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You are browsing the archive for culpeper basin.

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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4 December 2013

The Smithsonian Castle and the Seneca Quarry, by Garrett Peck

The Smithsonian Castle is one of the most striking buildings on the National Mall in Washington, DC. One reason for this is its distinctive architecture, but a second reason is its color: a bright, deep red. This color comes from the rock from which the Castle constructed: the Triassic-aged “Seneca Sandstone,” a part of the formation technically known as the Manassas Sandstone. It is overlain by the Balls Bluff Siltstone, …

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12 March 2013

Five new GigaPans from Thoroughfare Gap

Yesterday, I took five new GigaPans at Thoroughfare Gap, a water gap where Broad Run cuts through Bull Run Mountain, the eastern limb of the Blue Ridge Anticlinorium at my latitude. The rocks here are the Cambrian-aged Chilhowee Group, with bedding tilted moderately to the east during Alleghanian mountain-building in the late Paleozoic. To the west is the crystalline core of this massive regional fold, and to the east is …

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18 June 2012

My new commute

Callan describes the geology along his new commute from the Fort Valley east to the Annandale campus of NOVA. The driving route traverses the Valley & Ridge, Blue Ridge, and Piedmont provinces, including the Culpeper Basin, and stops just shy of the Coastal Plain.

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15 May 2012

Diabase dike in diabase

Seen in rip-rap on the side of Naked Creek, a week ago yesterday: This boulder is exotic to its current location. It is typical of medium- and coarser-grained diabase from the Culpeper Basin, a Triassic rift valley east of the Blue Ridge. The main minerals are plagioclase (light-colored) and pyroxene (dark colored).

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8 February 2012

“Got migmatite?”

Had this brainstorm a few weeks back (or maybe months?). Been meaning to blog it up, but hadn’t gotten the chance to flesh it out. The geologic map of the Commonwealth comes from Chuck Bailey of William & Mary, who gave me permission to use it for this project. Anyhow – do you think there are enough Virginia geology nerds out there that I could sell these bumper stickers at …

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27 May 2011

Friday fold(s): the Outdoor Lab

Today’s Friday fold takes me back 25 years, to when I visited the Outdoor Lab with my science class in Arlington County Public Schools. I revisited this exemplary outdoor education facility on Tuesday, at the invitation of its director, Neil Heinekamp. Neil wanted a geology “expert” to take a look at their rocks, and I wanted a chance to check out their rocks as part of my expanding examination of …

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22 May 2011

New hallway display: geologic provinces of northern Virginia

Callan shows off a new hallway display in his building at Northern Virginia Community College, showcasing the numerous geologic provinces of northern Virginia (as well as adjacent mid-Atlantic states).

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26 February 2011

Waterfall Formation outcrops

I first mentioned the Waterfall Formation on this blog in May of 2008, but this was my first time visiting it in situ. Previously, including the May 2008 visit, was memorable time with charismatic boulders of float. The occasion to see this geologic unit in outcrop was the field trip 6 days ago with the George Mason University GeoClub, when we took a hike to Thoroughfare Gap. After looking at …

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