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Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens
on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of
epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns,
mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore,
it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic
weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out
in Antarctica. 相似文献
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Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns, mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore, it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out in Antarctica. 相似文献
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《极地研究》1992,3(2):1-7
Some weathering observation sites were set up at different height and face in Great Wall Station area of King Geroge Island, Antarctica, since 1989. Baced on the data series obtained from 1987-1991, the relationship between physical weathering of rock and season, height, face are discussed in this paper. We also compare the results to that of other periglacial area in the world in order to know the special features of King George Island in physical weathering of rock. The rock weathering in south-east face of sea stack is higher than that of north-west face in same environment. Get rid of influence of elevation, rock type, weathering time and organisms, the main reason which caused physical weathering of this area is climate and orientation of rock. The King George Island of Antarctica belong to high latitude area. The temperature time of below zero is 6-8 months in a year, so the process of freeze-thow is restricted. Compared with other periglacial area in the world, the weathering rate of rock is midd 相似文献
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１ＩｎｔｒｏｄｕｃｔｉｏｎＡｓｔｈｅｅａｒｌｉｅｓｔｃｏｌｏｎｉｚｅｒｓｏｆｔｅｒｅｓｔｒｉａｌｈａｂｉｔａｔｓｏｎｔｈｅｅａｒｔｈ,ｔｈｅｏｃｕｒｅｎｃｅｏｆｌｉｃｈｅｎｓｍａｙｂｅｄａｔｅｄｆｒｏｍｔｈｅＥａｒｌｙＤｅｖｏｎｉａｎ（Ｔａｙｌｏｒｅ... 相似文献
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Christine Elliott 《New Zealand geographer》2004,60(1):44-51
The importance of moisture in determining which rock weathering processes may operate, as well as the rate at which rock weathering occurs, has long been recognised. However, little is known about how often or when moisture is available to the rock surface, or for how long the surface may be wetted. This paper gives some initial results from current research on granite rocks in Antarctica. Recordings of surface moisture, for two aspects and three locations in Victoria Land, show that moisture reaches the rock surface more frequently than might initially have been expected in this dry climate. The number of occasions the surface is wetted, and the quantity of moisture the surface received, varied with aspect and time of year. Rock surfaces could be wet for up to 40% of the time during the summer months. This has important implications for rock weathering where some processes are deemed not to operate, or to operate in very restricted locations, due to the apparent absence of moisture. 相似文献
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《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
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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
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西南极南设得兰群岛乔治王岛菲尔德斯半岛土壤化学分析表明土壤中存在着一定的化学风化作用。相对于母质,土壤中的SiO_2、Al_2O_3、Fe_2O_3、FeO、MgO,GaO和Na_2O淋失,K_2O、H_2O~+、H_2O~-、TiO_2和P_2O_5富集。土壤中SiO_2/Al_2O_3的平均值为4.71,属弱风化壳类型。硅铝比反映出成土作用时间越长,土壤的风化程度越高,化学风化作用大于南极大陆边缘和内部。Al_2O_3在南极的淋失率大于SiO_2,使较老土壤剖面由下向上硅铝比增大。土壤的化学性质很大程度上取决于母质。南极强烈的冻融扰动作用破坏了土壤分层。土壤中存在着较强的水合作用。 相似文献
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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
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In situ quantification of localized weathering processes on basalt flows in New Mexico and Hawaii demonstrates that small‐area factors can be more important than other more readily observable factors. Further, it demonstrates that the factorial concept of the Pope Boundary‐Layer weathering model is partially solvable, that organic weathering can accentuate glass weathering (with implications for climate models and storage of nuclear waste), and that silica coatings are not a simple solution for the preservation of stone monuments. Enhancement of glass weathering by lichens on the McCartys flow, El Malpais National Monument, New Mexico, remains restricted to a half‐millimeter directly underneath the lichen‐covered surface. In contrast, although the inorganic rock coating of silica glaze reduces weathering directly underneath the coating by up to nine times rates found in uncoated locales, silica glaze can almost double variability in weathering along its margins. 相似文献
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Satoshi Ishimaru & Kenji Yoshikawa 《Geografiska Annaler: Series A, Physical Geography》2000,82(1):45-57
The weathering of granodiorite porphyry is examined in the extremely cold and dry environment of the inland part of Antarctica. Weathering features include granular disintegration, rock varnish, and sheeting. Sheeting has gradually proceeded since the exposing of the nunatak, but the other types of weathering have not actively advanced in recent times.
