洛阳盆地全新世特大洪水平流沉积物判别研究

文中基于详细的野外考察,在洛阳盆地汉魏故城遗址邻近河岸选择了YWC剖面,对剖面进行了磁化率、粒度和>0.1mm粒级百分含量等环境代用指标的室内实验分析和测定。通过野外沉积特征识别、室内粒度分析,准确判定了YWC剖面中洛河古洪水平流沉积层,发现YWC剖面记录了10次晚全新世特大洪水事件。YWC剖面中出现多个"古洪水平流沉积层-风吹沙层"互层,其中的平流沉积层为古洪水平流沉积物,风吹沙层则是洪水间歇期当地盛行的东北风搬运的河床沙在阶地上堆积的产物。平流沉积层与风吹沙层在YWC剖面的多次交替,反映出洛阳盆地晚全新世时期气候、环境系统的剧烈波动和恶化,东北季风强盛和古洪水事件的频繁发生。

Determination of the paleofloods slackwater deposits of the Holocene extreme floods in the Luoyang Basin

Based on detailed field investigation,one Holocene paleoflood profile YWC was sampled and studied by the proxy climatic data of magnetic susceptibility、particle-size distribution and >0.1mm% in laboratory.Through field sedimentary feature recognition,indoor particle size characteristics analysis and discriminant of mathematical formulas,it is determined that the YWC profile is Holocene slackwater flood deposits profile.The experimental data show that 10 Holocene paleoflood events were recorded in the following layers in YWC profile.We found many sandstorms activities in Luohe River Valley during the period of extreme flood intermittent which formed "aeolian fine sand layers" through field observations and laboratory analysis of sedimentary features.There are several "interbedded flood slacking deposits-aeolian fine sand layers" in YWC profile,the flood slacking layers are palaeoflood slacking deposits and the aeolian fine sand layers were carried by the NE direct wind.The "interbedded slack deposit-aeolian fine sand layers" indicate that the abrupt deterioration and fluctuation of climate and environment system,stronger NE direct wind and frequent paleofloods events in this region in Holocene.