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1 May 2015

Friday fold: Tight syncline/anticline pair in Brallier Formation

The Friday fold shows clastic detritus (turbidites or “flysch” from the Acadian Orogeny) crumpled into tight folds due to the later Alleghanian Orogeny.

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6 April 2015

Exploring Mahantango Zoophycos traces in GigaPan

Recently, I posted about an excellent road cut in Fort Valley showing well-developed 10 cm+ Zoophycos trace fossils. Presented here are three new GigaPan images (two outcrop; one macro) of Zoophycos from the Devonian-aged Mahantango Formation: link link link These images are part of a new “virtual field trip” that I organized to supplement my historical geology field trip to examine the geologic history of the Massanutten Synclinorium. The link …

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24 March 2015

Martinsburg Formation outcrops in Edinburg Gap

A report from the field: new outcrops of Ordovician-aged turbidites featuring geopetal indicators, fossil content, and a structural overprint imparted during Pangaea’s assembly.

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20 March 2015

Friday fold: flexed turbidites

Spring is almost here! As you get ready for the equinox, enjoy this gentle fold on a Friday: These are turbidites (graywacke and shale) of the late Ordovician Martinsburg Formation, seen in Edinburg Gap, western Massanutten Range, greater Shenandoah Valley, Virginia. Bedding is flexed very slightly here, from moderately-dipping to more steep, and then back to moderate again. Slickensides on the top of some exposed layers indicate the beds shifted …

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19 March 2015

Zoophycos trace fossils in Mahantango Formation, Fort Valley

A morning’s field trip yields an outcrop of excellent Zoophycos trace fossils in southern Fort Valley, Virginia.

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26 December 2014

Friday fold: another gem from the Chancellor Slate

That pretty much speaks for itself, I reckon.

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12 December 2014

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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27 October 2014

Yamnuska

Driving west from Calgary, your first evidence of entering the Canadian Rockies’ Front Ranges is the startling sheer cliff of Yamnuska, north of the Trans-Canada Highway: Yamnuska’s shape is a function of differential weathering of the two rock units that make up the mountain: Cambrian Eldon Formation limestone, and Cretaceous shales of the Brazeau Formation. The Cambrian is the uppermost of the two, which is a violation of superposition, considering …

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8 August 2014

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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9 May 2014

Friday fold: knuckling under in the Mesilla Valley shale

Here’s a fold I saw in Texas, in the Mesilla Valley shale, close to the contact with the Muleros Andesite at Cristo Rey: This is a pretty wild looking fold. Let’s zoom in on the most deformed portion: Annotation: white is top of the distinctive, blocky, buckled bed, and black is its bottom side. Red shows brittle fractures in that same bed: Looks as if it rolled over on itself …

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