Latest Devonian conodonts from an olistolith in the northern part of the Góry Bardzkie, West Sudetes

Abstract

Latest Devonian conodonts have been recovered from siliceous rock at Bardo Śląskie, Góry Bardzkie (Mts), West Sudetes. The exposure in the Nysa Kłodzka river cut consists of several undisturbed intervals, separated by zones of fault breccia, interpreted as one large olistolith of Devonian rock embedded in a surrounding Lower Carboniferous graywacke. The siliceous rock shows signs of very low-grade contact metamorphism (300-360°C; conodont CAI = 5) attributed to the late Carboniferous granite intrusion. They represent intervals from Mid- to probably Late-expansa Zone, Mid-expansa to the Early-praesulcata Zones and undivided praesulcata-Zone, all suggesting the latest Famennian age for the siliceous host rocks, which appear the youngest Devonian sediments paleontologically documented to date in the allochthonous domain of the Góry Bardzkie. Palmatolepis and Polygnathus are the most frequent genera. The two genera are believed to indicate the deepest pelagic environment of the late Devonian sea. Both the biofacies and lithofacies of the investigated sediments strongly suggest their distal, deep-water basinal origin. The presence of the open-marine pelagic sediments in the uppermost Famennian seems to imply a continuous sedimentation rather, than a break at the Devonian-Carboniferous boundary in the Góry Bardzkie allochthonous domain.