25 February 1985, Volume 6 Issue 1

    

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  Studies of Ice Formation and Ice Fabric on the Law Dome, Antarctica

  Xie Zichu

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 1-23. https://doi.org/10.7522/j.issn.1000-0240.1984.0001

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  Snow Stratigraphical studies,together with crystallographic and oxygen isotope analyses, have affirmed the existence of a complete range of ice formation zones on the Law Dome, Antarctica. Between the coast and the Summit of the Dome the following 6 zones of progression are observed:abla-tion, infiltration-congelation(superimposed ice), infiltration, cold infiltra-tion-recrystallization,regelation and recrystallization. A warm infiltration-recrystallization zone is possibly found on the north east coast and is probably a result of the high accumulation in that area.The distribution of these zones on the Law Dome is asymmetric; the zone boundaries occur at a higher elevation on the west side than on the east side, reflecting the asymmetry in accumulation and thermal conditions.Snow pits dug near the boundaries of the zones show a change of the type of ice formation with depth, an evidence of climatic change in recent years. Near Cape Folger (northwest coast) replacement of infiltration zone ice by infiltration-congelation zone ice indicates an increase of summer temperatures over the last ten years.Crystallographic studies of ice from two boreholes near Cape Folger (BHCl and BHC2) show a change of microtexture and fabric of the ice crystals with depth. Six different layers can be identified: 1) A deposition layer, with polygonally shaped crystals increasingin size with depth. The c-axis orientation in this layer is dependent on the formation process of the ice.2) A transition layer with porphyrblastic crystals. The ice fabricpattern is a girdle, developing into a two pole fabric.3) A fine grained layer with cataclastic crystals and strong, nearlyvertical single-pole c-axis fabric. Air bubbles in the ice are elongated in the direction of ice flow.4) A coarse grained layer with large, interlocking, branched crystalsand a multi-maxima (diamond pattern) c-axis fabric.5) A second fine grained layer with cataclastic and interlockingcrystals, elongated air bubbles and a strong, single maximum fabric which is elongated in the direction of ice flow.6) A second coarse grained layer with large interlocking branchedcrystals and a multi-maxima fabric, the centre of symmetry of which is inclined away from the vertical.At the very bottom of the hole the ice contains dirt and moraine particles, and the microtexture shows that in each large crystal, the air bubbles have a preferred orientation in the basal plane. This indicates regelation-recrystallization, as the ice is at pressure melting and basal sliding occurs.Comparisons with borehole inclination and oxygen isotope data show that the two layers of single maximum fabric correspond to two layers of high ice shear and the second layer contains ice dating back to the period of the last glaciation.Two layers with a single maximum c-axis fabric were also found in the SGA borehole about 450 m upstream of BHC 1, and in the SGF borehole further 4 km upstream. The possible origin of second layer with a single maximum fabric is discussed. The author suggests that this ice results from conditions during the last glaciation.
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  Analysis of Microparticles in Ice Cores: An Indicator of Past Environments

  Lonnie G. Thompson

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 25-32. https://doi.org/10.7522/j.issn.1000-0240.1984.0003

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  The dry snow facies of continental ice sheets and ice caps contain par-ticulate material and isotopis species which provide information about the physical properties of the atmosphere at the time of precipitation formation and deposition. Major conclusions from the study of microparticles in four deep ice cores ares (1) Average particle concentration increased 300-1200% near the end of the Late Wisconsin over average Holocene values.(2) Particle concentrations during the last glacial stage exhibited large variations in amplitudes suggesting either rapid change in atmospheric conditions and/or particulate content of the atmosphere.(3) The transition Holocene/ Late Wisconsin is very abrupt taking place in less than 100 years.(4) Annual particle variations may be used to estimate time scales for ice cores and (5) Elemental compositions of paticles analyzed from deep ice cores indicate multiple sources.lt is suggested because of the great time involved in doing a complete analysis of a deep core and because of a lack of other detailed climate records over the last 50000 years that effort should be placed on establishing a detailed climate record for the last 1000 years from different latitudes. The detailed study of climatic ice core records over the past 1000 years will be more scientifically rewarding because larger quantities of other climate information exist to aid in the understanding of the ice core records. The detailed understanding of global climatic variations over the last 1000 years which will be most important in predicting future climate variations over the next 100 years.
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  Creep Behavior of Frozen Silt under Constant Unlaxial Stress

  Zhu Yuanlin, D. L. Carbee

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 33-48. https://doi.org/10.7522/j.issn.1000-0240.1984.0004

