Upper Frasnian conodont biostratigraphy of the Noravank section (Central Armenia)

Abstract

In order to distinguish the standard conodont biozones around the Late Frasnian critical interval in the Lesser Caucasus, the Noravank section is examined here. Our study yielded an abundant and relatively diverse conodont fauna, representative of the icriodid–polygnathid biofacies. Most notably, the carbonate interval situated at the lower part of the studied section contains Icriodus alternatus alternatus, I. alternatus helmsi, I. expansus, I. excavatus, Polygnathus webbi, P. aequalis, P. politus and P. brevilaminus. This assemblage suggests a Late Frasnian age and correlates with the rhenana conodont Zone sensu lato, thereby providing a chronostratigraphic constraint for the local brachiopod Zone Ripidiorhynchus gnishikensis–Angustisulcispirifer arakelyani. Conodonts obtained by some limestone intercalations within the overlying siliciclastic interval include I. iowaensis iowaensis and P. webbi, which constrain its age to the linguiformis Zone.