographic settings, highlight that site‐specific measurements across the broader scale are required for an adequate evaluation of regional weathering and its associated landform development. 相似文献
7.
The acquisition of a freezing remanent magnetization (FRM) has been studied in controlled magnetic and thermal environments by successive freezing and thawing (−18 to +20°C) of samples of natural sediments from a frost polygon near Ny Ålesund, Spitsbergen. Successive freeze-thaw cycles cause a significant decrease in the intensity of the initially induced shock remanent magnetization (SRM), associated with directional trends towards the ambient magnetic field direction during the freezing phase. A slow increase in intensity commences after seven to 10 freeze-thaw cycles. The acquisition of a FRM in samples carrying an isothermal remanent magnetization shows a significantly smaller reduction in intensity and only minor directional variations. This result indicates that only a fraction of the magnetic grains in a natural sediment contributes to the natural remanent magnetization. Insignificant changes in lengths and directions of the principal susceptibility ellipsoid axes also indicate that magnetic fabric and remanent magnetization are carried by partly different populations of magnetic grains.
The acquisition of a FRM in nature has yet to be explored. If such a process is confirmed, however, it has the potential for obtaining age estimates of ancient thaw depths and for providing insights into material transport processes in frost polygons. 相似文献
The acquisition of a FRM in nature has yet to be explored. If such a process is confirmed, however, it has the potential for obtaining age estimates of ancient thaw depths and for providing insights into material transport processes in frost polygons. 相似文献
8.
Norikazu Matsuoka Cline E. Thomachot Chiaki T. Oguchi Tamao Hatta Masahiro Abe Hiroyuki Matsuzaki 《Geomorphology》2006,81(3-4):408-420
Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma− 1. The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition. 相似文献
9.
《极地研究》1992,3(2):8-27
The chief aim of this study is to investigate the chemical weathering process of the weathering crust in Great Wall Station region of China (in Fildes Peninsula), Antarctica by the method of sedimentology. CW,SW,GW,TW,WE weathering crusts developed on volcanic clastic rock, gray aptitic basalt with tuff or basaltic bedrock. On change of minerals, geochemical behaviors of elements, migration and enrichment regularities of elements, Correlation between element geochemical behaviors, change of weathering potential of rocks in chemical weathering process are studied by us. We can see that the sequence fo weathering strengths of the abovementioned sections, from high to low, should reflected in TW, GW, CWand SWF and basical correspond with that calculated from the enrichment and differentiation indexes. 相似文献
10.
QUANTITATIVE FIELD OBSERVATION ON FROST PHYSICAL WEATHERING IN THE GREAT WALL STATION AREA 
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下载免费PDF全文 《极地研究》1992,3(2):32-37
Field observing sites were set fo measure frost weathering of bedrock in the Great Wall Station Area of Antarctica from 1988 to 1990. The results show that: (1), the weathering rate is higher in summer that in winter; (2), the weathering rate is greater at higher place than at lower place; (3), the weathering rate is higher in east and southeast slopes than in other slopes; (4), the weathering rate is greater in higher mean annual air temperature year than in lower year. 相似文献
11.
An investigation of periglacial slope stability in relation to soil properties based on physical modelling in the geotechnical centrifuge 总被引：3，自引：0，他引：3
Results are presented from eight scaled centrifuge modelling experiments designed to investigate mass movement processes on thawing ice-rich slopes. Four pairs of simple planar slope models were constructed, one in each pair being of sufficient gradient to promote slope failure during soil thaw and the second having a gradient below the threshold for instability. Four frost susceptible soils were used, three were normally consolidated and had different clay contents (2%, 12% and 20%) and the fourth comprised the 20% clay soil, but was over consolidated prior to model testing. Modelling protocols included freezing from the surface downwards under an open hydraulic system, and thawing from the surface downwards under an enhanced gravitational field within the geotechnical centrifuge, thereby utilising scaling laws to simulate correct prototype self weight stresses during thaw. Slopes below the stability threshold gradient were subjected to between 2 and 4 cycles of freezing and thawing, simulating annual cycles. Those above the stability threshold were subjected to only one cycle, since they failed during the first thaw phase. Thermal conditions, pore water pressures, surface movements, and profiles of displacement are reported. Measured pore pressures are used in slope stability analyses based on a simple planar infinite slope model. Profiles of solifluction shear strain and mechanisms of slope failure are both shown to be sensitive to small changes in soil properties, particularly clay content and stress history. In all cases, pore pressures rose rapidly immediately following thaw, remained below the threshold for failure in low gradient models, but exceeding the threshold to trigger landslides on steeper slopes. Upward seepage of melt water away from the thaw front contributed to loss of shear strength. Mechanisms of slope failure differed between test soils, ranging from mudflow in non-cohesive silt to active layer detachment sliding in over consolidated silt–clay. During solifluction, shear strain was greatest at the surface in non-cohesive silt and decreased rapidly with depth, but in test soils containing clay, the zone of maximum shear strain was located lower in the displacement profiles. 相似文献
12.
