Sedimentology of an Early Silurian carbonate ramp: the Manitoulin Formation, southern Ontario

Abstract

The Manitoulin Formation is a pervasively dolomitized Lower Silurian carbonate unit that was deposited in the Michigan Basin and locally in the Appalachian Basin. The formation reaches a maximum thickness of 11.1 m in southern Ontario and can be subdivided into eight facies and four regionally correlatable facies assemblages. Owing to the relatively continuous transition of shallow to deeper water facies from the northern to southern portions of the study area, the Manitoulin Formation is interpreted as having formed on a carbonate ramp with a southerly component of dip. Our study suggests that the Algonquin Arch, which is transected by the outcrop belt, did not significantly influence deposition or separate the Michigan and Appalachian basins.Depending on its location on the ramp, the Manitoulin Formation shows evidence of varying degrees of episodic storm events alternating with fair-weather processes such as wave shoaling, sediment reworking, and bioturbation. Apart from bioturbation, these fair-weather processes became less prevalent to the south. The gently dipping antecedent topography, the temporary lack of frame-builders, and a shallow basin setting led to the creation of a carbonate ramp rather than a rimmed shelf.La Formation de Manitoulin est une unite de carbonates profondement dolomitisbe, appartenant Silurien infbrieur, qui fut dCposbe dans le bassin de Michigan et localement dans le bassin des Appalaches. L'Cpaisseur maximale de la formation de 11,l m fut atteinte dans le sud de l'ontario, oG la formation est subdiviske en huit faciks dont quatre assemblages faciologiques, peuvent &tre regionalement mis en correlation. Vu la transition relativement continue, du nord vers le sud, des facibs de faible tranche d'eau i eau profonde dans la rCgion etudiCe, la Formation de Manitoulin est interprCt6e comme Ctant form6 sur une rampe de carbonates avec pendage vers le sud. Notre ktude suggbre que l'arc Algonquin, lequel est coup6 transversalement par la zone d'affleurements, n'a pas influencC significativement la ~Cdimentation ou sCparC le bassin de Michigan du bassin des Appalches.Selon l'endroit sur la rampe, la Formation de Manitoulin exhibe, B divers degrb, des indices d'kvknements de tem$tes Cpisodiques alternant avec des processus de temps calme tels les effets des vagues sur haut-fond, le remaniement des sediments et la bioturbation. Hormis la bioturbation, ces processus de temps calme etaient devenus moins actifs au sud. La topographie antecuente de faible pendage, l'absence temporaire d'organismes constructeurs, et le contexte d'un bassin peu profond ont favoris6 le dCveloppement d'une rampe de carbonates plut6t qu'une plate-forme frangee.[Traduit par la rkdaction]Can.

The Late Ordovician Dawson Point Formation (Timiskaming outlier, Ontario): key to a new regional synthesis of Richmondian–Hirnantian carbonate and siliciclastic magnafacies across the central Canadian craton

“…This coloured limestone-dolostone facies association appears to be similar to that found locally in the Lower Silurian Manitoulin Formation of southern Ontario (Anastas and Coniglio 1993). Likewise, red to green siltstones, fine-to medium-grained sandstones, evaporite, and dolomudstones that overlie this succession in the LT-1 core (Fig.…”

Seismites within Ordovician–Silurian carbonates and clastics of Southern Ontario, Canada and implications for intraplate seismicity

“…The northernmost study area extends over~130 km 2 of the central Bruce Peninsula underlain by Ordovician siliciclastic strata that are unconformably overlain by Lower to mid-Silurian dolostones and shales (Sanford et al, 1985;Anastas and Coniglio, 1993;Armstrong, 1993;Armstrong and Carter, 2010). The uppermost exposed strata of the central Bruce Peninsula are mid-Silurian Guelph Formation dolostones (Armstrong, 1993;Armstrong et al, 2002;Coniglio et al, 2003).…”