安徽宣城第四纪网纹红土的磁组构特征及其意义

MAGNETIC FABRIC CHARACTERISTICS AND SIGNIFICANCE OF RETICULATE RED EARTH IN XUANCHENG PROFILE,ANHUI PROVINCE

安徽宣城第四纪网纹红土剖面黄棕色土层和网纹层的K、P、E、F、L、q等磁组构参数特征显示,i3>60°样品的磁组构特征有效降低了后期风化作用的影响,可近似代表黄棕色土层和网纹层的原生磁组构特征。黄棕色土层的原生磁组构特征显示它形成于沉积动力强度弱而稳定、事件沉积偶尔发生的沉积环境;该层磁组构参数的平均值及组合参数特征均与风成黄土-古土壤沉积的相应特征十分吻合,表明其原始沉积环境与风尘沉积环境一致,从而为黄棕色土层的风积成因提供了沉积动力特征上的证据。网纹层形成于沉积动力强度大、稳定性相对较差的沉积环境;该层的磁组构特征与风成沉积的相应特征差别显著,但与部分水成沉积的相应特征有近似之处,结合该层物质组成上的风成特性,初步推断网纹层可能为早期的风积物经后期水流改造的产物。

Magnetic fabric investigation of yellow-brown layer and reticulate layer of reticulate red earth section in Xuancheng, southern Anhui Province has been carried out and data of magnetic fabric parameters K,P,E,F,L and q of yellow-brown layer and reticulate layer are gained. The characteristics of the above parameters indicate that the original magnetic fabrics of the yellow-brown layer and reticulate layer have been recomposed by weathering in different ways, while the former seemed to be more seriously reworked. The original magnetic fabrics implicate that the yellow-brown layer was deposited in weak but stable force condition with event deposition happening occasionally. However, the reticulated layer was formed in strong and unstable force conditions. The characteristics of mean values （K, P, E, F, L and q） and collaborated parameters（F-L, P-q ） of yellow-brown layer are coincident with those of eolian loess-paleosol, indicating its eolian deposit formation. However, the characteristics of the corresponding values in the reticulated layer differ significantly from those of eolian deposit, but somewhat close to those of hydraulic deposit. It probably implicate that the reticulated layer has been recomposed by fluviation.