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29 September 2017

Friday folds: soft sediment deformation in thin sections of MTD sandstone

The Friday folds are small soft-sediment deformational features within a dismembered, folded sandstone (a “ploudin”) from a mass transport deposit from the latest Devonian of West Virginia.

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11 August 2017

Friday fold: Eagle Rock

For the Friday fold, Callan digs out images of Eagle Rock, Virginia, well aged in his digital archive for a decade!

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23 May 2017

Silurian tidal flat carbonates of the Tonoloway Formation

Journey to the Silurian period in what is today the Valley & Ridge province of eastern West Virginia to see some exquisite sedimentary rocks that represent deposition in a very arid, very shallow setting.

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9 May 2017

Ripples in Foreknobs

The Foreknobs Formation is a Devonian unit in the Valley & Ridge province of the Mid-Atlantic Region. It was deposited in relatively shallow near-shore conditions during the Acadian Orogeny. On a field trip to Corridor H, a new highway transecting the West Virginian Valley & Ridge province on Monday, I stopped to document a couple of beds showing very nice ripple marks. These ones are symmetrical, and thus likely represent …

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16 May 2016

Trace fossils in the Massanutten Sandstone

Over the weekend, my wife and I took a walk with our son at the Storybrook Trail, an accessible trail with a fine overlook to the east over the Page Valley. There, the Massanutten Sandstone shows a bunch of big beefy trace fossils at this site: both bedding-parallel (Arthophycus-like) and bedding-perpendicular (Skolithos-like) traces. Here’s Bax on a photogenic slab of the quartz arenite, showing the inch-wide bioturbation: A short distance …

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25 October 2015

Cool fossils from the Clearville member of the Mahantango Formation

On Saturday, I took my historical geology class on their field trip out to Corridor H, West Virginia. We made a stop at the Mahantango Formation outcrop exposed on the eastbound exit ramp near Baker, and poked around there for fossils. These Devonian-aged siltstones are chock full of invertebrates including rugose corals, crinoids, articulate brachiopods, and even trilobites. Here are two of the best fossils we encountered there: A trilobite …

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14 August 2015

Paleoslump features and fluvial incision in the Conemaugh Group, West Virginia

The answer to this week’s geological interpretation contest is revealed, sort of. Annotations, GigaPans, and outcrop detail photos reveal the story of equatorial fluvial incision and ancient slumping during the Carboniferous ice ages.

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5 August 2015

Ripple marks and trace fossils in the Rose Hill Formation

An outcrop of Silurian-aged Rose Hill Formation in West Virginia reveals excellent examples of ripple marks and trace fossils.

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30 April 2015

Early Paleozoic fossils in Nealmont Formation, Germany Valley, West Virginia

Looking at Ordovician carbonates in Germany Valley, West Virginia, a few weeks ago on Rick Diecchio’s GMU sedimentology and stratigraphy course field trip: Lots and lots of brachiopods… Crinoid columnals mized with brachiopods: A set of coarsely-infilled trace fossils: Crinoid stem: Nice strophomenid brachiopod: Bryozoan? Receptaculid?

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24 March 2014

Monday migmatite

Here’s a sweet little sample of migmatite (~470 Ma late Ordovician Taconian Orogeny, U/Pb date from zircon), that my students and I spotted last week on the Billy Goat Trail, downstream of Great Falls in Maryland’s metamorphic Piedmont province: Note the white translucent quartz, the orangey (partially kaolinitized and rusty stained) opaque potassium feldspar, and the shreds of biotite torn and tangled between them: I love the fact that I …

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