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9 November 2014

Silurian mudcracks in cross-section

Spotted these cross-sectioned mudcracks yesterday on Corridor H, on the GSW fall field trip: They are in the Tonoloway Formation, a batch of tidal flat carbonates with lots of evidence of shallow arid conditions.

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6 October 2014

Non-bedding-parallel stylolites in Tonoloway limestones, Corridor H

What can a little squiggle in a rock tell us? Stylolites in West Virginian limestone cut across the bedding plane, implying Alleghanian tectonic stresses.

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25 June 2014

Pemaquid Point, Maine

Pemaquid Point, Maine, is a locally-owned and -managed park near an old lighthouse. I went there yesterday with my family. We’re on vacation in coastal Maine for a week. At Pemaquid Point, the action of waves have cleaned the rocks, and they offer a delightful three-dimensional look at Acadian-aged metamorphics and granite pegmatite dikes, with a fair amount of structural geology superimposed on the whole lot. Learn more about the …

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5 June 2014

Palimpsest tales from a Silurian limestone

My favorite rocks are those that tell multiple stories – rocks that are “palimpsest” with subsequent “chapters” of their biography capable of being teased out, based on different features to be observed in the rock. Click to enlarge What can we see in this small sample of the Silurian-aged Tonoloway limestone, from Corridor H, West Virginia? To start with, it’s sedimentary, and stratified. There are multiple layers of fine-grained gray …

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4 June 2014

Faults in the Tonoloway Formation, Corridor H

Here’s something fun: Click to enlarge Those strata are Silurian-aged Tonoloway Formation carbonates. There are plenty of dessication cracks to be seen, as well as salt casts, among the layers exposed. But more eye-catching at this distance is the faulting that disrupts the high-contrast layers… Both (apparent) normal and reverse faults can be seen in this road cut. Exciting stuff! We visited it two weeks ago on “Border to Beltway’s” …

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25 February 2014

Carbonate mudcracks in cross-section (Tonoloway Formation)

While on Corridor H 2 weeks ago with Alan Pitts, we stopped astride the Patterson Creek Mountain Anticline, with extensive road cuts displaying Tonoloway Formation overlying Wills Creek Formation. We love this spot for its lovely folds and halite casts. See what I mean? link link This time, however, my eye was drawn to the prodigious quantities of mudcracks to be seen in side-view (that is, in cross-section). Take a …

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24 February 2014

Halite casts (hoppers) from the Wills Creek / Tonoloway Formations in West Virginia

While we’re out on Corridor H, let me show you some new halite casts I found (either the Wills Creek Formation or the Tonoloway Formation): Salt casts are among my favorite primary structures. They speak very specifically to hypersaline depositional conditions.

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3 February 2014

Ice seeps along Passage Creek

This past week, there’s been a beautiful sight along the stretch of the Fort Valley Road that goes past the Blue Hole section of Passage Creek. Click to enlarge Ice has been forming beautiful forms as groundwater seeps out along bedding planes in the Massanutten Sandstone (a Silurian-aged quartz arenite, folded during late Paleozoic Alleghanian deformation). At this site, the bedding dips moderately to the south. This is close to …

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1 November 2013

Massanutten trip double-feature

As soon as I got back from GSA, I had to run two field trips, back to back. Both are the same trip: my Historical Geology field trip to the Massanutten Synclinorium. Here’s yesterday’s crew perched on a moderately-dipping slab of Massanutten Sandstone along Passage Creek: Today, it’s the same routine all over again, though the weather ain’t as purty… Here’s Friday’s group at one of the four Veach Gap …

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19 October 2013

Halite casts from Tonoloway Formation under the GIGAmacro lens

The work of team M.A.G.I.C. continues. This is a lovely sample quartet of salt cast samples from Silurian-aged Tonoloway Formation limestone. I collected these samples on Corridor H’s newly-opened section west of Moorefield, West Virginia, last spring. The big one at the bottom was collected by my friend Leigh Henry, who graciously loaned it to M.A.G.I.C. for imaging purposes. ┬álink This GigaPan turned out well in some regards, and poorly …

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