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You are browsing the archive for June 2014 - Mountain Beltway.

27 June 2014

Friday folds: Acadian metamorphics and pegmatite from coastal Maine

Some folds this week from coastal exposures in western Boothbay Harbor, Maine, where I’m on vacation for one more day… Acadian metamorphics (schist, gneiss), with injected granite pegmatite that has also been folded (and boudinaged): Happy Friday!

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26 June 2014

The eyes have it

Okay, I photoshopped that one up. This one too… Here are the originals… And, if you’re a scale-off-to-the-side-of-your-main-subject purist, here’s a different shot of this quintessential boudin: And, while we’re at it, here are some other fine boudins (of granite pegmatite) exposed along the coast of West Boothbay Harbor, Maine: Some nice coastal ecology to be seen in that last shot, eh?

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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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20 June 2014

Friday fold: the Castile Formation at the State line outcrop

The Friday fold visits the Permian basin of west Texas. There, the Castile Formation exhibits gorgeous inter- and intra-bed folding.

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19 June 2014

A preview of tomorrow’s post

That’s the State Line outcrop south of the Guadalupe Mountains, along the Texas / New Mexico border. Know what you can find there? Tune in tomorrow to find out…

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17 June 2014

Weathering on Old Rag Mountain 2: Opferkessel

Yesterday, I pointed out an example of differential weathering on Old Rag Mountain, in Shenandoah National Park, in Virginia. Today, I’d like to shine the spotlight on another example of weathering to be seen along the trail there: little weathering pits that occur on the top of the granite outcrops. These are opferkessel. Some people call these “potholes,” a term I do not approve of in this context. To me, …

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16 June 2014

Weathering on Old Rag Mountain 1: feeder dikes

Old Rag Mountain is a distinctive mountain in the eastern Blue Ridge of Virginia, contained in a little lobe of Shenandoah National Park. It’s a great hike on several levels: (1) it’s got no trees on the summit, so you can actually get a decent view from on top, (2) it’s got a great section of full-body rock scrambling on the Ridge Trail, and (3)  it’s long (9.2 miles round …

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13 June 2014

Friday fold: tortured turbidites at Devil’s Slide

Marek Cichanski (of De Anza College near the south end of San Francisco Bay) contributed this week’s Friday fold: Marek says: The locality is a place near San Francisco called Devils Slide. It is a piece of the coastal highway built along a steep mountainside above the ocean. This unstable stretch of road was recently (finally!) replaced by some tunnels. And, amazingly, the old roadbed finally got converted to a …

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12 June 2014

Slickensides in the Vulcan Quarry, Manassas, Virginia

While at the Vulcan Quarry in Manassas, Virginia, a few weeks ago, the principle interesting feature I saw on the individual blocks of rock we sorted through was slickensides. I saw dozens and dozens of examples, in both the hornfels and the diabase, but here are five nice examples to share: No sense of scale on this last one, because I didn’t feel safe edging up to the quarry wall …

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10 June 2014

Diabase intrusion at the Vulcan Manassas quarry

When I was flying back from Phase I of “Border to Beltway” in Texas this past March, I was delighted to photograph a bunch of local geology from the air, including this prominent diabase quarry in Manassas: I had never been to this particular quarry before, but as it turned out, it was one of our final destinations on Border to Beltway’s second phase, last month. Here’s a closer view …

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