Dresbachian trilobites and stratigraphy of the Cass Fjord Formation, western North Greenland

Abstract

Twenty-five species of trilobites are described, some in open nomenclature. They represent four faunules of Dresbachian age and one faunule of possibie pre-Dresbachian age from the lower 150 m of the Cass Fjord Formation in Daugaard-Jensen Land, western North Greenland. The Cass Fjord Formation ranges in age from Middle Cambrian-Early Ordovician, although until recently it was widely assumed to be entirely of Ordovician age. All the trilobites are typical North American endemic forms. New taxa include: Bonneterrina greenlandica n. sp., Prolonchocephalus spinosus n. gen. n. sp., Kingstonia peltate n.sp., and Terranovella arcuata n. sp. Biogeographic affinities of the older faunules are with faunas of the inner part of the carbonate belt of the Cordilleran region, while the younger faunules have affinities with faunas from the outer(?) part of the carbonate belt in the northern Appalachian region. Evidence of extension of the Dresbachian-Franconian cratonic unconformity to western North Greenland is presented and the problem of repetition of trilobites in the crisis fauna at the base of the Pterocephaliid biomere is discussed.