Translator Disclaimer
1 July 2010 The Upper Givetian (Middle Devonian) Subterminus Conodont Zone in North America, Europe and North Africa
Katarzyna Narkiewicz, Pierre Bultynck
Author Affiliations +

Late Givetian and early Frasnian conodont communities with Icriodus subterminus have been revised on the basis of collections from Iowa (USA), the Boulonnais and the Ardennes (northern France and Belgium), the Radom-Lublin area and Holy Cross Mountains (Poland), and the Ma'der-Tafilalt region (southeast Morocco). As a result an Icriodus subterminus Zone with a threefold subdivision is defined. The three subzones correspond approximately to the “Lower and Upper subterminus Fauna” and the “insita Fauna” commonly used in N America for the study of shallow-water platform carbonate successions.

The base of the subterminus Zone corresponds to a level within the uppermost part of the hermanni Zone; the top is characterized by the occurrence of the earliest Ancyrodella taxa, Montagne Noire Zones MN 1 and the base of MN 2 or slightly above the base of the falsiovalis Zone.

The diagnosis of Icriodus subterminus is amended and two morphotypes are recognized. The stratigraphic range of the alpha morphotype is confined to an interval between the uppermost part of the hermanni Zone and the top of the MN 3 Zone; the beta morphotype may range into the MN 6 Zone.

The holotype of Icriodus subterminus from the North Liberty beds in Iowa is most likely a specimen that was reworked from the Cedar Valley Limestone. Icriodus cedarensis and Icriodus tafilaltensis are described as new species, and the diagnoses of Icriodus excavatus and Icriodus expansus are amended. Between the Icriodus difficilis and Icriodus symmetricus zones, an Icriodus expansus Zone is defined.

Katarzyna Narkiewicz and Pierre Bultynck "The Upper Givetian (Middle Devonian) Subterminus Conodont Zone in North America, Europe and North Africa," Journal of Paleontology 84(4), 588-625, (1 July 2010).
Accepted: 1 March 2010; Published: 1 July 2010

NW Gondwana
subterminus Zone
Get copyright permission
Back to Top