环境敏感因子在威海湾沉积环境中的应用比较

Application of Environmentally Sensitive Factors in Bay Sedimentary Environments

环境敏感因子是沉积环境演化研究中的重要参数,其提取方法有多种,不同方法在海湾内应用成果相对较少。文章根据山东半岛威海湾WH-05岩心(钻探深度18.2 m)高分辨率(2 cm)粒度分析结果,采用基本端元模拟算法(BasEMMA)、粒级—标准偏差法和粒级旋转主成分分析法(V-PCA)提取了环境敏感因子,结合AMS14C数据,对不同方法提取的环境敏感因子进行了对比分析,探讨了其对季风强度变化的响应关系。结果表明:8.4 ka B.P.以来威海湾沉积物类型均为粉砂,粉砂含量为主、黏土含量次之、砂含量较少,以跳跃组分为主,悬浮组分次之。BasEMMA和粒级—标准偏差法提取的3个敏感粒级范围(2.6~11.0μm、31.3~63.4μm、256.9~500.0μm)总体一致,能较好地反映东亚季风长周期变化事件(8.4~6.5 ka B.P.东亚季风强度减弱;6.5 ka B.P.至今东亚季风强度增强);V-PCA提取的环境敏感因子,能较好地反映东亚季风短周期变化事件(如明清小冰期、西汉小冰期事件等)。以上三种方法提取的环境敏感因子指示了研究区气候变化,对研究区沉积环境具有较好的指示作用。

Environmentally sensitive factors are an important parameter in the study of the evolution of sedimentary environments.The methods of extracting environmentally sensitive factors are diverse but there are relatively few reported application results of the different methods in bay environments.Based on high-resolution(2 cm) particle size analysis for core WH-05 in Weihai Bay,Shandong Peninsula(drilling depth 18.2 m),three methods were used(basic end-member model algorithm(BasEMMA),grain-size standard deviation method,and varimax-rotated principal component analysis(V-PCA)) to extract environmentally sensitive data.These factors are compared and analyzed,and their response to the change of monsoon intensity is discussed.The results show that since 8.4 ka B.P.,the sediments in Weihai Bay have all contained silt,with predominant silt content,secondly clay content,and least sand content.The silt component is dominant,and the suspended component is next in importance.The three sensitive grain size ranges(2.6-11.0,31.3-63.4,256.9-500.0 μm) extracted by BasEMMA and the grain-size standard deviation method are consistent on the whole,and reflect well the long-period East Asian Monsoon variation events(from 8.4 ka B.P.to 6.5 ka B.P.the intensity of the East Asian Monsoon weakened;from 6.5 ka B.P.to the present time it has strengthened).The environmentally sensitive factors extracted by V-PCA better reflect the short-term variation of East Asian Monsoon events(e.g.,the Ming and Qing Little Ice Age and the Xi Han Little Ice Age).The environmentally sensitive factors extracted by the above three methods indicate the climate changes in the study area and are a good indicator of the sedimentary environment in the study area.