Abstract

An Ordovician flysch trace fossil assemblage from the Aroostook–Matapedia Carbonate Belt, northern New Brunswick, consists of the following identifiable ichnogenera: Alcyonidiopsis, Asteriacites, Asterosoma, Belorhaphe, Bifasciculus, Buthotrephis, Chondrites, Cochlichnus, Cosmorhaphe, Diplichnites, Fucusopsis, Glockeria, Gyrochorte, Helminthoida, Helminthopsis, Neonereites, Paleodictyon, Planolites, Protopaleodictyon, Scalarituba, Spirodesmos, Spirorhaphe, and Taenidium. The stratigraphic range of six ichnogenera, viz. Glockeria, Gyrochorte, Helminthoida, Spirodesmos, Spirorhaphe, and Taenidium, is, therefore, now extended to rocks of Ordovician age.The diversity exhibited by the assemblage is inconsistent with currently proposed models of Phanerozoic flysch trace fossil diversity. It is suggested that existing models suffer from an inadequacy of sampling and systematic effort per period of geological time, as reflected by the limited number of post-Cambrian/pre-Cretaceous, particularly post-Carboniferous/pre-Cretaceous, adequately documented flysch ichnoassemblages. The assemblage described here clearly illustrates a significant radiation of deep-sea behavioural diversity in the Ordovician. This is possibly related to the development during the Ordovician of a sufficient oxygen concentration and supply of organic detritus in the deep sea or colonization of deeper-water habitats concomitant with the significant diversification of Ordovician shelf benthic communities.

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