6 June 2014

Friday fold: differential weathering of carbonate intraclasts in mudstone

Posted by Callan Bentley

Howard Allen is the documentarian of this week’s fold:


Howard writes that this is:

Middle Cambrian Chancellor Formation rock with recessive weathering intraclasts(?). Hamilton Lake trail, Yoho National Park, British Columbia. My interpretation of this one is a little shaky–it was raining when I took the photo (in 1982) and I was hiking with a non-geologist friend, so I didn’t linger at the outcrop or record the precise location. I think this is a mudstone, probably siliceous, with carbonate intraclasts, or something similar (perhaps chunks of algal mat?); the whole thing has a rather supratidal look about it. The surface is roughly normal to bedding (a joint surface, I think), and the rock is clearly folded, as can be seen in the acute angle to the lower left of the lens cap. I’d like to get a better look at this in the future. Location is west of Emerald Lake, approximately 51.440, -116.555.