【作者】 黄雷； 张云翔； 弓虎军；

【Author】 HUANG Lei ZHANG Yunxiang GONG Hujun (Key Laboratory of Continental Dynamics of the Ministry of Education and Department of Geology,Northwest University,Xi’an 710069,Shaanxi)

【机构】 西北大学大陆动力学教育部重点实验室地质学系；

【摘要】 甘肃临夏盆地新近纪红黏土粒度研究表明,临夏盆地十里墩剖面55.80～5.00 m(何王家组)及层段158.75～58.95m(柳树组)中的大部分层位粒径以粉砂级(5～50 μm)含量为主,粒度分布曲线表现为单峰、偏正态分布,概率累积曲线呈简单的单段或两段式形态,判别值小于零,以上特点皆表现出它的风成成因:在柳树组中偶尔间层出现一些层段粗粒径(>63μm)含量相对较高,粉砂级含量相对较小,粒度分布曲线表现为双峰不对称特征,概率累积曲线呈复杂的多段式,判别值大于零,该类层段在剖面上表现为薄层疏松透镜状砂砾岩,说明该类层段具水成成因的特点。更多还原

【Abstract】 Linxia Basin is a Cenozoic fault basin situated at the boundary area between TibetanPlateau and the Loess Plateau.Because of its particular geographical position,Linxia Basincontains plenty of information about the uplift of Tibetan Plateau,the formation of theLoess Plateau and the evolution of the east Asian monsoon,and attracts attention ofgeologists worldwide who concern about global environmental change.Neogene red claywildly spreads in the basin,but its genesis still have different opinions.Based on thegranularity analyses,we discussed in this paper the genesis of the Red Clay from LinxiaBasin.Granularity analyses show that more than 55 percent grains in the Hewangjia groupand most layers of the Liushu Group are composed of silt size(change from 5μm to 50μmin width),the typical grain-size of blowing,while coarse grains(>63μm)in these strata areless than 4.5 percent.These samples display unimodal abnomal grain-size distributioncurves,single segment or two segments grain-size cumulative curves and the negativediscriminant values.All of these show the characteristics of eolian deposits.The content of coarse grains(>63μm)in some layers are relatively high,and in veryfew layers it is more than 78%,but silt grain is relatively low.These layers occur as thinlentoid sandy gravel in the Red Clay section,and show the dimodal asymmetric grain-sizedistribution curves,the complicated multistage grain-size cumulative curves and thepositive discriminant values.These permit us to think that these layers may be formed bythe fluvial deposits.更多还原