ALBERT

Description: The Givetian pelagic and dysoxic outer shelf facies of the Dra Valley (SW Morocco) yielded as minor benthic faunal elements a number of stringocephalid and uncitid brachiopods that allow a precise correlation of these marker brachiopods with the regional, detailed goniatite zonation. In a reverse situation, the predominant neritic shallow-water succession of the Bergisch Gladbach area (Rhenish Massif, Germany), which is characterized by a detailed succession of stringocephalids and Uncites, has yielded rare and new Middle Givetian goniatite species. These findings allow, with some help of conodont data, neriticpelagic correlations within and between widely separated basins. New species are Tornoceras n. sp. from the Buchel Formation (with coloration remains), Trevoneites' paffrathensis n. sp. from the Lower Plattenkalk Formation, and Maenioceras heinorum n. sp. from the Hornstein Member. New material of stringocephalids and Uncites is described from the Dra Valley. The identical, well-defined range of Uncites (U.) gryphus gryphus in the lower to middle parts of the Middle Givetian of the Dra Valley and Rhenish Massif underscores the stratigraphical significance of this genus that was widely distributed in Europe, northern Gondwana, the Urals, and Central and Eastern Asia.

Description: During the Global Taghanic Biocrisis ( c. 385 Ma), Middle Devonian faunas worldwide underwent extinction. In the biocrisis type region, the northern Appalachian Basin, biodiversity changes occurred through three bioevents that ultimately resulted in the loss of numerous endemic taxa. Carbon isotope excursions during this biocrisis have been documented in various stratigraphic successions, but never in the type region. Herein, we reconstruct changes in 13 C carb from the biocrisis type region and compare these changes to local faunal transitions. An approximately 1.5 negative excursion corresponds to the first bioevent, a time of inferred global warming and replacement of most endemic taxa of the mid-palaeolatitude Appalachian Basin by invasive palaeoequatorial taxa. An approximately 2 positive excursion is associated with the second bioevent, recognized as a return of the endemic fauna and the loss of invasive taxa. This positive excursion occurs near the Polygnathus ansatus–Ozarkodina semialternans zonal boundary and is recognized elsewhere. Faunal cosmopolitanism associated with the third bioevent corresponds with an inflection in the carbon isotope record from negative to positive trending values, which agrees with a positive carbon record excursion seen elsewhere at the semialternans – Schmidtognathus hermanni zonal boundary. This new carbon isotope record provides an important reference for recognizing this biocrisis in other areas and facies. Supplementary material: The 13 C and 18 O dataset collected for this study is available at http://www.geolsoc.org.uk/SUP18840 .

Description: 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