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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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17 July 2020

Friday fold: Sandy Hollow from the air

The Friday fold is spied below, in the Montanan landscape near Dillon, from an airplane high above…

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6 March 2020

Friday fold: an Extreme(adura) geological history question

The Friday folds are revealed in an elegant cross-section through fantastic rocks in the Extremadura region of Spain.

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28 February 2020

Friday fold: sandbox

The Friday fold is a lovely little sandbox analogue model by Prof. Marco Martins-Ferreira, who posted it on Twitter this week:  As deformation proceeds, you can see the layers develop folds that then morph into faults, shoving deeper layers atop more shallow strata. As a bonus, you can hear Marco’s baby cooing in the background! Here’s a stabilized, sped-up version, courtesy of Anna Williams:  Happy Friday, all!

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18 October 2019

Friday folds from the Foreknobs Formation

TGIF! That’s my seven year old field assistant showing off the shape of a syncline in shale, siltstone, and fine sandstone of the Foreknobs Formation, a Devonian nearshore package of clastic sediment in the Valley & Ridge Province of eastern West Virginia. Want to see something freaky for Halloween? Photoshop can make it happen: Ewwww. Creepy! Another shot of the same fold, with a thick massive sand above a thicker …

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6 September 2019

Friday fold: Gonzen, Switzerland

Science writer Gabe Popkin shared two fold photos with me this week – both from near Sargans, Switzerland, adjacent to the Rhine River Valley and the border with Lichtenstein. The photos shows the mountain called Gonzen. There, Jurassic limestones crop out in a very wavy pattern: I don’t know the geology of this area in any kind of detail, but I decided to trace out a distinctive upper surface of …

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27 July 2019

Offset limestone layers at Broom Point

Yesterday, I featured some folds from Broom Point, but there are also faults there. With the intriguing local limestone conglomerates providing easily-discernible marker beds, these apparently vertical faults are easy to spot. Here are three examples:

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26 April 2019

Friday fold: Black Sands Beach

The Friday fold can be found in a boulder of gray chert layers on Black Sands Beach, at Marin Headlands in California.

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14 February 2019

Friday fold: an arch of gypsum in Sicily

Ahh, Sicily on a Friday morning. Join us to examine a spectacular arch of gypsum from the Messinian evaporite package.

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