Invertebrate ichnology of the nonmarine Lepreau Formation (Triassic), southern New Brunswick, eastern Canada

Abstract

Alluvial fan and braided fluvial redbeds of the Triassic Lepreau Formation of southern New Brunswick, eastern Canada, contain a moderately diverse and abundant invertebrate ichnofauna. Fourteen formal ichnotaxa are recognized: Ancorichnus coronus, Ancorichnus cf. A. ancorichnus, Aulichnites isp., Cruziana problematica, Fuersichnus isp., Gordia marina, Palaeophycus striatus, Palaeophycus isp., Planolites isp., Rusophycus isp., Skolithos linearis, cf. Skolithos isp., and Taenidium isp. Two vernacular ichnotaxa, “inclined meniscate burrows” and “surface pit structures,” also occur. All these ichnotaxa are figured and briefly described. Collectively, the entire assemblage can confidently be assigned to the Scoyenia ichnofacies that, in the Lepreau Formation, represents a fluvial channel ichnocoenose.

Specimens have been subject to marked taphonomic effects due to weathering and preservation in lithologies showing either insufficient variation in grain size or a grain size too coarse to preserve subtle morphological variations; as a consequence, ichno-taxobases are commonly obscured or obliterated. This may have influenced the apparent diversity of the assemblage, especially with regard to meniscate and simple horizontal burrows. It is proposed that application of “taphoseries,” theoretical series including ichnotaxa that may potentially be mistaken for each other with increasing taphonomic overprint, provides a safeguard against ichnotaxonomic misidentifications.