Abstract
Thirty Devonian-Carboniferous Boundary sections of the Rhenish Slate Mountains and adjacent subsurface areas are reviewed with respect to litho-, event, conodont, ammonoid, sequence, and chemostratigraphy. In the interval from the base of the uppermost Famennian (Wocklum Beds, Wocklumian) to the base of the middle Tournaisian (base Lower Alum Shale), 11 conodont and 16 ammonoid (sub)zones are distinguished. The terminology of the Hangenberg Crisis Interval is refined, with an overall regressive Crisis Prelude below the main Hangenberg Extinction, which defines the base of the transgressive Lower Crisis Interval (Hangenberg Black Shale). The glacigenic and regressive Middle Crisis Interval (Hangenberg Shale/Sandstone) is followed by the overall transgressive Upper Crisis Interval that can be subdivided into three parts (I to III) with the help of conodont stratigraphy (upper costatus-kockeli Interregnum = upper ckI, Protognathodus kockeli Zone, and lower part of Siphonodella (Eosiphonodella) sulcata s.l./Pr. kuehni Zone). Protognathodus kockeli includes currently a wide range of forms, which variabilities and precise ranges need to be established before a precise GSSP level should be selected. Returning to its original definition, the former Upper duplicata Zone is re-named as Siphonodella (S.) mehli Zone. It replaces the S. (S.) jii Zone, which is hampered by taxonomic complications. The S. (S.) quadruplicata Zone of Ji (1985) is hardly supported by Rhenish data. The entry of typical S. (S.) lobata (M1) characterises an upper subdivision (subzone) of the S. (S.) sandbergi Zone; the new S. (S.) lobata M2 enters much earlier within the S. (S.) mehli Zone. The ammonoid-defined base of the Wocklum-Stufe (Upper Devonian = UD VI) begins with the Linguaclymenia similis Zone (UD VI-A1). The oldest S. (Eosiphonodella) enter within the Muessenbiaergia bisulcata Zone (UD VI-A2). The traditional Parawocklumeria paradoxa Zone of Schindewolf (1937) is divided into successive P. paprothae (VI-C1), P. paradoxa (VI-C2), and Mayneoceras nucleus (VI-C3) Subzones. In the lower Tournaisian (Lower Carboniferous = LC I), the Gattendorfia subinvoluta Zone is subdivided into G. subinvoluta (LC I-A2) and “Eocanites” nodosus (LC I-A3) Subzones. The Paprothites dorsoplanus Zone (LC I-B) can be divided into Pap. dorsoplanus (LC I-B1) and Paragattendorfia sphaeroides (LC I-B2) Subzones. Potential subdivisions of the Pseudarietites westfalicus (LC I-C) and Parag. patens Zones (LC I-D) are less distinctive. The unfossiliferous or argillaceous upper part of the Hangenberg Limestone and the overlying Lower Alum Shale Event Interval remain regionally unzoned for ammonoids.
Highlights
The Rhenish Slate Mountains, especially the northern and eastern Sauerland in the east of the river Rhine, are the most important of the classical regions for the study of the Devonian-Carboniferous Boundary (DCB) and of the global mass extinction interval that is known as Hangenberg Crisis (e.g. Kaiser et al 2015)
The regional ckI conodont record is very poor, with the exception of some limestone nodules from near its top at Drewer (Bed 97, Korn et al 1994b). They yielded an assemblage with Pr. meischneri, Pr. collinsoni, and Neo. communis communis, which are common in ckI faunas of many other regions
Based on direct co-occurrences in the Graz Palaeozoic and Carnic Alps, Kaiser et al (2019) confirmed the usefulness of Pr. kuehni as an alternative index species for the S. (Eo.) sulcata (s.l.) Zone. This is especially important for the majority of sections, where siphonodellids are absent in the Upper Crisis Interval
Summary
The Rhenish Slate Mountains, especially the northern and eastern Sauerland in the east of the river Rhine, are the most important of the classical regions for the study of the Devonian-Carboniferous Boundary (DCB) and of the global mass extinction interval that is known as Hangenberg Crisis (e.g. Kaiser et al 2015). Pseudopolygnathus marburgensis trigonicus seems to enter first (base of Wocklum Limestone at Oberrödinghausen, Schindewolf-Bed 23, Bed 181b of Sacher 2016; Sample 11 of Eickhoff 1973), followed by Pa. gracilis gonioclymeniae and Br. suprema at the level of “Sphenoclymenia” cf brevispina (Oberrödinghausen, Schindewolf-Bed 22, Kürschner et al 1993; Bed 185b of Sacher 2016), and by the name-giving zonal species (Müssenberg, Bed 80, Luppold et al 1994; Oberrödinghausen, Schindewolf-Bed 20 = Bed 191b of Sacher 2016). As outlined by Tragelehn (2010), Becker et al (2013), and Söte et al (2017), there are early relatives of Siphonodella, which represent two different genera These “siphonodelloids” have Polygnathus-type upper platforms, for example as in Po. inornatus and Po. symmetricus, but nonpolygnathid, extended basal cavities. Reference sections: Drewer (Beds 94–97); conodont-free Hangenberg Black Shale to Hangenberg Sandstone of other sections
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