| 汉江上游晏家棚段古洪水沉积物粒度空间分布特征 |
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| 引用本文： | 郑树伟,庞奖励,黄春长,查小春,李欣.汉江上游晏家棚段古洪水沉积物粒度空间分布特征[J].地理科学进展,2014,33(6):799-806. |
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| 作者姓名： | 郑树伟 庞奖励 黄春长 查小春 李欣 |
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| 作者单位： | 陕西师范大学旅游与环境学院, 西安 710062 |
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| 基金项目： | 国家自然科学基金项目(41271108,41030637,41371029);中央高校基本科研费项目(GK201301003) |
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| 摘 要： | 对汉江上游流域进行了深入的地层学及地貌学调查，在郧县河段河流一级阶地上覆黄土-古土壤沉积剖面中发现了典型的古洪水沉积层。对其进行了系统采样和粒度分析，结果表明，古洪水沉积层的粒度在空间上有明显的变化。水平方向上，相同层位的粒度自然分布曲线、概率累积曲线和平均粒径基本相同；垂直方向上，从上向下粒度自然分布曲线、概率累积曲线和平均粒径明显不同，粒径逐渐变细。水平方向上的粒度特征说明，古洪水同层位的样品可以相互替代；垂直方向上的变化与前人在泾河以及渭河流域等地研究发现的古洪水沉积层呈从下向上逐渐变细的沉积模式不同，说明古洪水沉积层的沉积模式并非只有一种，而是存在多种沉积模式，这种变化可能与洪水过程有关。
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| 关 键 词： | 古洪水沉积物 汉江上游 空间变化 粒度 |
| 收稿时间： | 2013-12-01 |
| 修稿时间： | 2014-03-01 |
Spatial variation of palaeoflood deposits at Yanjiapeng site in the upper reach of the Han River |
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| ZHENG Shuwei,PANG Jiangli,HUANG Chunchang,ZHA Xiaochun,LI Xin.Spatial variation of palaeoflood deposits at Yanjiapeng site in the upper reach of the Han River[J].Progress in Geography,2014,33(6):799-806. |
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| Authors: | ZHENG Shuwei PANG Jiangli HUANG Chunchang ZHA Xiaochun LI Xin |
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| Affiliation: | College of Tourism and Environment, Shaanxi Normal University, Xi'an 710062, China |
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| Abstract: | Through the stratigraphy and geomorphology investigation along the upper reach of the Han River, a loess-soil profile recorded palaeoflood slack-water deposits (SWD) was found at the riverbank near the Yanjiapeng site. This profile (YJP) was examined in great details in the field. The palaeoflood slack-water deposits samples were collected systematically and the grain size of the samples was analyzed in the laboratory. Results indicate that the grain size of the palaeoflood slack-water deposits shows a significant change in space. In the horizontal direction, grain size distribution, cumulative probability distribution and average grain size are the same in the same layer. In the top samples, the content of clay (<2 μm) is between 2.46%-2.97%, the content of silt (2-63 μm) is between 33.80%-44.50%, and the content of sand-sized particles (>63 μm) is between 52.66%-63.64%. The grain size distribution curves of these deposits are consistent in the same layer. In the vertical direction, however, grain size distribution, cumulative probability distribution and average grain size vary, and the grain size becomes smaller down from the top—the grain size distribution curves shift to the left gradually. The particle size of the peak position shows the following feature: top samples > middle samples > bottom samples. Some previous studies indicate that in the vertical direction the grain size of palaeoflood slack-water deposits becomes larger down from the top in the Wei River and Jing River. The results of this study at the YJP site in the upper reach of the Han River proved that the spatial variation of palaeoflood slack-water deposits has different forms. Similar grain size in the same layer indicates that the hydrodynamic force was basically the same in the horizontal direction and this result is good for sample collection in the field. The change of grain size in the vertical direction indicates that the hydrodynamic force was different and the reasons for this change may be related to the temporary river damming during the floods or the gradual built-up and quick withdrawal cycles of the palaeofloods. Samples should be collected layer by layer in the field study of grain size of palaeoflood slack-water deposits. If the palaeoflood slack-water deposits pinch out point cannot be identified in the field, grain size of palaeoflood slack-water deposits pinch out point of the same layer at close proximity can be used instead. |
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| Keywords: | grain size palaeoflood SWD spatial variation upper Han River |
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