泾河泾阳段高河漫滩沉积元素与化合物指示的洪水事件

根据泾阳泾河高漫滩沉积剖面中128个样品的元素、化合物含量与粒度分析,研究了泾阳泾河高漫滩剖面沉积特征与洪水变化.结果表明,元素Ma,Ni,Cu,Zn,Ga,Pb,Ba,Rb,V和化合物Al2O3,Fe2O3,K2O含量在剖面各层中变化明显,分辨率高,能够清晰地指示洪水以及降水量的变化.JYa剖面分为18个沉积层,指示了18次大小不同的洪水和18个降水较多的年份.沉积物粒度细,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3Fe2O2,K2O含量高,元素Ba含量低,指示沉积时洪水强度小,洪水水位低,降雨量少.沉积物粒度粗,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3,Fe2O3,K2O含量低;元素Ba含量高,指示沉积时洪水强度大,洪水水位高,降雨量多.在这18次洪水事件中,在同一次洪水沉积层内形成了两个以上薄层的元素和化合物含量、粒度成分的微小变化,指示多数期次的洪水发生时期常有两个以上洪峰出现.泾阳泾河高漫滩第14,12,13,8,5,1层洪水沉积反映了泾河泾阳段全流域性的年降水量增加,且年降水量至少达到约800 mm.

Flood Events Indicated by Elements and Compounds of Sediment in the Jingyang Reach of Jinghe River

According to the analysis of elements,compounds,and grain size of 128 samples,we study the flood variation indicated by sediment in floodplain in the Jingyang reach of Jinghe River during deposit of floodplain. Results show that the contents of Mn,Ni,Cu,Zn,Ga,Pb,Ba,Rb,V,Al₂O₃,Fe₂O₃,and K₂O change obviously in the profile. Each component changes obviously in the entire profile,which can clearly reflect the variations of flood and precipitation with high resolving power. The profile may be divided into 18 sediment layers,indicating 18 flood events at different scales and 18 years with much precipitation. The finer grain size is,the higher contents of Mn,Ni,Cu,Zn,Ga,Pb,Rb,V,Al₂O₃,Fe₂O₃,and K₂O are and the lower content of Ba is,which indicates small flood intensity,low flood level,and less precipitation in deposition. In contrast,the coarser grain size is,the lower contents of Mn,Ni,Cu,Zn,Ga,Pb,Rb,V,Al2O3,Fe₂O₃,and K₂O are and the higher content of Ba is,which indicates high flood intensity,high flood level,and more precipitation at deposition. The small changes of two or more elements,compounds,and grain size in the thin layer formed in the same sediment layer in the 18 floods indicate two or more flood peaks frequently appeared in the period of most floods. Sediment in the 14th,12th,13th,8th,5th,and 1st layers in floodplain in the Jingyang reach of Jinghe River reflects that annual precipitation increases in the whole basin and annual rainfall is greater than 800 mm.