Middlesex/punctata Event in the Rhenish Basin (Padberg section, Sauerland, Germany) – Geochemical clues to the early-middle Frasnian perturbation of global carbon cycle

A positive carbon stable isotope excursion of about 3‰is documented in the topmost lower Frasnian at Padberg, eastern Rhenish Massif, as a muted record of the worldwide early−middle Frasnian isotopic perturbation (punctata Event; up to 6–8‰ shift in both δ13Ccarb and δ13Corg elsewhere), comparable with the Appalachian δ13C curve. This German isotopic signature occurs in a 12 m thick calciturbidite succession and correlates well with the three-step chemostratigraphic pattern known from the Holy Cross Mountains, Poland. It is especially clear in the δ13Corg shifts, whilst δ13Ccarb (and elemental geochemical) proxies are partly biased by post-sedimentary alterations. The New York State, Polish, Nevada and Padberg conodont successions place the onset of the major positive δ13C excursion slightly beneath the early–middle Frasnian boundary, with Ancyrodella nodosa (previously Ad. gigas form 1) as the main conodont guide species, and coincident with the Middlesex transgression and spread of cold, nutrient-rich, poorly oxygenated water masses. In the light of geochemical proxies, enhanced primary production and oxygen deficiency occurred evidently in the Rhenish Basin during the punctata Event. Moderate Hg enrichments in the early Middlesex/punctata Event interval suggest a volcanic signature. However, conclusive data from other regions are required to differentiate between effects of the regionally wellknown synsedimenary magmatism and of a possible global volcanic trigger for the biogeochemical perturbation

The cephalopod-rich Famennian and Tournaisian of the Aguelmous Syncline (southern Maïder)

Highlights - Lower Famennian black shales with (primary) pyritic cheiloceratids and large tree logs. - Middle Famennian goniatite shales at Madène el Mrakib. - Anoxic Lower and Upper Annulata Events. - Upper Famennian rich Platyclymenia faunas. - Hypoxic Dasberg Crisis Interval, followed by rich Gonioclymenia faunas. - Uppermost Famennian Wocklumeria nodules. - Hangenberg Black Shale of Mrakib with unique preservation of goniatite and clymeniid jaws. - Global Hangenberg Crisis Interval with regressive, thick clastic wedges. - Lower Tournaisian goniatite shales with rich Acutimitoceras and Gattendorfia faunas at Tazoult and Bou Tlidat. - The unique topmost lower Tournaisian Kahlacanites fauna at Bou Tlidat. - Global Lower Alum Shale Event followed by basal middle Tournaisian Goniocyclus faunas

New upper Givetian to basal Frasnian conodont faunas from the Tafilalt (Anti-Atlas, Southern Morocco)

Conodont faunas, mostly from previously unsampled sections of the Tafilalt (eastern Anti-Atlas, Morocco) and spanning the upper Givetian to basal Frasnian, include first records of species for the region and NW Gondwana as well as new taxa: "Ozarkodina" maroccanica n. sp., Polygnathus aequidivisus n. sp., Po. dengleri sagitta n. ssp., Po. jorfensis n. sp., Po. saevus n. sp., Po. tafilensis n. sp., and Schmidtognathus longicavus n. sp. The morphology of Tortodus subsymmetricus n. sp. suggests relation ships of Tortodus with Frasnian ancyrognathids. Other taxa are described in open nomenclature: Po. cristatus n. ssp., Icriodus aff. I. symmetricus, Skeletognathus aff. Sk. norrisi, and enigmatic supposed Pb elements (Gen. et sp. indet.). Ctenopolygnathus lanei Kuzmin (1995) is emended and distinctive morphotypes are recognized in Ct. angustidiscus and Po. collieri. Mesotaxis falsiovalis Sandberg et al. (1989) is a subjective junior synonym of the widely over looked M. guanwushanensis (Tian, 1988). There vised regional lithostratigraphy and conodont sequences allow to refine the upper Givetian zonation. The former Upper disparilis Zone is subdivided into succes sive Po. dengleri sagitta and Po. dengleri dengleri subzones. The basalmost Frasnian Ancyrodella rotundiloba pristina Zone (= MN 1 Zone) is preserved as a thin, condensed lime stone just at one locality (Bine Jebilet). The over lying Frasnes Event Beds (Lower Styliolinites) seem to fall in the subsequent Ad. rotundiloba soluta Zone (MN 2 Zone). Records of rare taxa, such as Po. paradecorosus, Po. Pollocki Morphotype 1, old est Po. webbi, Ct. angustidiscus, and Ct. lanei may be help ful for correlation into distant areas or shallower facies

Prospects for an upper Givetian substage

New ammonoid and conodont data from Germany, the Montagne Noire (France) and southeastern Morocco document a complex sequence of sedimentary events and faunal changes within an extended Givetian (late Middle Devonian) Taghanic Event Interval or Taghanic Biocrisis. Direct association of supposed typical middle Givetian ammonoids, trilobites and corals with upper Givetian marker taxa such as pharciceratids have been found, for example, in Moroccan and French time equivalents of the New York Upper Tully Limestone. The initial and eustatic Taghanic Onlap level is not known to be characterized by the first appearance of any widespread index conodont, goniatite or other taxon. A future upper Givetian substage, therefore, might be based either on the entry of Ozarkodina semialternans or on the first appearance of Schmidtognathus hermanni. The semialternans Zone correlates with a third sedimentary cycle within the Tully Limestone and with the spread of the first Pharciceratidae. Eobeloceratidae (Mzerrebites juvenocostatus) and Archoceratidae n. fam. (Atlantoceras). The (Lower) hermanni Zone is marked by a post-event transgression which led to a significant conodont radiation and to a further diversification of Pharciceratidae and Eobeloceratidae (Mz. erraticus). Neue Ammonoideen- und Conodonten-Daten aus Deutschland, Frankreich (Montagne Noire) und aus Südost-Marokko belegen eine komplexe Abfolge sedimentärer Ereignisse und von Faunenwechseln in einem längerfristigen Taghanic-Event-Intervall bzw. einer Taghanic-Biokrise des Givetiums (oberes Mittel-Devon). Direkte Vergesellschaftungen von Ammonoideen, Trilobiten und Korallen, die früher als typische Mittel-Givetium-Formen angesehen wurden, mit Leitformen des Ober-Givetiums (z. B. Pharciceraten) konnten in Marokko und Frankreich in Zeitequivalenten des Oberen Tully-Kalkes von New York nachgewiesen werden. Der initiale und eustatisch bedingte Taghanic Onlap ist bisher nicht durch das Einsetzen eines weit verbreiteten Index-Conodonten, -Goniatiten oder eines Vertreters anderer Fossilgruppen gekennzeichnet. Eine künftige Ober-Givet-Unterstufe sollte daher entweder durch das Einsetzen von Ozarkodina semialternans oder durch das erste Auftreten von Schmidtognathus hermanni definiert werden. Die semialternans-Zone korreliert mit einem dritten Sedimentations-Zyklus im Tully-Kalk und mit der Ausbreitung erster Pharciceratidae, Eobeloceratidae (Mzerrebites juvenocostatus) und Archoceratidae n. fam. (Atlantoceras). Die (Untere) hermanni-Zone ist durch eine Post-Event-Transgression gekennzeichnet, welche eine wichtige Conodonten-Radiation und eine weitere Diversifizierung der Pharciceratidae und Eobeloceratidae (Mz. erraticus) ermöglichte. doi:10.1002/mmng.20010040107</a