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19 December 2014

Friday Fold: Mist Mountain Formation in Canmore, Alberta

Friday Fold: Mist Mountain Formation in Canmore, Alberta

Let’s journey to the Cretaceous today, to see sandstones, shales, and even some coal strata that have been folded during the eastward thrusting that built the Canadian Rockies. Here’s the same fold, in context, shot in GigaPan on a different day, from a different angle. Can you match it up? link Ben Gadd showed me (and my field class) this site last summer. It’s a little west of Canmore. There’s …

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12 December 2014

Friday fold: Miette slate, Alberta

Friday fold: Miette slate, Alberta

The Friday fold returns to Canada, looking at Neoproterozoic slate and quartzite at the southern terminus of the Icefields Parkway. Bonus features include ripple marks, graded beds, cross-bedding, cleavage, and boudinage.

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5 December 2014

Friday folds from the Shenandoah River

Friday folds from the Shenandoah River

My student Josh B. found this beautiful map view of a plunging fold in the bed of the Shenandoah River, as viewed in Google Earth: Josh posted his results on Facebook, and then the other Josh (Joshua Villalobos of El Paso Community College) poked around the area and found some others downstream (north): Here’s a Google Maps link to the site. Check it out!  

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14 November 2014

Friday fold: GSW fall field trip

Friday fold: GSW fall field trip

Last Saturday was the Geological Society of Washington’s fall field trip. Dan Doctor, Alan Pitts, and I led a team of ~20 geologists out to the great new exposures along Corridor H in West Virginia. Here’s the team in front of some of the parasitic anticlines and synclines that decorate the larger structure of the Patterson Creek Mountain Anticline: The strata here are Silurian-aged tidal flat carbonates of the Tonoloway …

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31 October 2014

Friday fold: Four folds from VGFC

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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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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