Provenance of exotic Ordovician and Devonian sedimentary rock units from the Rhenish Massif (Central European Variscides, Germany)

Abstract Within the Rhenohercynian Zone of the Central European Variscides, the southeastern Rhenish Massif (Germany) contains Paleozoic greywackes and sandstones of uncertain origin and correlation. Herein, detrital zircons from a selection of these rocks are analysed for their U-Pb ages and Lu-Hf values: the Late Ordovician “Andreasteich Quartzite” and the Early Devonian “Dalmanites Sandstone” from the Lindener Mark nappe as well as the “Erbsloch Greywacke” from its type locality in the southern Kellerwald. In addition, the latter greywacke and the “Damm-Muhle Greywacke” from the Steinhorn nappe in the Lahn-Dill area were investigated petrographically. We present a data set for U-Pb ages of 542 detrital zircon grains together with Lu-Hf isotope systematics of 202 dated zircons. U-Pb zircon ages, eHf ratios, and model ages point to an exotic provenance for the sedimentary rock units relative to the Rhenohercynian Zone. The rocks were thrust as top-NW nappe complexes onto the southern Rhenohercynian Zone during Laurussia-Gondwana-collision following the closure of the Rheic Ocean. Potential source areas are identified in the Armorican (Cadomian) part of the Variscan orogen. In terms of paleogeography, the sedimentary rocks were most likely deposited along the southern margin of the Rheic Ocean, presumably on a shelf marginal to the Saxo-Thuringian Zone. This provenance is consistent with the presence of Devonian faunal elements in respect to the surrounding Rhenohercynian Zone and have northern Gondwana biogeographic affinity. Thin section analysis in conjunction with provenance data give rise to the interpretation that andesitic volcanoes existed in the southern Rheic Ocean at the time of sedimentation. Recent publications about revised biostratigraphy and paleobiogeography of Lower Devonian provide grounds for discussion about the age of these sediments.