Baltic provenance of top-Famennian siliciclastic material of the northern Rhenish Massif, Rhenohercynian zone of the Variscan orogen

Abstract

The provenance of top-Famennian sedimentary rocks linked to the Hangenberg Crisis from the northern Rhenish Massif (Germany) was investigated by the means of detrital zircon U-Pb geochronology. Based on the obtained age spectra, three main tectonothermal domains are recognized as possible sources: Paleo-and Mesoproterozoic (~ 2000-1000 Ma) units of Baltica and Early Paleozoic Caledonian orogen (~ 500-400 Ma). Our interpretation of the detritus having been derived from northern source areas, i.e., Baltica and the Scandinavian Caledonides, with a minor input of German-Polish (Rügen-Pomeranian) Caledonides, contradicts the traditional view that, during the Upper Devonian, the northern Rhenish Massif was supplied by detritus from the south. Complementary mineralogical, textural and geochemical analyses point to a derivation of the detritus of Drewer and Hangenberg Sandstones mainly from felsic, recycled continental crust. The elevated concentrations of Pb and Zn in the studied sections are a feature attributed to hydrothermal alteration related to the terminal Devonian synsedimentary volcanism or post-depositional Variscan deformation.

Reply to Comment by M.F. Pereira, J.B. Silva and C. Gama on “Baltic provenance of top-Famennian siliciclastic material of the northern Rhenish Massif, Rhenohercynian zone of the Variscan orogen, by Koltonik et al., International Journal of Earth Sciences (2018) 107:2645–2669”

“…The arguments presented do not challenge our work relying on the provenance analysis of detrital zircons from the Famennian (par)autochthonous sediments of the northern Rhenish Massif. We do not attempt to extrapolate the implications of our results to SW Iberia, a task that was clearly beyond the scope of our paper (Kołtonik et al 2018). However, we would like to reiterate that the structure and evolution of the Rhenohercynian zone cannot be fully understood without the concept of the Rhenohercynian Ocean, whose opening and demise had a critical impact on shaping the geological relationships across the external part of the northern Variscides.…”

“…At the end of Devonian, the Neoproterozoic Avalonian basement in the latter area was buried underneath Palaeozoic sediments (Franke and Dulce 2017;, and it was not available as a source of detritus even if an early Neoproterozoic succession was somewhere hidden in the Variscan northern foreland. Of course, it is still possible that detritus of Famennian clastic rocks under the northern Rhenish Massif was supplied from a remote source in Nova Scotia, but, using Occam's razor, it is more realistic to assume their derivation from nearby Baltica (Kołtonik et al 2018).…”

Review of Devonian-Carboniferous Boundary sections in the Rhenish Slate Mountains (Germany)

“…However, conodonts proved that the overall succession is much more complex, with siliciclastic sedimentation starting much earlier in the uppermost Famennian. The source of the material must have been on a topographic high to the N (Koltonik et al 2018), not on a Rhenish Island in the S, as proposed in former palaeogeographic reconstructions. The combined evidence from Gallwitz (1928), Koch et al (1970), andClausen et al (1989a) Trench 2, 54.6-73.5 m, two packages of micaceous sandstone, in the lower part up to 15 cm thick beds, interrupted by a ca.…”

“…For example, a new study will provide details of the currently best Rhenish DCB section at the Borkewehr near Wocklum (northern Sauerland). A palaeogeographical overview was given by Paproth et al (1986a), with recent updates by Koltonik et al (2018).…”