影响海陆交互相沉积物亮度的几个因素

Factors Influencing the Lightness of Paralic Sediments From Borehole LZ908 in the Southern Laizhou Bay

对中国北方莱州湾南岸钻孔上部54m海陆交互相沉积物的亮度进行研究,探讨其作为海陆交互相沉积物的环境指标的可行性,同时通过对比不同样品处理方式所得的亮度值探讨影响亮度的几个因素。测量分2次进行,分别使用Minolta CM-2002分光光度计针对柱状原样及Minolta CR400/410色差计针对风干研磨后的散样进行。研究结果表明,海陆交互相沉积物的亮度,尤其是经过风干处理后样品的亮度值,与碳酸钙含量及粒度两个古气候代用指标均具有显著相关关系,可以将其作为碳酸钙含量的替代指标应用于海陆交互相沉积物的环境演化研究。而亮度值与碳酸钙含量不一致性,可归因于沉积物中非碳酸钙组分的性质及含量。粒度与亮度的相关性显示,钻孔砂质沉积中含有的大量深色的有机质使得钻孔中粒度0～31μm的部分比例越高,亮度会越大,而粒度>31μm的部分比例越高,亮度会越小。2次亮度值的对比表明,水分、氧化作用及研磨是沉积物2次测量所得亮度值存在差异的主要原因。

The lightness of the paralic sediments collected from the top-54m of Borehole LZ908 taken from the southern coast of the Laizhou Bay was studied and several factors influencing the lightness of the sediments were discussed by comparing the lightness values obtained after different sample preparations.In addition,the feasibility for using the lightness as an environmental indicator of paralic sediments was also discussed.The measurements of lightness were performed twice,during which a Minolta CM-2002 spectrophotometer was used for measuring the original and fresh samples collected from the borehole and a Minolta CR400/410 system for air-dried and ground samples.The results indicate that the lightness values of the samples studied,especially those from the air-dried and grounded samples,show a prominent correlation to the calcium carbonate content and grain size which have been considered to be the proxies of palaoclimate,indicating that the lightness could be,as a proxy of calcium carbonate content,used for the study of the environment evolution of the paralic sediments.The inconsistency between the lightness values and the calcium carbonate contents may possibly be attributed to the properties and contents of non-carbonate components in the sediments.The correlation between lightness and grain size show that the higher the proportion of（31 μm in grain size,the bigger the lightness is,whereas the higher the proportion of（31 μm is,the smaller the lightness is.It can be seen from the twice measurements that dehydration,oxidation and grinding may possibly be the main reasons for the differences in the lightness varieties.