地理学报 ›› 2015, Vol. 70 ›› Issue (9): 1516-1525.doi: 10.11821/dlxb201509013

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河流纵剖面陡峭指数对庐山构造抬升的指示

王乃瑞(), 韩志勇(), 李徐生, 陈刚, 王先彦, 鹿化煜   

  1. 南京大学地理与海洋科学学院,南京 210023
  • 收稿日期:2015-06-24 修回日期:2015-07-16 出版日期:2015-09-20 发布日期:2015-09-20
  • 作者简介:

    作者简介:王乃瑞(1991-), 男, 山东济宁人, 硕士, 主要从事构造地貌研究。E-mail: nerrywang@qq.com

  • 基金资助:
    国家自然科学基金(J1210071, 40771023, 40971004)

Tectonic uplift of Mt. Lushan indicated by the steepness indices of the river longitudinal profiles

Nairui WANG(), Zhiyong HAN(), Xusheng LI, Gang CHEN, Xianyan WANG, Huayu LU   

  1. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210023, China
  • Received:2015-06-24 Revised:2015-07-16 Published:2015-09-20 Online:2015-09-20
  • Supported by:
    National Natural Science Foundation of China, No.J1210071, No.40771023, No.40971004

摘要:

庐山是位于江南造山带北缘的断块山,其抬升过程对于认识本区的构造演化至关重要。利用河流纵剖面的形态参数可以定量估算相对的构造抬升速率。基于5 m分辨率的DEM提取了庐山9条主要河流的纵剖面,依据坡度—面积图确定了裂点类型,结合地质图判别出裂点成因,并利用河流水力侵蚀模型计算了稳定态河段的陡峭指数以及凹曲度。结果显示,庐山的河流基本呈过渡态,以发育数量不等的裂点为标志;垂阶型裂点的形成主要与岩石强度不均一有关,而坡断型裂点是侵蚀基准面下降产生的。坡断型裂点以下的基岩河段具有较大的陡峭指数,表明庐山经历了从早期低抬升速率到晚期高抬升速率的转变。庐山受快速抬升影响的河段,陡峭指数具有南高北低的特点,主要是由于庐山整体抬升过程中南部、北部的抬升速率存在一定差异,亦可能是岩性不同造成的。

关键词: 庐山, 河流水力侵蚀模型, 陡峭指数, 构造抬升, 裂点

Abstract:

In this study, we extracted nine river profiles from a 5-m DEM of the Mt. Lushan region. Knickpoints of two types, namely the vertical-step knickpoint and the slope-break knickpoint, are recognized, and are compared with the geological settings to determine their origins. At the same time, we calculated the channel steepness index (ksn) and concavity (θ) of separated parts of these rivers, using the stream-power incision model. The results show that these rivers are almost in a transient state represented by the occurrence of knickpoints. The vertical-step knickpoints are related to inhomogeneous substrates and the slope-break knickpoints are ascribed to the lowering of the base level due to rapid mountain uplift. The parts of the rivers below the slope-break knickpoint have a relatively large ksn, which probably indicates a shift from low rate at early uplift to a later high rate. The steepness index in the south of the mountain is larger than that in the north, which might be induced by different uplift rates or substrates.

Key words: Lushan, stream-power incision model, normalized channel steepness index, tectonic uplift, knickpoint