The Devonian-Carboniferous transition at Borkewehr near Wocklum (northern Rhenish Massif, Germany) – a potential GSSP section

Abstract The Borkewehr section near Balve at the southeastern end of Remscheid-Altena Anticline is currently best and most complete Devonian/Carboniferous Boundary (DCB) succession Rhenish Massif, Germany. Based on a multidisciplinary approach, focusing refined conodont ammonoid biostratigraphy, microfacies analyses, sequence stratigraphy, carbon isotopes (C org C carb ), trace element geochemistry, including REE data, cyclostratigraphy, proposed as candidate for new basal Carboniferous GSSP. represents pelagic “seamount” setting. It spans upper Famennian to lower Viséan, with condensed development lithostratigraphic units sedimentary sequences. type-section oxic strongly cyclic, fossiliferous Wocklum Limestone important uppermost index species. First Appearance Datum (FAD) Protognathodus kockeli s.str., in phylogenetic from ancestral Pr. semikockeli n. sp., future GSSP level. This FAD sandwiched between many other marker levels global correlation. Below are, base top, transgressive least partly anoxic Hangenberg Black Shale (base Lower Crisis Interval), Regression (onset siltstones Middle level maximum regression, indicated by Zr/Al values, initial transgression Upper Interval, marked re-onset carbonate deposition. Above follow locally cryptogenic Siphonodella (Eosiphonodella) sulcata s.l. post-Crisis Interval (Hangenberg Limestone), associated biofacies shift, Si. (Eo.) bransoni , and, much higher, sharp Alum Event classical middle Tournaisian. significance greatly enlarged its precise correlation numerous DCB sections that provide additional data faunas, geochronological ages, magnetic susceptibility. suggest changes weathering intensity, based Rb/K K/Al trends, Milankovitch cyclicity climate Crisis. local extinction rate top lies 57 % while there are no survivors ammonoids, trilobites, or deep-water corals. Positive isotopic shifts decoupled, which suggests complex underlying processes not yet understood.