D.N. Mottershead 《Applied geography (Sevenoaks, England)》1981,1(4):297-304
Spots of oil thrown up on to a coastal rock platform just above high water mark protect the rock beneath from weathering. Differential weathering subsequently leads to the emergence of oil-capped pedestals. Measurement of the rate of bedrock lowering of the surrounding surface by micro-erosion meter (MEM) provides a method of estimating the age of the pedestals and consequently the duration of oil persistence on the shore. The maximum duration of oil is estimated at 17–18 years. 相似文献
13.
Biancane badlands consisting of small domes dissected by rills and micropipes, with rough disordered microrehef, can be found along the Apennines in Italy. The dominant processes forming biancane differ from those of badlands formed on smectite-rich mudrocks, as micropipes associated with pseudokarstic enlargement of pores and cracks predominate and form the main routes for evacuation of eroded material.Biancana evolution is controlled by water infiltration into intact bedrock, producing an erodible weathering ‘rind’ which is more porous than intact rock. This rind is easily removed by rill or micropipe flow, and erosion is therefore ‘weathering-controlled’, depending on rind production by infiltrating water. Infiltration is initially slow and stepped, due to slow water movement through very small capillary pores in intact rock alternating with rapid filling of macropores and cracks. This occurs due to rapid matrix pore enlargement by dispersion and/or dissolution. The infiltration pattern is accurately reproduced by a model built on progressive development of weathering layers by moisture penetration. Model results are consistent with weathering rind depths and erosion observed in the field, and show that a pipe network can be generated on newly exposed rock by the rainfall of one year.Propagation of the pipe network diverts a progressively larger proportion of runoff into micropipes, expanding weathering rind production within the biancana as well as on the surface. Internal weathering and flow progressively dominate with few unweathered corestones, and the biancana gradually collapses into a penultimate “soufflé-like” form. 相似文献
14.
Kazakhstan regions is seasonal climatic with transient freezing of soil groundduring the winter. Roadbed integrity is important to resist the sustained load transmitted by traffic on the road surface. Freezing of soil ground could significantlyinfluence roadbed integrity in the seasonal freezing climate of Kazakhstan. The proper determination magnitude of frost heave and heaving pressure by the influence of freezing temperatures during the winter season are necessary for design and construction of highways. Thus, experimental tests were conducted on specimens obtained from Astana (Kazakhstan) to determine the freezing pressure and magnitude of frost heaving. 相似文献
15.
CHRISTINE ELLIOTT 《New Zealand geographer》2003,59(1):50-60
A review of some recent studies on rock weathering in Antarctica has revealed that Antarctic weathering research has a significant contribution to make to the ongoing debate about rock weathering in cold climates. Largely conducted in the field rather than the laboratory as in the Northern Hemisphere, it demonstrates that whilst all weathering processes can occur in Antarctica this is highly localised and dependent on the particular micro‐environment. Freeze‐thaw, for example, is not the most dominant process in many parts of Antarctica. The right combination of rock temperature and moisture can mean that salt, insolation, hydration or even chemical weathering can predominate. 相似文献
16.
Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, bridge stiffness is also
measurably higher in winter months. Significant changes due to seasonal freezing in bridge pier boundary conditions require additional
detailing in order to ensure a ductile performance of the bridge during a design earthquake event. This paper reports the latest
results obtained from a project that systematically investigated the effects of seasonally frozen soil on the seismic behavior of
highway bridges in cold regions. A bridge was chosen and was monitored to study its seismic performance and assess the impact
of seasonally frozen soil on its dynamic properties. A Finite Element (FE) model was created for this bridge to analyze the impact
of seasonal frost. It was found that when frost depth reaches 1.2 m, the first transverse modal frequency increases about 200%
when compared with the no-frost case. The results show that seasonal frost has a significant impact on the overall dynamic behavior
of bridges supported by pile foundations in cold regions, and that these effects should be accounted for in seismic design. 相似文献
17.
浙江缙云县大洋山石鼓尖花岗岩坑穴成因 总被引：3，自引：0，他引：3
浙江缙云县大洋山石鼓尖海拔1477m,在其山顶花岗岩表面发现大量直径几十厘米至1m左右、深度10cm至45cm的坑穴。经对60处坑穴的形态量测发现,坑穴主要发育在山坡的NE和SE一侧;坑穴积水后出水口流向亦主要朝向NE和SE。对岩石标本的偏光显微镜和X荧光光谱鉴定分析发现,该处基岩为易风化、泥化明显的中细粒钾长花岗岩。该处年平均气温9.2oC,年降水量在1700mm以上,每年12月至翌年3月会经历4个月日气温在0oC上下波动的冰缘作用期,雨雪水冻融交替对基岩的崩解作用明显。该处位于夏季台风雨迎风坡（NE和SE坡）一侧,暴雨常伴随有10级以上大风。现场常可见风力吹蚀带动坑穴中细岩屑对坑穴内壁产生加速旋转磨蚀作用。上述研究表明,该处花岗岩坑穴形成的主要动力成因首先是冰缘寒冻风化作用,暴雨和山顶大风的风力吹蚀加速了坑穴的形成。观察表明,此种作用目前仍在进行之中,风向的转变是造成坑穴出现多种形态的主要原因。由于此处海拔距雪线尚有1500m高差,即使在第四纪盛冰期也仅是接近雪线高度,且因山顶无积雪屯冰的低洼地形,因此,第四纪“冰臼”成因说难以成立。 相似文献
18.
