The Cruziana ichnofacies in the lower member of the Bisericani Formation (Easthern Carpathians, Romania)

A 7 m sedimentary succession of the lower member of the Bisericani Formation from the Vrancea Nappe (Bistrița Half-window) was studied by means of sedimentary facies analysis and ichnological methods. The peculiar heterolithic deposits were accumulated by gravity flows, traction, and pelagic and hemipelagic fallout. They contain mainly hypichnial, endichnial, and rarely epichnial trace fossils, several of them being identified at ichnogenus or ichnospecies levels, such as: Chondrites, Avetoichnus luisae, Planolites, Lockeia, Thalassinoides, and Rhizocorallium commune. Ethologically, they can be included in fodinichnia, domichnia, and supposedly agrichnia (Avetoichnus luisae) categories, representing a part of the Cruziana ichnofacies. Based on combined sedimentary facies and ichnologic analysis, the depositional system of the studied section is interpreted as an offshore-transition one characterized by tempestites, favorable for the Cruziana ichnofacies development.