【摘要】 本文通过对甘孜满地黄土的粒度组分、石英砂的表面结构以及其它地质现象的综合研究,对甘孜黄土的成因进行了探讨。在黄土的概率累计曲线上,跃进组分和悬移组分反映明显,并以悬移组分为主。悬移组分粒径小于2～3,并以粉砂(4～8)为主,占悬移总体的94%～99%;对甘孜黄土进行扫描电镜观察表明,石英砂大部分为块状颗粒,少量(10%)呈纺锤形。采用矩阵法计算甘孜黄土的粒度参数:黄土的平均粒径(d50)为5 057～5 883,明显大于古土壤(6 120～6 549)。古土壤的标准偏差(σ)为1 513～1 973,大于黄土(1 205～1 778);黄土和古土壤的偏度系数(SK)为-0 088～0 248,显示为正偏或近于对称。黄土和古土壤的尖度系数(K)分别为0 123～1 702、0 023～0 059,前者峰形窄,后者峰形较宽。对甘孜黄土扫描电镜观察表明,石英砂大部分为方形或长方形颗粒,少量(10%)呈纺锤形。石英砂有密集的翻卷片、蛇曲脊、圆麻坑,这些结构反映了风成特征。另方面,少量石英砂显示冰川作用结构,例如大大小小的贝壳状断口、平行擦痕等。在甘孜西面、德格以南的金沙江东岸川藏公路980km路碑处,三阶地上部的黄土层中,发现3条冰楔。此外,甘孜黄土中孢粉稀少。根据上述特征推断,甘孜黄土应为冰缘风成黄土。更多还原

【Abstract】 The Ganzi Loess origin in the West Sichuan Plateau has been discussed based on synthetic study in grain composition of the loess,surface texture of quartz sand,as well as other geological phenomena.On the cumulative curve of grain size distribution in Ganzi Loess of logarithmically probability graph paper,saltation mass and suspension are obvious,and the later is principal.In the suspension,the grain size is not more than 2～3 in diameter,and the silt grains (4～8)are principal.The grain size parameters of Ganzi Loess were counted by the matrix method.Its mean grain size is 5057～5883, and bigger than one of fossil soil in the loess.The 1513～1973 of standard deviation (σ)of fossil soil is bigger than the loess (1205～1778). The skewnesses (Sk)of the loess and fossil soil are -0088～0248.The kurtosis (K)of the loess is 1242～1702,and the one of the fossil soil is 0023～0059.The quartz sand surface textures of Ganzi Loess have been observed with Scanning Electron Microscope.Most of quartz sands are blocky,and a few of grains are fusiform.On the surfaces of the quartz sands,there are a number of aeolian features,such as concentrated upturned plates meandering ridges,pocks,and others.These ones are characteristics of aeolian origin.On the other hand,a few of the quartz sands are characterized by glacial surface textures,such as all sizes conchoidal fractures,and parallel striations.In the West Ganzi,and the South Dege,by the East bank of Jinsha River,three icewedges are discovered in the loess strata on the top of third order terrace.Furthermore,the sporopollens are scarce in the loess strata.As above,it appears that Ganzi Loess is aeolian sediment in the periglacial environment.更多还原