A granitic rock avalanche, one of the largest Quaternary landslides in Arizona outside the Grand Canyon with a volume of approximately 5.25 M m3 and a width a little under 0.5 km, ran 1 km from the eastern McDowell Mountains. With lateral levees and pressure ridges, the rock avalanche deposit displays many features found on classic sturzstroms. Failure occurred along a major joint plane paralleling the slope with a dip of 44°, when a major base level lowering event in the Salt River system would have undermined the base of the failed slope, and probably during a period of more moisture than normally available in the present-day arid climate. Failure at the subsurface weathering front highlights the importance of the dramatic permeability change between grussified regolith and relatively fresh bedrock. Rock varnish microlaminations (VMLs) dating, in concert with other geomorphic evidence, suggests that the rock avalanche deposit is slightly older than 500 ka. The rock vanish results also have important implications for sampling strategies designed to use cosmogenic nuclide to date Quaternary landslide deposits. Discovery of a large landslide in close proximity to the extending urban fringe of metropolitan Phoenix argues for a more careful analysis of landslide hazards in the region, especially where rapid development excavates bedrock at the base of steep mountain slopes and where the subsurface weathering front is near the surface. 相似文献
19.
丹霞山顺层洞穴风化特征的试验研究 总被引：1，自引：1，他引：0
以丹霞盆地丹霞组2段顺层洞穴为研究对象,探讨不同岩性红层抗风化能力的差异,重点关注软岩夹层的风化特征及其对顺层洞穴发育的影响。在野外考察的基础上,选择3个典型顺层洞穴为案例,采集了洞穴剖面不同岩性红层的岩样及夹层水样品,进行一系列的岩矿理化测试和水样分析实验。结果表明：洞穴剖面岩性的不均一性及软岩夹层的风化凹进是形成丹霞山顺层洞穴的主要原因。顺层洞穴发育的软岩夹层一般是粉砂质泥岩,粘土矿物含量高,以泥质胶结为主,吸水性较强,开型空隙率较大,抗压强度小,易于风化破碎;上下岩层主要是砂岩和砂砾岩,以钙质和铁质胶结为主,吸水性较弱,开型孔隙率较小,抗压强度较大,风化速度较慢。在洞穴岩层风化过程中,粘土矿物的胀缩、钙质胶结物的溶解, 及铁质胶结物的水化作用等是导致岩体结构破坏的重要因素,但促使不同岩性红层风化的主导因素有所差别。粉砂质泥岩的风化以粘土矿物的胀缩作用为主,砂岩和砂砾岩的风化则以钙质胶结物的溶解作用为主。此外,酸性雨水渗入岩体后与各种矿物进行的一系列离子交换作用也促进了顺层洞穴岩层的风化。 相似文献
20.
区域地下水溶解性碳的时空变化特征研究对于认识区域物质循环和能量传递及推动区域生态可持续发展具有重要意义。本研究在青海湖流域冻结期和融化期分别收集了地下水、河水和湖水样品,研究了环青海湖地下水在冻结期和融化期的溶解性碳特征,并探究了不同类型地下水的溶解性碳特征及其对不同冻融时期的响应,最后揭示了环湖区域不同水体的溶解性碳的差异特征及影响因素。结果表明：冻结期地下水、河水和湖水的溶解性无机碳（DIC）均相对高于融化期,溶解性有机碳（DOC）均相对低于融化期。地下水、河水和湖水的溶解性碳均主要以DIC为主,DIC在溶解性碳的占比高达92%。地下水的DIC平均含量在基岩裂隙水、水量中等和浅埋藏的水文地质条件下相对较高,DOC平均含量在基岩裂隙水、水量丰富和浅埋藏的水文地质条件下相对较高。地下水的DIC在湖滨平原砂砾石层、淤泥质砂层潜水和水量中等的水文地质条件下受冻融期影响较大,DOC在基岩裂隙水和水量贫乏的水文地质条件下受冻融期影响较大。湖水的DIC和DOC均远高于河水和地下水。河水的DIC在融化期和冻结期均低于地下水,DOC在融化期高于地下水,在冻结期低于地下水。 相似文献