Uppermost Famennian stratigraphy and facies development of the Reigern Quarry near Hachen (northern Rhenish Massif, Germany)

Abstract

As a contribution to the ongoing international revision of the Devonian/Carboniferous boundary, we present a bed-by-bed study of the Reigern Quarry in the northern Sauerland (Rhenish Massif, Germany), which is famous as an uppermost Famennian ammonoid locality. Currently exposed are ca. 2.5 m of strongly cyclic Wocklum Limestone, conformably overlain, but with a long hiatus (topmost Famennian to upper Tournaisian), by laminated radiolarites and a thin metabentonite of the Lower Carboniferous Hardt Formation. The nodular limestones are pelagic mud-wackestones with some sporadic occurrences of cephalopod float-rudstones. The exposed part of the Wocklum Limestone falls in the successive Bispathodus ultimus ultimus and Siphonodella (Eosiphonodella) praesulcata (s.l.) zones. It yielded two new Siphonodella (Eosiphonodella) species left in open nomenclature, Neopolygnathus communis aff. dentatus and the possibly stratigraphically relevant Bispathodus ultimus corradinii ssp. nov. The upper range of Palmatolepis gracilis semisigmoidalis is significantly expanded. The conodont faunas mostly belong to variants of the pelagic Palmatolepis-Bispathodus biofacies; but in the lower part of the succession, there is a new Neopolygnathus biofacies that previously has not been recorded from deeper-water, pre-Hangenberg Crisis strata. Neopolygnathus is interpreted as a palaeoecological generalist that variably blossomed in outer or inner shelf facies and after other conodont groups declined. The mostly loose ammonoid faunas comprise almost 30 taxa and fall mostly in the lower Wocklumian Kalloclymenia subarmata and Muessenbiaergia bisulcata zones (Upper Devonian = UD VI-A1/A2), which agrees with previous ammonoid-conodont correlations.