豫西北奥陶系马家沟组三段豹斑灰岩的生物潜穴成因及成岩演化

摘要

通过野外露头实地观测和室内薄片分析，对豫西北奥陶系马家沟组三段豹斑灰岩的发育特征及成因进行了研究。结果表明：研究区马家沟组三段豹斑灰岩中“豹斑”形态多样，形似生物潜穴，结合遗迹学特征分析，可将“豹斑”按其形态划分为Psilonichnus、Chnodrites、Thalassinoides、Helminthopsis及Planolites等5种生物潜穴类型，不同类型生物潜穴的出现主要受到沉积环境的制约；生物潜穴充填物按照其不同白云石化程度可被划分为泥晶白云石充填物及粉－细晶白云石充填物两种类型，其中泥晶白云石主要存在于Psilonichnus及Chnodrites两种潜穴中，而粉－细晶白云石则主要存在于Thalassinoides、Helminthopsis及Planolites之中；潜穴充填物的白云石化过程可被分为白云石化前的准备阶段、白云石的形成阶段及白云石的后期调整等三个阶段，不同潜穴的白云石化状态差异就是在此过程中形成的。%The development characteristics and origin of leopard limestone in the third member of Majiagou For-mation in Ordovician of north-western Henan Province were studied by using methods of outcrop observation and thin section analysis.The results show that the ‘leopard’can be divided into five types of biological burrows according to their morphological characteristics and ichnology,i.e.Psilonichnus,Chnodrites,Thalassinoides, Helminthopsis and Planolites.The emergence of different types of biological burrow was mainly restricted by sed-imentary environment.The burrow fillings can be divided into two types according to their different dolomitiza-tion degrees:(1 )micritic dolomite fillings,mainly exist in Psilonichnus and Chnodrites;(2)powder-fine crystal dolomite fillings,mainly exist in Thalassinoides,Helminthopsis and Planolites.The process of dolomitization can be divided three stages,i.e. the preparation stage before dolomitization,the formation stage of dolomites and the adjustment stage of dolomites,and the different dolomitization statuses of burrow fillings are formed in this process.