Trace fossils in a Lower Palaeozoic submarine canyon sequence — the Siegas Formation of northwestern New Brunswick, Canada
DOI:
https://doi.org/10.4138/1374Abstract
The Siegas Formation (Silurian - early Liandovery) of northwestern New Brunswick represents. In part, an ancient example of a submarlne canyon sequence, erosive into and partially coeval with the Carye Mills Formation of latae Ordovician— middle Liandovery age. The canyon succession contains a moderately diverse ichno-fauna consisting of Buthotraphie, Chondrites, Choclichnus anguineus, Diplichnites, Fuousopsis, Gordia arauata, Gordia, Gyrochorte, Helminthoida labyrinthioa, Helminthopsis cf. abeli, Neonereites biserialis, Neonereites uniserialis, Planolites beverleyensis, Prozopaleodictyon, Scalarituba missouriensis and Skolithos. These trace fossils are described in detail. Contrary to previous predictions that dwelling burrows and associated traces would predominate in submarine canyon sequences, the 5iegaa Formation contains traces produced essentially by vagile sediment eaters. This ia perhaps bear explained by the absence within the canyon, at least for the majority of time, of sufficiently strong bottom currents, which precluded inhabitation by an active and abundant suspension feeding population- Instead, the sediments probably contained sufficiently abundant organic detritus to support an active population of infernal sediment feeding organisms. RÉSUMÉ Située au nord-ouest du Nouveau-Brunswick, la formation de Siegas (Silurien — Liandovery inférleur) représents, en partie, un exemple ancien de séquence de canyon sous-marin; elle recoupe la formation de Carya Mills (Ordovlclen supérieur — Liandovery Doyen) et est en partie contemporaine à cette dernière. On rencontre dans la séquence une ichnofaune modérément diverse comprennant Buthotraphie, Chondrites, Choclichnus anguineus, Diplichnites, Fuousopsis, Gordia arauata, Gordia, Gyrochorte, Helminthoida labyrinthioa, Helminthopsis cf. abeli, Neonereites biserialis, Neonereites uniserialis, Planolites beverleyensis, Prozopaleodictyon, Scalarituba missouriensis et Skolithos. Ces traces foselles sont décrites en détail. Selon les prédictions antérieures, les terriers d'habltation et les traces connexes devraient prédominer dans les séquences de canyon sous-marin mais contrairement à ceci, la formation Siegas contient plutôt des traces produited essentiellement par des ingesteurs de sédiment vagiles- Au mieux, ceci pourrait s'expliquer par l'exclualon d'une population active et abondante d'animaux filtreurs, due à l’absence dans le canyon, au moins la plupart du temps, de courants de fond significatifs. Au lieu de cela, les sédiments devsient con-tenir suffisamment de détritus organiques pour accomoder une population active d'organismes endobioutes limnivores. [Traduit par le journal]Downloads
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