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You are browsing the archive for 2014 October.

31 October 2014

Friday fold: Four folds from VGFC

Here are four folds from the Potomac Terrane (or maybe an “exotic unit” that looks like the Potomac Terrane, butted up against the Potomac Terrane) that I saw on the 2014 Virginia Geological Field Conference back in October. It was an overcast, rainy day, so I apologize for the relatively low quality of these images. Happy Friday!

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30 October 2014

Geomystery: what are these white lines?

Esteemed readership, I’ve got a mystery for you. What are these white lines, inclined consistently at a high angle to bedding? I picked up this sample below the “Wall of Death,” on the trail from Wapta Lake below Mount Wapta, en route to the Walcott Quarry of the Burgess Shale. The “zebra-striped” rock is of the Eldon Formation of the Cambrian section in Yoho National Park. At first, I thought …

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29 October 2014

A beefy stylolite

I saw this large, chunky stylolite this summer somewhere along the trail from Takkakaw Falls to the Walcott Quarry of the Burgess Shale (in Yoho National Park, British Columbia). I like the way weathering has highlighted its form.

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28 October 2014

Glacial striations

Today, I thought I would share some images of lovely “textbook” glacial striations from rocks I saw in the Canadian Rockies this summer…

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27 October 2014

Yamnuska

Driving west from Calgary, your first evidence of entering the Canadian Rockies’ Front Ranges is the startling sheer cliff of Yamnuska, north of the Trans-Canada Highway: Yamnuska’s shape is a function of differential weathering of the two rock units that make up the mountain: Cambrian Eldon Formation limestone, and Cretaceous shales of the Brazeau Formation. The Cambrian is the uppermost of the two, which is a violation of superposition, considering …

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26 October 2014

Bedding / cleavage relations in the Stephen Formation, Yoho NP

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 of weakness… Here, the cleavage is more planar at the bottom of the sample, and …

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25 October 2014

GSA and the Biggs Award

The recently-concluded Geological Society of America meeting in Vancouver, British Columbia, was one of my best meetings ever. I gave two talks and a digital poster, supervised three student digital posters and one student group regular poster, attended and contributed to meetings on a variety of subjects, met new colleagues, reunited with old friends, and even attended some stimulating science talks. Plans were hatched, ideas refined, projects discussed. Tuesday was …

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24 October 2014

Friday fold: Three more from the Chancellor Slate

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, the layer is discontinuous, suggesting faulting or shortening via pressure solution. Note how the cleavage …

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17 October 2014

Friday fold: Santorini schist

Happy Friday! Here’s some folded schistocity in the schist of Santorini’s Cycladean subduction complex: The blunt crest of the fold in the second photo appears to be a folded marble boudin. Neato!

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16 October 2014

Boudinage in Santorini schist

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?

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