Abstract

A 4 m thick section in the late Ordovician sequence on Manitoulin Island revealed four successively shallowing carbonate environments, each with a distinctive fossil assemblage. The lowermost quieter water, muddy level bottom community was dominated by the brachiopod Zygospira. Next, increased laminar current action attracted smaller colonies of the tabulate corals Tetradium and Columnopora, and locally small banks of corals and stromatoporoids were built up. In the protected shallow subtidal community following, encrusting algae (Girvanella) and upright match-stick Hedstroemia were more important, alongside Columnopora, cup corals, and a diverse association of thick-shelled bivalves and gastropods. The short-term paleoecological succession terminated under turbulent conditions with large colonies of Labechia, rugose coral colonies of Cyathophylloides, and tabulate corals such as Tetradium forming what is called the Wekwemikong biostrome.

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