23 December 2014

More oncoids (from the Peyto Formation?)

Posted by Callan Bentley

Two years ago, I posted on some interesting structures my students and I saw at Consolation Lakes, near Moraine Lake in Banff National Park. They were little concretions, “oncoids” roughly speaking, and may have indicated (thanks Howard!) that the boulders were sourced to the Peyto Formation, a Cambrian carbonate within the Gog group:

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The purpose of today’s post is to confirm that these structures are still there two years later, and to post a few more photos of them:

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Note the negative weathering the oncoids show relative to the surrounding matrix.

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I also found a couple of boulders at a new location, in the lateral moraine of the Athabasca Glacier that had the same features, though less oxidized…

Boulder #1:

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Boulder #2:

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Note the ooids (upper right) and radial cracks in the “oncoid” here:

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