颍河上游褚河段古洪水事件及其沉积响应

Ancient Flood Events in Upstream Reaches of the Ying River and the Depositional Response

摘要: 通过对颍河上游禇河镇段一处典型的古洪水滞流沉积层剖面(SWD)的粒度、磁化率等指标进行综合研究，并结合野外特征描述，分析了该剖面理化特征，探讨了该地区发生洪水的次数。研究结果表明：1) 在YH-CH剖面粒度组成中以粉砂为优势粒径，含量介于47%~85%之间，平均含量为64.3%；粘粒含量较少，含量波动于3.2%~9.5%之间，平均为5.3%；砂级颗粒平均含量为17%；在累计频率曲线图上，B、C、D、E等层位偏左，SWD1和SWD2偏右；SWD1和SWD2分选较好且沉积颗粒较粗。2) 该剖面低频磁化率(X-lf)和高频磁化率(X-hf)具有相似的变化趋势，都呈现出B、C、D、E磁化率值相对较高，而SWD1与SWD2磁化率值相对较低，说明了SWD1和SWD2为典型的古洪水滞流沉积物。综合研究表明，YH-CH剖面记录两期古洪水事件，对应的剖面深度分别为60~80 cm、180~200 cm，其中第一期洪水较第二期洪水能量较高，携带的沉积物颗粒较粗。同时这些特征也为颍河上游的古洪水事件的识别标志提供参考。

Abstract: Based on the test of grain size and magnetic ability from typical flood slack water deposits (SWD) in the Chuhe site, in upstream reaches of the Ying River, coupled with filed description, we analyze its physicochemistry features and discuss the sedimentary characteristics when floods happen. The results show that: 1) in the grain size of YH-CH profile, silt that varies from 47% - 85% is the main constituent, and the average level is 64.3%; clay content is less, between 3.2% and 9.5%, and its average level is 5.3%. Average sand-size particles’ content is 17%; on the cumulative frequency cure, B, C, D, and E incline to the left, and however, SWD1 and SWD2 incline to the right. It is obvious that SWD1 and SWD2 are special ancient flood slack water sediments; 2) the section of low-frequency magnetic susceptibility (X-lf) is in line with high-frequency magnetic susceptibility (X-hf) broadly in a changing trend; the magnetic susceptibility value of B, C, D, and E is relatively high, and the magnetic susceptibility value of SWD1 and SWD2 is relatively low. According to the experimental analysis, we conclude that the profile recorded two kinds of flood. And the depth of the corresponding profiles respectively is from 60 to 80 cm and 180 to 200 cm; the energy of the first ancient flood that carried a lot of coarse matters is higher than that of the second ancient flood. In addition, the study of sedimentary characteristics provides the reference for the identification of ancient floods in upstream reaches of the Ying River.