Abstracts
ABSTRACT
The Siegat Formation (Silurian - early Llandovery) of northwestern New Brunswick represent*. In part, an ancient example of a aubmarlne canyon sequence, erosive Into and partially coeval with the Carye Ml11a Formation of lata Ordovician— middle Llandovery age. The canyon succession contains a moderately diverse ichno-fauna consisting of Buthotraphie, Chondritea, anguineu*, LfipliohniteB, Fuousopeia, Gordia arauata, Gordia, Gyrochorie, Belmintkoida labyrinthioa, tielminthopeia cf. obeli, Seonereitea bieerialie, Neonereitea unieerialie, Planolitee beverleyeneia, Prozopaleodictyon, Scalarituba mieeourieneie and Skolithoe. These trace fossils are described in detail.
Contrary to previous prediction* that dwelling burrows and associated traces would predominate in submarine canyon sequences, the 5iegaa Formation contains traces produced essentially by vaglle 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 lnfaunal sediment feeding organiama.
RESUME
Situee au nord-oueai du Nouveau-Brunawlck, la formation de Siegas (Sllurien — Llandovery inferleur) represents, en partie, un exemple anclen de sequence de canyon eoue-marin; elle recoupe la formation de Carya Mills (Ordovlclen superleur — Llandovery Doyen) et eat en partie contempersine a cette demiere. On rencontre dana la sequence une ichnofaune moderement diverse comprennant Buthotrephie, Chondrites, Cochliahnue , , Pueueopeie, Gordia arauata, Gordia, Gyrochorze, Helrrinthoida labyrinthica, Helmin-thopaie of. obeli, Keonereitee bieerialie, Neonereizee unieerialie, Planolitee beverleyeneia, Protopaleo-dicZyon, Saalaritvba miaaourienaie et Skolithoe. Ces traces foselles eont decrites en detail.
Selon les predictions anterleures, les terriers d'habltation et les traces connexes devralent predomlner dans les sequences de canyon sous-marin mala contralrement i cecl, la formation Siegas contlent plutSt des traces produltea eaaentlellement par des lngesteurs de sediment vagiles- Au mleux, cecl pourralt s'expllquer par l'exclualon d'une population active et abondante d'anlmaux flltreurs, due a 1'absence dans le canyon, au molns la plupsrt du temps, de courants de fond slgnlficatifs. Au lieu de cela, lea sediments devslent con-tenir sufflsamment de detritus organiques pour accomoder une population active d'organlsmes endoblontefi llmnlvores.
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