几丁虫的反射率——早古生代有机岩石学的新前缘

根据对我国扬子地台中部奥陶纪几丁虫生物地层及其壳壁光性特征和反射率的研究，联系华南及塔里木盆地有关的资料，系统总结了我国奥陶纪、志留纪几丁虫生物组合序列的划分及其对比，探讨了几丁虫的光性特征。指出几丁虫在所切光面上具有各向同性的光性特征，只有反射率而无双反射率；在相同成熟度情况下，几丁虫的随机油浸反射率较笔石高，而较虫牙和疑源类低。通过对几丁虫反射率与同层或邻近层位中所测Ｉｃａ、笔石反射率，尤其是分散有机质红外光谱分析所获等效镜质组反射率的对比说明，几丁虫的随机反射率Ｒ０为１０４％～１７０％，＞１７％～３１％和＞３１％～４１％时，分别相当等效镜质组反射率（Ｒ０，ｅｑ）０９％～１３５％，＞１３５％～２２％和２２％～３０％，依次指示含几丁虫母岩有机质演化处于成熟、过成熟早期和过成熟晚期阶段。尽管这个对应关系还需要在今后研究中去进一步证实，但至少说明，几丁虫反射率随有机成熟度增加而增加，对于不含镜质组的晚志留世以前地层来讲，它们可以作为有机质成熟度的指示。

CHITINOZOAN REFLECTANCE:A FRONTIER IN EARLY PALEOZOIC ORGANIC PETROLOGY

Based on the systematic investigation of Ordovican and Silurian chitinozoan biostratigraphy and reflectance from central Yangtze Platform, China, in association with relevant data from South China and Tarim basin, this paper redefines Ordovician and Silurian chitinozoan assemblage succession of China and its correlation, and puts emphasis on discussion of chitinozoan optical properties and its reflectance. It is further indicated that chitinozoans exhibit optically isotropic property in polished section, having no bireflectance, the random reflectance of chitinozoans in oil immerssion is lower than that of graptolites, but higher than that of scolecondonts and acritarchs in same maturity. Based on the corresponding relationship of chitinozoan random reflectance with equivalent vitrinite reflectance evaluted by using graptolite reflectance, I ca , especially IR spectroscopic identification of dispersed organic matter from the same or adjacent horizon it is shown that the random reflectance of chitinozoan reflectances ( R 0%) at 1.04% —1.70%, >1.7%—3.1% and >3.1%—4.2% respectively corresponds to the equivalent vitrinite reflectance R 0,eq of 0.9%—1.35%, >1.35%—2.2% and >2.2%—3.0%. This corresponding relationship, without doubt, requires additional supporting evidence from future studies, but at least demonstrates that the reflectance of chitinozoans increases with increasing maturity and may be used as an indicator for organic maturity in the vitrinite free pre Late Silurian sedimentary rocks.