摘要
根据具有代表性的镇江大港剖面的粒度分析结果探讨了下蜀黄土的成因。结果表明 :镇江下蜀黄土主要由 <5 0μm细颗粒物质组成 ,>5 0μm的砂粒贫乏 ,平均含量仅占 4.18% ;5 0～ 10μm的粗粉砂含量为 49.36 % ,为众数粒组 ;10～ 5μm的细粉砂平均含量为 18.0 2 % ;<5μm的粘粒含量为 2 8.44 %。粒度概率累积曲线呈标准的二段式 ,频率分布曲线为单峰 ,粒度参数具有高度的一致性特征。粒度分析证实 ,镇江下蜀黄土与北方黄土一样同是大气粉尘堆积物。我国自西北向东南沿主风方向呈带状排列的砂黄土带 (柴达木黄土 )、典型黄土带 (黄土高原黄土 )、粘黄土带 (山东黄土 )、细粘黄土带 (宁镇下蜀黄土 )共同构成了我国独特的第四纪风尘堆积空间分布延伸序列 ,它们是在第四纪冰期干冷气候条件下气
There are different opinions on origin problem of the Xiashu Loess along the mid lower reaches of the Yangtze River.Based on the grain size analyses of representative section of the Xiashu Loess-Dagang section in Zhenjiang,the origin of the Xiashu Loess is discussed in this paper.The results show that:(1)the Xiahsu Loess in Zhenjiang mainly consists of fine particles that are less than 50 μm and no particles over 250 μm can be found,(2)the content of >50 μm particles ranges from 0% to 6 82% with the average content of 4 18%,(3)the 50～10 μm particle group ranges from 40 04% to 58 4% with the average content of 49 36% and is the “dominant group”of the Xiashu Loess,and (4) the average content of 10～5 μm group is 18 02% and <5 μm group occupies 28 44%.The grain size probability cumulative curves of Dagang section are characterized by the mode of double segment and the grain size frequency distribution presents single peak mode.The grain size analyses confirm that the Xiashu Loess in Zhenjiang is also the atmospheric dust sediment and it is of eolian origin just like the northern loess in China.Therefore,from northwest to southeast in China,the Qaidam Loess (sandy loess),the Loess Plateau Loess(typical loess),the Shandong Loess(clayey loess)and the Xiashu Loess in Zhenjiang(fine clayey loess),which are in zonal ranges,constitute the special extending sequence of spatial distribution of the Quaternary eolian deposition in China.They are the geological unity formed by the interaction of air earth system under the dry cold conditions during the Quaternary glacial epoch.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2001年第1期25-32,共8页
Marine Geology & Quaternary Geology
基金
国家自然科学基金! (495 710 71)
江苏省自然科学基金!(BK972 19)
南京大学现代分析中心测试基金资助项目
