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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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21 June 2022

Another example of overturned bedding

One of my favorite tricks is using bedding / cleavage intersections to identify tectonically inverted strata. On a field trip yesterday to check out soapstone quarries in the Albemarle/Nelson border region, I got to see this lovely example of Lynchburg Group metasediments that showcased a textbook example of the phenomenon: Bedding was initially horizontal, or close to it, and cleavage (formed under tectonic compression) initially vertical. Subsequent deformation rotated the …

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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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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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12 July 2019

Friday fold: Wiltondale, Newfoundland

Here is an outcrop of folded limestone along route 430 in Newfoundland, inside Gros Morne National Park, just west of the crossroads called Wiltondale: A detailed look at the left antiformal portion of the outcrop: A zoomed-in examination of the rightmost part, where a goopy looking synform resides: Just down the way, a second outcrop shows another fold with the same sense of asymmetry, on a smaller scale: Happy Friday …

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11 July 2019

A submarine slump complex at Sandy Cove, Newfoundland

Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.

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14 June 2019

Friday fold: kinked cleavage at Harpers Ferry

Last weekend was the annual meeting of the eastern section of the National Association of Geoscience Teachers. On Friday afternoon, we visited Harpers Ferry, West Virginia, and my colleague Beth Doyle led a great field trip to examine the rocks exposed there. This was my favorite outcrop we saw: Here is a close up of this outcrop, which is framed by (anthropogenic) rock wall: Dipping shallowly from upper left to …

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18 March 2019

New discoveries in the Martinsburg Formation

A virtual field trip to examine some deepwater clastic sediments shed off the first phase of Appalachian mountain building, and deformed in the third phase. It’s a lovely day for a field trip to the late Ordovician!

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8 February 2019

Friday fold: Falte an der Riedbergpaßstraße im Allgäu

A Friday fold from Germany showing an overturned sequence of sedimentary layers. Bedding / cleavage relationships show which limb is tectonically inverted. Furthermore, this fold was an “Aha!” moment for the budding geological mind of a small boy.

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22 August 2018

Q&A, episode 5

A reader asks: “What is foliation and what makes it so important to the structure of rock?”
Callan answers with a lot of images of beautifully foliated rocks.

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15 July 2018

Chickie’s Rock, Pennsylvania

A virtual field trip to the deformed quartzites and metaconglomerates of Chickie’s Rock and Sam Lewis State Park in Lancaster County, Pennsylvania.

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13 July 2018

Friday fold: the anticline at Chickie’s Rock

Chickie’s Rock is a prominent cliff of Cambrian quartz arenite (sandstone) in Lancaster County, Pennsylvania. I visited it last month with field trippers at the eastern section meeting of the National Association of Geoscience Teachers. One of the aspects of the site is this gentle anticline with axial planar cleavage: The yellow rectangle is my field notebook for scale. Another shot: Happy Friday to all!

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13 February 2018

S-C fabric in limestone, Camerino, Italy

Some scaly Italian limestone shows off two foliations (S and C) which reveal the kinematic motions that built the Apennines.

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21 July 2017

Friday fold: Sardinia

My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking: Ander says: The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and grain size variation do an excellent job highlighting compositional layering. They were deformed during the …

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27 March 2017

Cleaved, boudinaged, folded Edinburg Formation southwest of Lexington

Explore a dozen photos highlighting the structural geology of an outcrop of limestone and shale near Lexington, Virginia. Cleavage refraction, overturned beds, boudinage, folds, and even a small fossil – we’ve got something for everyone. Bring the whole family!

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6 June 2016

Cleavage refraction in Konnarock Fm. rhythmites – a virtual sample

Here’s a visualization combination that leverages the advantages of the GIGAmacro system with the 3D ‘virtual sample’ perspective of the Sketchfab-hosted model: the same sample presented in both formats. In this case, it’s a lovely example of cleavage refraction going from meta-clay-shale (now ‘slate’) through a graded bed of fine sand and silt. [gigapan id=”187755″] Link GIGAmacro by Callan Bentley [sketchfab id=”fb3eb77f46524d15b3a23649c63cd863″ start=”0″ spin=”” controls=”0″] Photoscan model by Marissa Dudek …

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22 April 2016

Friday fold: Crumpled Dinwoody Formation, Sheep Mountain, Wyoming

Today for your folding pleasure, I give you two field GigaPans shot by Jeffrey Rollins, a two-time Rockies field course alumnus and Old Dominion University student working under my colleague Declan De Paor, assisted by NOVA student Bridget Gomez, during last summer’s extended GigaPan expedition at the Sheep Mountain Anticline, Wyoming. This particular outcrop was found near the axis of the massive Laramide fold, and shows an extensively deformed section …

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19 November 2015

A little geologic history before breakfast

What geological stories can be read from the stone on the front of a building? Walking past some facing stone in Baltimore, Callan discovers a wealth of little clues.

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12 October 2015

Bedding/cleavage GigaPans at Harpers Ferry, WV

I’ve been thinking lately about Harpers Ferry, the spot where West Virginia, Virginia, and Maryland meet, at the confluence of the Potomac River and the Shenandoah River. I’ve noted small outcrops of its overturned beddding here previously, and also described a book I read about the man who made the place infamous: John Brown. I went out there again last week with my NOVA colleague Beth Doyle, and we explored …

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9 October 2015

Friday fold: Apennine crenulation cleavage

My new social media buddy Samuele Jæger Papeschi and I collaborated on some goofy maps in August, but then he noticed my Friday folds, and like the very best human beings anywhere, Samuele offered to pitch in with a few folds of his own. (Other readers are encouraged to do the same!) Today, I’ll feature the first of them – though others will follow in weeks to come. That is crenulation cleavage …

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