The Depositional Environment of the Queenston Formation in Southern Ontario

Abstract

<p>The Queenston Formation has been interpreted as a non-marine deltaic deposit since the turn of the century because of its apparent lack of fossils, and evidence for subaerial exposure. The source of the sediment was interpreted to be an orogenic zone in New York or Pennsylvannia.</p> <p>Features such as gypsum nodules and limy siltstones were interpreted as being secondary. However, petrographic studies have found that the siltstones contain marine fossils and some gypsum nodules have inclusions of halite. Moreover, the fine sand grains in the mudrock are not aeolian. Paleocurrents indicate that the source of the sediment transport was generally north-south not east-west. The siltstone and limestone interbeds are flat based, graded, and show no evidence for channeling. Some beds also contain large escape burrows.</p> <p>It is proposed that the Queenston Formation was deposited as a supratidal; mudflat that was regularly flooded by the sea. The mud could have been transported by longshore drift from a river somewhere towards the north, as the paleocurrents in the Queenston mimic major tradewind patterns for the Late Ordovician.</p>