Résumés
Abstract
Previous recordings of Late Ordovician-Early Silurian flysch trace fossils (13 ichnogenera, 15 ichnospecies) from slope deposits of the Matapedia Basin at a single site on the Tobique River, western New Brunswick, are supplemented by the addition of 9 newly discovered ichnogenera (12 ichnospecies). These are:- drculichnis montanus, Cruziana problematica, Cruziana cf. stromnessa, Dipt'tchnites ichnosp., Megagrapton irregulare, Monocraterion ichnosp., Phycosiphon incertum, Rusophycus didymus, Rusophycus ichnosp. types A and H,Scolicia ichnosp, and Tuberculichnus ichnosp. The traces are poorly preserved and occur only in low numbers compared to previously documented forms. Nevertheless, the meticulous sampling procedures adopted at the site emphasize the need for detailed collecting, before drawing conclusions regarding diversity models, stratigraphic distribution, etc., of trace fossils. Of these new forms only Diplichnites ichnosp. has previously been recorded from die Matapedia Basin in the partially coeval Lower Silurian Siegas Formation. Tuberculichnus ichnosp. is recorded for the first time in North America. The combined total of 22 ichnogenera (27 ichnospecies) from the Tobique River represents the most diverse ichnocoenosis yet reported from a single ancient slope deposit. The occurrence of several more typically shallow-water ichnogenera (e.g., Cruziana, Diplichnites, Monocraterion and Rusophycus) suggests that, at least in the Early Palaeozoic, caution must be exercised in their utilization as distinctive facies or environmental indicators.
RESUME
9nouveauxichnogenres(12ichnoespeces)s'ajoutentaceuxdejarepertories (13 ichnogenrcs, 15ichnoespcces)enunsite unique localise sur la riviere Tobique, dans 1 'ouest du Nouveau-Brunswick, dans des sediments tardiordoviciens e eosiluriens accumul£s sur le talus continental du Bassin de Matapedia. Ce sont: Circulichnis montanus, Cruziana problematica, Cruziana cf. stromnessa, Diplichnites ichnosp., Megagrapton irregulare, Monocraterion ichnosp., Phycosiphon incertum, Rusophycus didymus, Rusophycus ichnospp, types AetB, Scolicia ichnosp. et Tuberculichnus ichnosp. Cesdemieres sont malconservdes et relativement rares par rapport aux formes deja connues. Ndanmoins, le d£pouillement m&iculeux utilise a ce site d£montre la necessited'unecollecte detailiee avantdetirer des conclusions quant auxmodelesdediversite, aladistributionstratigraphiquc, etc., des traces fossiles. De ces nouvelles formes, seule Diplichinites ichnosp. est deja cormue dans le Bassin de Matapedia, soil dans la Formation sihirienne infeiieure et en partie synchrone de Siegas. On recense Tuberculichnus ichnosp. pour la premiere fois en Amerique du Nord. Le total combine de 22 ichnogenres (27 ichnoespeces) presents sur la riviere Tobique represente l*icrirK>coenoselaplu$divasejamai$repertorieedansunseuldep6tdetalus. Lapresencedcplusieursichnogenrestypiquesd'une faible tranche d'eau (e.g., Cruziana, Diplichnites, Monocraterion et Rusophycus) demontre que la prudence est de misc lors de leur utilisation a litre d'indkateurs de facies on de milieu, tout particulieTement a l'Eopaieozoique.
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