The Devonian–Carboniferous boundary in the Carnic Alps (Austria and Italy)

Abstract

In the Carnic Alps there are four sections exposing rocks across the Devonian–Carboniferous boundary: the Grune Schneid and the Kronhofgraben sections in Austria, the Plan di Zermula A and the Sentiero per Cresta Verde sections in Italy. All of them are mainly composed of limestone and span from the late Famennian through the Tournaisian. In the Kronhofgraben and Plan di Zermula A sections, the limestone sedimentation is interrupted by black shales interpreted as equivalent of the Hangenberg Black Shales. The Grune Schneid and the Sentiero per Cresta Verde sections are two of the few sections worldwide, where the calcareous sedimentation is continuous. The main extinction event registered at the end of the Devonian is testified not only in the sections where the calcareous sedimentation was replaced by black shales sedimentation but also in the Grune Schneid and in the Sentiero per Cresta Verde sections. Data on conodont biostratigraphy and biofacies, the content in ammonoids, and trilobites and geochemistry patterns from all sections are here summarised and reviewed. These data-set allow to conclude that the four Carnic Alps sections positively test the suitability of the timeline proposed by the DCB working group for the definition of the revised Devonian–Carboniferous boundary.