黄土地区河谷古洪水平流沉积物特征研究

The Study on Characteristics of Slackwater Deposits of Palaeoflood Sedimentary in the Loess Regions

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。在漆水河和湋河交汇的二级阶地上沉积了比较明显的古洪水沉积层。对该剖面进行磁化率、烧失量、碳酸钙、粒度指标的测定。并将古洪水沉积层与黄土堆积层进行对比发现:古洪水淤积层除了第三平流沉积层外,其它每个平流层指标数值都介于黄土堆积古土壤、马兰黄土之间。表明古洪水堆积层有较弱的成壤作用发生。这些指标揭示了古洪水堆积与黄土堆积之间的区别。

Analysis of slackwater sediments has become a widely accepted in palaeoflood research. The identification the palaeoflood deposits are important for the study of palaeoflood. This paper reports the identification of the palaeoflood slaekwater sediments in the Holocene loess profile in the loess region. We measured the magnetic susceptibility, clay content, CaCO3 and clay/silt ratio, in the HXZ-E profile, Qishuihe River Valley and compared with the loess accumulation. The results show that indexes in the palaeoflood deposits except the third deposit are between the soil and the loess accumulation. These indicate the palaeoflood deposits have the weak pedogenic. Through the research of these indexes we can identity the palaeoflood slaekwater sediments from the loess accumulation. This research result is not only practical to the flood control, water resources exploitation and eco-environmental construction for Yangling, a well-known agricultural and high-tech city in River Basin, but seientifiely significant to the comprehensive improvement of the eco-environment of the river basin.