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24 June 2022

Friday fold: Kinked Lynchburg metasediments near a soapstone body

Happy Friday! Here are some kink-folded metasediments from Virginia’s Lynchburg Group to help usher in the weekend.

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29 May 2022

Accretionary wedge turbidites from the Lost Coast

The Lost Coast of northern California shows geological evidence of deep sea turbidity current sedimentation, tectonic accretion during Mesozoic subduction, and then isostatic uplift interacting with shoreline erosion. Check out a few photographs taken by Callan’s wife on a recent backpacking trip through the region.

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15 April 2022

Friday fold: Cretaceous Canada

A guest contribution for the Friday fold, from reader Christian Gronau: Christian reports that this is located on the North side of Hwy.11, 20 miles east of Saskatchewan River Crossing, Alberta. Eastern foothills of the Canadian Rocky Mountains. Faulting and folding in Early Cretaceous Luscar Group sediments.  Typical repeating sequence of sandstone, siltstone and coal. Thanks for pitching in, Christian! Happy Friday to all!

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12 November 2021

Friday fold: Raven’s Ridge

Happy Friday, all! Two shots today from my friend Joe up in Vermont. He sends these from the Champlain Valley, at a place called Raven’s Ridge. It looks like an alternating series of sandstones and shales, arched into an anticline, perhaps during the Acadian Orogeny (??). According to the Nature Conservancy’s website, porcupines live in this anticline, which is called “The Oven.” Looks like most of the strata around there …

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25 June 2021

Friday fold: The Blue Ridge Tunnel

Inside the Blue Ridge (in an 1850s-era railroad tunnel), Callan finds folds and boudinage that formed during Appalachian mountain-building.

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11 June 2021

Friday fold: inadvertent kink fold analogue model

It’s Friday! Adam Forte, a geology professor at LSU, posted this image yesterday on Twitter: It’s a box of sheets of newsprint, stored vertically and ignored for a while, now rotated 90° so we’re looking at a cross-sectional view. To me, this is an excellent example of a physical analogue modelling experiment (albeit inadvertent) that demonstrates the process by which kink folds form. The key parameters to get this distinctive …

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7 May 2021

Friday fold: Lynchburg Group

On his way to get his COVID vaccine, Callan visits a new outcrop showing folded and faulted strata of the Neoproterozoic Lynchburg Group.

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16 April 2021

Friday fold: Colorado cluster

Friday means folds –
This week, we head to the Colorado Rockies for a butterfly-like presentation of a ptygmaticly folded granite dike within biotite schist.

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26 March 2021

Friday folds: 3D models by Sara Carena

It’s Friday, and it’s been a few Fridays since I offered you a fold. Let me make up for that with five Friday folds today, all from the incredible collection of free 3D models by Sara Carena on Sketchfab. Sara is a senior scientist/lecturer in Geology at Ludwig-Maximilians University in Munich. Absolutely super models of absolutely super folded rocks. Well done, Sara! Viewing these should get everyone’s weekend off on …

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5 February 2021

Friday fold: a new 3D model

Here’s a good sample, another one I inherited from Declan de Paor when he retired from Old Dominion University. It’s an interesting sample – I guess I’d call it a graphitic clay shale, but it’s surprisingly lightweight, so I’m not super confident that’s right. The bedding surfaces are glossy and slick, indicating some flexural slip between the layers. In terms of composition: It’s too beautiful to cut up and make …

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