structure

Bedding / cleavage relations in the Stephen Formation, Yoho NP

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Good afternoon! Here are a few photos, both plain and annotated, showing the relationship between primary sedimentary bedding and tectonic cleavage in the “tectonised Stephen” Formation atop the Cathedral Escarpment (in Yoho National Park), just northeast of the Walcott Quarry where the (thicker, basinward) Stephen Formation hosts the Burgess Shale. Weathering exploits both these planes … Read more

Friday fold: Three more from the Chancellor Slate

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Remember our examination of buckle folding versus passive folding in the Chancellor Slate (cleaved limy mudrock) of eastern British Columbia? Well, here’s another example: There’s so much awesomeness going on in that image, it’s hard to know where to start. The prominent black thin layers are buckled in a very boxy, asymmetric way. In places, … Read more

Boudinage in Santorini schist

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While on my blueschist quest, I noticed this boudin train exposed in the trail. I’m not sure what exactly is being boudinaged here – only that it is lighter in color than the schist that surrounds it, as well as finer grained and less foliated (more massive). A tabular mass of fault gouge perhaps?