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24 October 2014

Friday fold: Three more from the Chancellor Slate

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

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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10 October 2014

Friday folds: ploudin trio from Corridor H

Friday folds: ploudin trio from Corridor H

Three folded sandstone slab-blobs will serve as today’s Friday folds. Meet the ploudins!

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3 October 2014

Friday fold: En route to Santorini over the Cyclades

Friday fold: En route to Santorini over the Cyclades

A glimpse out an airplane window reveals some Cycladean geology in the Aegean Sea. Somewhere down there among the metamorphic rocks is our Friday fold… but nary a volcano in sight.

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26 September 2014

Friday fold: passively folded marble

Friday fold: passively folded marble

It’s Friday! Here’s Baxter, last Friday, in Athens, Greece. He’s checking out some folds in the marble that’s everywhere in that city: This is a lovely example of passive folding, where all the rock layers being folded have about the same viscosity (low viscosity contrast between layers). No buckling, as a result… Enjoy the weekend, hopefully passively!

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19 September 2014

Friday fold: Miette Group anticline in Banff National Park, Alberta

Friday fold: Miette Group anticline in Banff National Park, Alberta

Here’s an outcrop of Miette Group slate, seen at the intersection of the Icefields Parkway with the Trans-Canada Highway, just north of Lake Louise, Alberta: There’s a lovely anticline just to the right of Zack, who obligingly provided a sense of scale. Also note how cleavage which is subparallel to bedding on the far left side of the outcrop, becomes perpendicular to bedding along the crest of the anticline… Happy …

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12 September 2014

Friday fold: Quartz vein in Catoctin Formation, Point of Rocks, Maryland

Friday fold: Quartz vein in Catoctin Formation, Point of Rocks, Maryland

I took this image in 2005, when I was working up a geologic history of the C&O Canal National Historical Park. It’s a vein of quartz, gracefully folded within the Catoctin Formation. The exposure is along the railroad tracks at Point of Rocks, Maryland, easternmost extent of the Blue Ridge province on the north shore of the Potomac River. The Culpeper Basin begins about 100 meters to the east of …

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5 September 2014

Friday fold: Kink banding in the Arran Islands

Friday fold: Kink banding in the Arran Islands

This one is in my folder of ‘structure’ images on my computer, but it’s not one of mine. I’m not sure where it came from. A TinEye search turns up nothing. Perhaps one of  you can tell me? Lovely subparallel kink bands… such gorgeous structure. Happy Friday!

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29 August 2014

Friday fold: Pleistocene glacial folding of Cretaceous sedimentary rock?

Friday fold: Pleistocene glacial folding of Cretaceous sedimentary rock?

The Friday fold is found in Cretaceous rocks of eastern Alberta – but far beyond the tectonic influence of the Canadian Rockies. So what’s responsible for the folding?

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8 August 2014

Friday fold: Buckle vs. passive folding in the Chancellor Group slates

Friday fold: Buckle vs. passive folding in the Chancellor Group slates

The Friday fold is an outcrop in Yoho National Park that showcases differences between buckle folding and passive folding.

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