锁阳城镇东南部雅丹沉积物粒度特征及环境意义

Grain-size characteristics and environmental significance of long ridge shaped Yardangs in the southeast Suoyang town,China

雅丹地貌是地球表面成因最复杂的地貌之一,长期以来备受关注。以锁阳城镇东南部长垄状雅丹为例,对其沉积物粒度特征进行分析研究。结果表明:雅丹沉积物以粉沙组为主,其次为黏粒组、沙粒组。自然频率曲线呈单峰、不对称及近对称双峰分布,其主次峰均位于粉沙粒级和沙粒级,概率累积曲线呈4~5段式,蠕移方式仅出现在平均粒径较粗层位。平均粒径主要为粉沙粒级,分选整体差,偏度以近对称及正偏为主,峰度为中等、窄和宽型。粒度参数间无明显关系,但在垂直剖面上有一定规律。平均粒径较粗层位沉积物的来源不单一,搬运方式及沉积动力过程复杂,较细层位反之。沉积环境以河湖相为主,风力作用在雅丹地层后期形成过程中占主要地位。

Yardang landform is one of the most incomprehensible aeolian erosion landforms on the earth’s surface,and has attracted much attention for a long time.Taking the typical long ridge shaped Yardangs in the southeast of Suoyang town as an example,the grain size characteristics of the sediments in the profile were analyzed.The results indicated that:The grain size components of the deposits are silt sand,followed by clay and sand.The natural frequency curves of grain size mainly present unimodal,near symmetrical and asymmetric bimodal distribution.The main peak and secondary peaks of the bimodal distribution curves appear in silt and sand fraction,respectively.The cumulative probability curves of grain size are mainly four-stage and five-stage,and creep only appears in the layer with coarse particles.The mean particle size of the deposits is mainly silt,the standard deviation is poor as a whole;the skewness varies is mainly near symmetric and positive partial,and the kurtosis is mainly medium,narrow and wide.Grain size parameters show some rules in the vertical profile.However,there are no obvious linear relationship among the grain size parameters of sediments.The source of the sediments in the coarser layers is not single,and the transportation manner and sedimentary dynamic process are complex,while that in the finer layers is the opposite.The formation environment of the sediments is complex,but the main sedimentary deposits are formed in Fluvial-lacustrine environment.Aeolian power is the main reason for the later formation of Yardang landform.