valley and ridge

Nice plume

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Another scene from the South Page Valley Martinsburg outcrop featured here last week: a slightly mud-bedecked example of plumose structure. This plume occurs within a single graded bed (turbidite) of the Martinsburg Formation. It gets younger (paleo-up) to the right. The joint propagation that the plumose structure records began somewhere vertically above the area of … Read more

Mystery fossil (?) for crowd-sourced identification

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A Fort Valley neighbor brought me this sample yesterday, asking me to tell her what it was. But while my brain’s pattern-recognition centers lit up when examining its “rows” of scale-like bumps, it didn’t match up with anything that I know from anywhere else here. Take a look, and click any of these images to … Read more

GigaPan suite from the South Page Valley Martinsburg Outcrop

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Are you into structure? Sedimentology? Stratigraphy? Well, I’ve got some good news for you – I’ve imaged several key outcrops on the newly-discovered (to me) roadcut on South Page Valley Road, showcasing the middle Martinsburg Formation turbidites (and their Alleghanian structural overprint). link link link link link link See if you can find: an anticline … Read more

Incipient boudinage in overturned Edinburg Formation

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Boudinage is such a fun structure. Here’s an example from the roadcut adjacent to the quarry featured so heavily last week. The thick limestone stratum in the center of the photo has been stretched left-to-right. It exhibits pinch-and-swell structure, the first stage of boudinage. Small extensional fractures began to form in the boudin necks, accommodating … Read more

Friday fold: the case of the strangely stout stylolites

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Today, we return to my field trip from last week, for a look at an odd outcrop of the Ordovician-aged Edinburg Formation: Note the car key with green lanyard, to provide a sense of scale. It’s folded, as the yellow bedding traces show in this annotated version: But what really caught my eye about this … Read more

Upper Martinsburg “Cub Sandstone” in GigaPan

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Today, two GigaPans shot of the uppermost Martinsburg Formation, informally known as the “Cub Sandstone” since it crops out along Cub Run in the southern part of the Massanutten range. 10 or 15 meters upsection (west) of these two outcrops is the base of the Silurian-aged Massanutten Sandstone, the ridge-forming unit. Lower in the section: … Read more

A closer look at the recumbent anticline from last Friday

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Last week, the Friday fold was presented in GigaPan format only, which led to a concerned reader lamenting that he couldn’t see it on his mobile device. (GigaPans are Flash-based images; they don’t work on Apple devices in the standard GigaPan format, though there is a perfectly suitable workaround with two extra clicks.) So, for … Read more

Bouma ABE

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The initials ABE might make you think of Lincoln, but that’s not what I’m talking about. Today, the letters mean something else: three subdivisions of the 5-part Bouma sequence of turbidites. I took these photos on a new (to me) outcrop of the Ordovician-aged Martinsburg Formation in Page County, Virginia. I visited the site for … Read more

Friday fold: a recumbent anticline in an abandoned quarry

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Yesterday, I spent a pleasant day in the field with John Singleton, the new structural geology professor at George Mason University. I was showing John a couple of sites I’ve used as field trip locations for the GMU structural geology class, and John was showing a couple of new sites to me – places he … Read more

Using M.A.G.I.C. to zoom in on trace fossils

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Yesterday, I worked on my sabbatical project, the Mid-Atlantic Geo-Image Collection (M.A.G.I.C.). Whether I go outside on a given day to shoot GigaPans of local geology depends on multiple factors: (a) How’s the weather? (b) Do I have to watch Baxter? (c) Can I bring Baxter with me? (d) How are the lighting conditions? Yesterday … Read more

Strained stylolites in Elkton East

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Whoa – look at all that GREEN. You can tell this Virginia picture wasn’t taken recently. In fact, it’s another image from the field review I participated in for the Elkton East quadrangle back in May of last year. Somehow I start blogging these things, but run out of steam (or really more accurately: I … Read more

Friday fold: Up on Opequon Creek

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I got a call last month from Rebekah Wiedower, a landowner up in Frederick & Clarke counties (her family’s property includes pieces of both), inviting me to come up and look at some anticlines and synclines that Dan Doctor (USGS) had identified on the bank of Opequon Creek. I was glad to do it, though … Read more

Living in the Appalachian Forest, by Chris Bolgiano

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Last week, I finished reading Living in the Appalachian Forest: True Tales of Sustainable Forestry, by Chris Bolgiano. It’s a grab-bag of stories from the forested mountains of the south-central Appalachians, ranging from Pennsylvania down to Kentucky and maybe Georgia, too. West Virginia and Virginia get the most attention. The driving question behind the book … Read more