淮河上游全新世风成黄土—土壤物质来源研究

Source of the Holocene Aeolian Loess-Soil in the Upper Reaches of the Huaihe River

通过对淮河上游地区河南新郑全新世黄土—古土壤剖面磁化率和粒度的测量分析,揭示了淮河上游地区沙质黄土和古土壤的物质来源。该区黄土—古土壤磁化率明显低于黄土高原区,而粒度明显比黄土高原区粗,属于沙质黄土。通过两地区粒度分布的对比,揭示了它们有不同的粉尘源区,分属于不同的风成系统。淮河上游地区黄土是近源风尘沉积物,粉尘主要来源于孟津以东黄河冲积、洪积扇的松散河流沉积粉沙,实质是黄土高原水土流失的产物。黄河的频繁决口、改道、泛滥沉积为其提供了丰富的物源,其粗颗粒粉尘产生和搬运堆积的动力是东北风。淮河上游地区全新世早期粉尘是近源粗颗粒堆积,堆积速率可达18 6cm/ka,是黄土高原南部地区的2 3倍。

Analysis to the experiment results of the magnetic susceptibility and the grain size of loess-soil profile in the Holocene in Xinzheng City,the source of loess-soil in the upper reaches of the Huaihe River is revealed.Experimental tests showed that the magnetic susceptibility of loess-soil sequences in the upper reaches of the Huaihe River was much lower than that in the Loess Plateau,but the grain size was much thicker than that in the Loess Plateau; and that,the loess in the upper reaches of the Huaihe River belonged to sandy loess.The contrasting on grain size for these two regions revealed that there were different dust sources,which belonged to different dust transporting aeolian systems.The loess in the upper reaches of the Huaihe River was a wind blown deposition of near source,while the thicker dust mainly came from the loose river deposition at the Yellow River alluvial fan in the east of Mengjin,and secondary came from soil erosion of the Loess Plateau.A large number of substances were provided by the frequent breaching of dike and route-changing,overflowing of the Yellow River.The carrying and pilling up the thicker dust was mainly caused by North -East wind.It's founded that speed of pilling up of the dust was very fast in the Holocene in the upper reaches of the Huaihe River.The speed was 18.6 cm/ka,which was about 2.3 time as that in the southeast of the Loess Plateau.