毛乌素沙地北缘苏贝淖湖滨沉积物磁化率与粒度组份的相关性研究

Correlation between the Content of Different Grain Size and Magnetic Susceptibility of SBN Lakeshore Section in Northern Edge of Muus Desert

以苏贝淖湖滨剖面沉积物为例,研究了沉积物磁化率与粒度的变化特征;并分析了各粒级组份与磁化率大小变化的相关关系。探讨沉积物磁性矿物的可能来源及富集状态,揭示它们在干旱区湖泊沉积物中所反映的古环境信息。结果显示:1沉积物磁化率和粒度自下而上分别经历了由低到高、由细到粗的总体变化趋势,代表了一种由湖滨浅湖相到风成沉积相过渡的沉积环境;沉积物整体粒径较粗,主要为砂(>63μm)和粉砂[(4~63)μm],二者的平均含量之和达到99.04%,剖面风成沉积物与现代风成沙的粒度曲线变化具有很好的一致性;2磁化率与砂粒级的颗粒含量呈正相关,而与粉砂和黏土无明显相关关系或呈负相关,说明磁性矿物主要赋存在砂粒级颗粒中,主要原因是沉积物中的磁性矿物以外源为主;3沉积物高磁化率值对应较粗的沉积物颗粒,指示湖区风沙活动较强,气候干旱;低磁化率值对应较细的沉积物颗粒,反映湖区环境相对较湿润。

In order to obtain the environmental change information and magnetic mineral sources, the samples of different lithology from the cores obtained at the SBN lakeside for magnetic susceptibility and grain size studies was choosed. Results show that the magnetic susceptibility in vertical from deep to shallow location with a variation of low to high, and the grain size changes from fineness to coarseness, which represents a sedimentary environment from shore meare facies to aeolian sedimentary facies. The grain size of sediment is coarse as a whole and the main materials are sand （ 〉 63 p,m） and silt [ （ 4 - 63 ） p,m ] and there average content is 99.04%. The grain-size change of eolian deposits and modem eolian sand have a good consistency. Magnetic susceptibility and sand fraction are positively correlated with each other which suggest that the magnetic mineral is mainly enriched in fractions of 〉 63 t^m, and the main reason is that magnetic mineral of sediment is primarily exogenous. The high magnetic sus- ceptibility corresponds to the coarser sediment particles which indicates strong sandstorm activities and dry climate, nevertheless the low magnetic susceptibility corresponds to the finer sediment particles which reflect the weather is relatively wet at Subei Nut Basin.