黄河晋陕峡谷吉县段全新世古洪水平流沉积特征研究

Sedimentary characteristics of the slackwater deposits of Holocene extreme floods in the FJJ section in the Yellow River valley,Ji County

鉴别古洪水沉积物是古洪水水文学研究中最基本的任务。古洪水沉积物特征的研究对于识别古洪水沉积以及利用古洪水沉积物来恢复古洪水的水位,流量和发生规律都有十分重要的意义。通过对黄河晋陕峡谷吉县段流域深入调查,在黄河中游峡谷发现具有典型的古洪水平流沉积夹层的全新世黄土古土壤剖面。利用地貌学和第四纪地质学、沉积学,进而通过磁化率、粒度分析深入揭示了古洪水沉积物与风成黄土堆积物之间的主要区别。

Over the past two decades,analysis of slackwater sediments has become a widely accepted tool in palaeoflood research.The most important and basic question in palaeoflood study is ascertained the sediments of palaeoflood.This paper reports the identification of the palaeoflood slackwater sediments in the Jixian FJJ section in Huanghe River Valley in the Shaanxi Province and Shanxi Province. Since each flood units in slackwater sediments occur as couplets,we used Bartington susceptibility meter to discern the number of couplets as the organic rich deposits cause a magnetic susceptibility variation,and grain size analysis was undertaken to examine in sedimentary characteristic of slackwater deposits.There are abrupt changes in colour,grain size,and sedimentary type between the slackwater deposits and the loess.The clay in the slackwater deposits are much more than loess.Using palaeo-geography,sediment physiognomy,finding susceptibility and analysis of the sediment size.We can identity the palaeoflood slackwater sediments in the Holocene loess profile.