Granular disintegration primarily comprises the release of individual crystals. The mechanism of this release is that cracks are created along crystal boundaries and cleavages in phenocrysts mainly due to differential thermal expansion. Plagioclase and hypersthene are released more readily than quartz. Disintegration of plagioclase has produced many prism-shaped holes, 0.5 to 2.0 mm in length, while fine-grained quartz crystals, 0.05 to 0.1 mm in diameter, are incidentally released without cracking.
The reddish brown (10R4/4) rock varnishes result from oxidation and consist of limonite, which fills cracks and penetrates into crystals. Ferrous iron in hypersthene, biotite, ilmenite and magnetite is transformed into limonite by oxidation. Manganese is not found in the varnishes. Sulfur, which is important for oxidation and which may have originated from adhered snow, is concentrated on the surface of the rock.
Sheeting has precipitated rock falls, and has gradually formed a gray mosaic on the varnished wall. The sheeting was caused by gravitational body force, which is internal stress of the rock body due to the mass of the overburden. 相似文献
Granular disintegration primarily comprises the release of individual crystals. The mechanism of this release is that cracks are created along crystal boundaries and cleavages in phenocrysts mainly due to differential thermal expansion. Plagioclase and hypersthene are released more readily than quartz. Disintegration of plagioclase has produced many prism-shaped holes, 0.5 to 2.0 mm in length, while fine-grained quartz crystals, 0.05 to 0.1 mm in diameter, are incidentally released without cracking.
The reddish brown (10R4/4) rock varnishes result from oxidation and consist of limonite, which fills cracks and penetrates into crystals. Ferrous iron in hypersthene, biotite, ilmenite and magnetite is transformed into limonite by oxidation. Manganese is not found in the varnishes. Sulfur, which is important for oxidation and which may have originated from adhered snow, is concentrated on the surface of the rock.
Sheeting has precipitated rock falls, and has gradually formed a gray mosaic on the varnished wall. The sheeting was caused by gravitational body force, which is internal stress of the rock body due to the mass of the overburden. 相似文献
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本文通过对长城湾表层沉积物中稀土元素的地球化学研究,认为其总量丰度、配分模式、特征参数等,均与菲尔德斯半岛的火山岩相似,因而长城湾沉积物的主要来源似为菲尔德斯半岛基岩的风化产物。 相似文献
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The endolithic lichen Lecidea auriculata is known to enhance rock surface weathering on the Little Ice Age moraines of the glacier Storbreen in Jotunheimen, central southern Norway. This study demonstrates the reduction in Schmidt hammer Rvalues that followed the rapid colonization by this lichen of pyroxene‐granulite boulders on terrain deglaciated over the last 88 years. In the absence of this lichen, the characteristic mean R‐value of boulder surfaces is 61.0 ± 0.3; where this lichen is present, R‐values are lower by at least 20 units on surfaces exposed for 30–40 years. A similar reduction in rock hardness on rock surfaces without a lichen cover requires about 10 ka. The rapid initial weakening of the rock surfaces is indicative of rates of biological weathering by endolithic lichens that may be two orders of magnitude (200–300 times) faster than rates of physico‐chemical weathering alone. If not avoided, the effects of this type of lichen are likely to negate the effectiveness of the Schmidt hammer and other methods for exposure‐age dating, including cosmogenic‐nuclide dating, in severe alpine and polar periglacial environments. The results also suggest a new method for dating rock surfaces exposed for <50 years. 相似文献
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通过研究寒冻化学风化作用下的元素地球化学性状,包括化学元素的相关性分析,元素的集散特征,稀土元素的分布模式以及粒级对元素迁移的影响,粘土矿物对痕量元素的吸附作用等,得出不同地区风化壳的类型:长城站地区(西南极亚南极地区)形成碳酸盐层状风化壳;戴维斯站所在的维斯特福尔德丘陵区基岩上发育了弱风化碎屑的碳酸盐裂隙型风化壳;在凯西站地区,基岩的寒冻风化过程尚未进入最低风化度形成的碳酸钙壳阶段,而是完全处于风化最初始的碎屑型阶段. 相似文献
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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
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