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18 November 2015

Beach sand of coastal Maine

You could use a macro GigaPan of some pretty sand, I think. Link That’s sand from near Acadia National Park, in Maine. Exploring it, you can find both small chunks of Acadian granite, and green rods that are sea urchin spines. It’s fun – check it out.

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29 September 2014

Charnockite at Swift Run Gap

Over the weekend, I ran a 1-credit field course for NOVA, on the geology of Shenandoah National Park. I was about eight minutes early getting to the meet-up location, so that allowed me to check out a promising new outcrop of rock along the road (route 33, ~100 m west of Swift Run Gap). Here are two photos of it: charnockite (pyroxene-bearing granitoid or meta-granitoid), with weak foliation: This is …

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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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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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26 March 2014

The Great Unconformity in the Franklin Mountains

Good morning! Let’s take a walk up the east side of the Franklin Mountains, north of El Paso, Texas, to walk across the Great Unconformity. The basement rock exposed here is the Red Bluff Granite, a 1.1 Ga felsic magma that intruded the columnar basalts of the Mundy “Breccia” and the Castner Marble. (It is unknown what substrate the Castner Marble was deposited upon.) This is what the Red Bluff …

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24 October 2013

Exploring Wind River Canyon’s Great Unconformity in outcrop and hand sample (via GigaPan)

Over the summer, I shot these two GigaPans of the “Great Unconformity” in Wind River Canyon (Owl Creek Mountains), Wyoming: link link This week, Team M.A.G.I.C. (by which I mean my student Robin Rohrback-Schiavone) finished up a series of three macro GigaPans of rock samples from the site (made with our one-of-nine-in-the-world GIGAmacro rig by Four Chambers Studio): link link link In combination, these five images could be used to …

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4 September 2013

Granite balls, boudins, and tadpoles in Archean schist, Laramie Range, Wyoming

A final post from my visit to the Laramie Range with Bob Bauer and Fred McLaughlin earlier in the summer -Recall that there is schist and granite at this site, and much of the granite shows cross-cutting or inclusive relationships indicating it is younger than the schist, while still younger mafic dikes cross-cut than the granite. Both exhibited folding. However, in other places, we observed the opposite: granite inclusions within …

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1 July 2013

Which is older?

Using your relative dating prowess to determine which of these two rock units is older, the schist (dark gray) or the granite (light pink): Click to enlarge Click to enlarge Justify your answer by citing a principle of relative dating.

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