Upper Eifelian and Givetian (Middle Devonian) conodont sequence at Renanué (Aragonian Pyrenees, Spain): a relevant section for Givetian Chronostratigraphy

Abstract

ABSTRACT The study of 111 conodont samples has provided the first detailed biostratigraphical subdivision of the Renanué section ranging from the upper Eifelian ensensis Zone into the uppermost Givetian norrisi Zone. The conodont record supports the global threefold subdivision of the Givetian. The lower boundary of the Lower Givetian coincides with the lower boundary of the Givetian and is recognised in the uppermost 5 cm of Bed −8 with the entry of Polygnathus hemiansatus. The lower boundary of the Middle Givetian is identified in Bed 5 with the joint entry of P. varcus and P. rhenanus. Lack of Schmidtognathus precludes identification of the Upper Givetian lower boundary, but the conodont assemblage suggests its position around the lower part of Bed 55. Absence of Ancyrodella and other key taxa impeded precise identification of the Frasnian lower boundary and its earliest zones. Our lowest record of P. webbi seconds its global downwards range extension into the Upper Givetian. The uppermost local record of P. rhenanus might sustain the upward extension of its range into the latifossatus Zone.