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

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.

The Hushoot Shiveetiin gol section (Baruunhuurai Terrane, Mongolia): sedimentology and facies from a Late Devonian island arc setting

A Late Devonian to (?)Early Mississippian section at Hushoot Shiveetiin gol in the Baruunhuurai Terrane of the Central Asian Orogenic Belt (CAOB) exposes large parts of cyclic Famennian shallow-water siliciclastic shelf deposits composed of siltstones, sandstones, shales, volcaniclastics, and intercalated autochthonous carbonates. The youngest part of the section, possibly Early Mississippian, is represented by arkosic sandstones with large plant remains. The facies reflects a range from shallow-intertidal to outer ramp settings. In terms of conodont stratigraphy, the Hushoot Shiveetiin gol section ranges from the Palmatolepis minuta minuta Biozone to at least the Palmatolepis rugosa trachytera Biozone. Hiatuses of several conodont biozones occur due to the facies setting (erosion and reworked sediments which are recognized by reworked conodonts) rather than thrusting or folding. The environmental setting was characterized by coeval subaerial volcanism resulting in numerous pyroclastic deposits. The depositional environments and intense volcanic activity at the Hushoot Shiveetiin gol section limited the stratigraphic distribution, abundance, and diversity of many elements of the fauna such as brachiopods. Ostracods were very abundant and diverse through many parts of the section. Although limited in stratigraphic distribution, the crinoid fauna is the most diverse Palaeozoic fauna collected from Mongolia to date and supports the hypothesis that the CAOB was a biodiversity hotspot in the aftermath of the Frasnian–Famennian extinction event.

A palynological study from Sweden reveals stable terrestrial environments during Late Silurian extreme marine conditions

ABSTRACTA palynological study of the upper Silurian Öved–Ramsåsa Group in Skåne, Sweden yields a well preserved spore assemblage with low relative abundances of marine microfossils. In total, 26 spore taxa represented by 15 genera were identified. The spore assemblage is dominated by long-ranging cryptospore taxa, and the trilete spore Ambitisporites avitus-dilutus. However, key-species identified include Artemopyra radiata, Hispanaediscus lamontii, H. major, H. verrucatus, Scylaspora scripta and Synorisporites cf. libycus. Importantly, Scylaspora klintaensis was identified, allowing correlation with the Klinta 1 drillcore (Skåne). A Ludlow age is inferred for the exposed succession, which agrees well with previous conodont stratigraphy. The organic residue is dominated by phytodebris and spores, but with high relative abundances of acritarchs at two levels, possibly related to flooding surfaces.Based on the palynofacies analysis, a near-shore marine environment is proposed. The close proximity to land is inferred by the high proportions of spores, and the dispersed assemblage most likely represents the local flora growing on delta plains. The palynological signal also infers a stable terrestrial environment and vegetation, in contrast to unstable conditions in the marine environment characterised by ooid formation in an evaporitic environment. Comparisons with coeval spore assemblages from Gotland, Avalonia and Laurentia show relatively close similarities in taxonomic composition at the generic level.