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  A series of tin confined compression creep tests was conducted on remol-ed,saturated frozen Fairbanks silt at constant-stress(σ) and constant-temperature conditions. It was found that a sudden change occurred in the slope of loge vs.1/σ curves at almost the same minimum strain rate(about 10^-6s^-1) for various test temperature. Therefore, the authors suggest that the creep of frozen soil be classified into two types- short-term creep and long-term creep. Different constitutive and strength-loss equations are presented for each type of creep. The criterion of creep failure of frozen soil is considered to have the general form of ε_m×t_mⁿ where n is a material constant dependent only upon water content, εf is the failure strain, and t_m is the time to failure in minutes. On the basis of Assur’s creep model (1980) and this criterion, a creep equation was derived that can describe the entire process of creep of frozen soil.
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  Preliminary Study on Quaternary Climate in China

  Guo Xudong

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 49-60. https://doi.org/10.7522/j.issn.1000-0240.1984.0005

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  On the basis of geological observations and laboratory analysis on the paleoclimatic indicators, including botanical pollen, paleosol, snowline, timberline, etc., the author of this paper has come to reconstruct the Quaternary climate of China as follows:(1) Under the influence of a world-wide Quaternary climatic change, the climatic environmental region in China can be divided into two distinct large areas; the glacial West part and non-glacial East part. In glacial area, the change of climate is from ice age to interglacial period, while in non-glacial area the change of climate is from cold to warm, which is quite different from that in glacial region.(2) During Pleistocene glaciations,a temperature depression of 10-131℃ lower than today in central Himalaya range has been deduced on the basis of the snowline depression. In the Qomolangma glaciation, a temperature depression of 3-4 ℃ occurred in central Himalaya and 4-8℃ occured in other alpine mountain regions.(3) During Pleistocene warm period, temperature was about 8-12℃ higher than today. In the postglacial interval of maximum warmth (optimum period) the average annual temperature was about 3-4 ℃ higher than today.(4) Judging from the change of botany, snowline, timberline and periglacial climate on the basis of the permafrost,it shows that no glacia- tion ever existed in the middle-lower ranges or hill and plain in the East of China. Therefore, Periglacial and interperiglacial existed there rather than glaciers.
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  A Preliminary Discussion on Influence of Tarim Basin upon the Glacier Development in Southern Tian Shan Mountains

  Wang Zongtai, Han Yuanjie

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 61-70. https://doi.org/10.7522/j.issn.1000-0240.1984.0008

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  The southern part of Tian Shan Mountains is located on the northern border of the great,dry and sultry Tarim Basin and situated on the northern edge of the Qinghai-Xizang Plateau where the high pressure takes a downward depression. Those two factors seem to be unfavorable for glacier development. But however, the glaciers here have a size greater than all the others in the central part of Tian Shan Mountains. The author of this paper discussed and suggested that a special local circular current between the southern Tian Shan and the Tarim Basin has made the change. During the summer period (May to September) there exists SW current flowing toward the southern slope of the southern Tian Shan Mountains at the 800mb-700mb layer. Meantime there is a thick wet layer over the Basin due to the convergence effect of the warm pressure, and a closing humid center above the western part of the Basin forms. Consequently, the local SW current brings up the warm vapour to alpine region of the mountains, and creates local rainfall, which joins with the west wind trough and the cold air mass from the north and forms the material basis for the large scale development of glaciers in this region.This local SW current is the joint product of the specific landform of the Basin and the thermal and dynamical effects of the desert ground surface. The convergence of the warm low pressure at the bottom and the down depression divergence of the warm high pressure over the top (tilt to the NE) are important to the development of glaciers. This problem is worth for further study.
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  Basic Characteristics of Periglacial Landforms on Wutai Mountain

  Zhu Jinghu, Cui Zhijiu

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 71-77. https://doi.org/10.7522/j.issn.1000-0240.1984.0009

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  Wutai mountain located near Wutai county in Shanxi Province is the highest peak (3058) in the North China. Both ancient periglacial phenomena and present periglacial phenomena have been developed. Periglacial landforms are as follows: cryoplanation surface, tors, blockfield, block slopes, stone stripes, stone circles, stone nets, polygons, frost block, turfs, solifluction lobes, blockstreams, thaw hollow, dells, stone-banked terraces, stone banks, periglacial loess, etc.Both ancient periglacial phenomena and present periglacial phenomena have relation originally on Mt. Wutai. In the late Pleistocene, the mean annual temperature was about 3-4℃ lower than that at present on the top of Mt.Wutai, but it is about 10-11℃ lower than that at present on the surface of Shanxi Plateau.There was a periglacial age in the late glacial age of the Quaternary in the Wutai Shan area and it was called the Wutai Periglacial age, but now it goes into a sub-Periglacial age.
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  On the Classification of Ground Water in the Permafrost Area in Qilian Shan

  Guo Pengfei

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1984, 6(1): 79-84. https://doi.org/10.7522/j.issn.1000-0240.1984.0012

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  In this paper, the ground water in permafrost area in Qilian Shan is studied and divided into three types according to its buried condition and spatial distribution; superpermafrost water, subpermafrost water and ground water of melting area. No interpermafrost water could be found. If the storage conditions and hydrodynamic properties of the ground water are comprehensively considered, 13 subdivisions could be obtained.