哈尔滨黄山黄土粒度特征及其对成因的指示

Grain-Size Characteristics and Genesis of the Huangshan Loess in Songnen Plain Area

哈尔滨黄山黄土是东北地区黄土沉积的典型代表,其成因研究是恢复东北地区古气候和古环境的基础.为探讨松嫩平原地区中更新世晚期黄土成因问题,对具代表性的哈尔滨黄山黄土剖面进行系统、高分辨率的粒度和磁化率特征分析,并与哈尔滨现代沙尘沉降物、黄土高原典型黄土-古土壤、现代河流沉积物及大连市滨海黄土粒度特征进行对比.结果显示：黄山黄土粉砂级（10~50μm）颗粒和黏土颗粒（〈5μm）的平均含量分别是43.86%（主众数粒组）和23.40%（次众数粒组）;各粒度参数的平均值为：分选系数标准偏差σ=1.83、平均粒径Mz=6.25φ、中值粒径Md=5.89φ、偏度SK=0.21、峰态KG=0.86、中值粒径Kd=2.01;粒度频率曲线以双峰态分布为主,且主峰突出;岩性三角投影图、粒度象（C-M图、L-M图、A-M图）投影图及粒度参数（Mz-σ、Mz-SK、Mz-KG）散点投影图与风成沉积物基本一致,但与河流沉积物差异明显;判别函数Y〈0.基于以上粒度特征分析表明哈尔滨黄山黄土为典型的风成成因.

Huangshan Loess makes a typical example of Northeast China＇s loess deposition,studying its genesis is the key to reconstruction of both paleoclimate and paleoenvironment of Northeast China.A high resolution and systematic grain size analysis is carried out on ＂Huangshan Loess＂ in Harbin area,and the origin of ＂Huangshan Loess＂ is discussed in this paper in comparison with many other types of sediment including the modern dust deposition in Harbin area,the loess-palaeosol distributed over the Loess Plateau,the fluvial sediment and Qidingshan Loess in Dalian.The results show that：the 10-50μm partial group is the ＂dominant group＂ of the ＂Huangshan Loess＂ whereas the content of〈5μm partials occupies 23.40%,which is more than the average content of 〉50μm and 5-10μm particals,corresponding with the composition characteristic of typical eolian loess;The grain-size frequency distribution presents even-number peak and each of these features of grain size parameters are characterized by the atmospheric dust,the average of theσ,SK,KG,Kd,Mz,Mdis 1.83,0.21,0.86,2.01,6.25φ,5.89φ,respectively;Clay-silt-sand triangular plots of ＂Huangshan Loess＂ indicate that it belongs to clayey silt.C-M,L-M,A-M charts and statistical indices of grain size distribution share similarities with various aeolian sediments while obviously differ from fluvial sediments.No one discriminant analysis results is of positive value,which confirms that the＂Huangshan Loess＂is of the atmospheric sediment just like the aeolian origin of the loess-palaeosol in the Chinese plateau.