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8 December 2015

Considering the Spechty Kopf diamictite

I have known for a long time about a diamictite in the latest Devonian part of the Appalachian stratigraphic sequence, since it is exposed in the lowermost part of the section (western end of the outcrop) at Sideling Hill, Maryland. When I led field trips there, I talked students through the multiple possible origins for diamictites (sedimentary rocks that are poorly sorted, with significantly “outsized” clasts “floating” in a finer-grained …

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1 December 2015

Which way’s up? Check cavity fills.

When snail shells are deposited in a bunch of sediment, they serve as tiny architectural elements, with a “roof” that protects their interiors. Any sediment mixed into the shell’s interior will settle out (more or less horizontally), and then there will be empty space (filled with water, probably) above that. As burial proceeds and diagenesis begins, that pore space may be filled with a mineral deposit, such as sparry calcite. …

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30 November 2015

Slump in progress on Corridor H

I was out on Corridor H last week, looking at rocks with my Honors student, and on the way back from the field work, I noticed this: Click to enlarge That’s a fresh slump scarp running across a slope that is gradually sliding downhill. (The left half of the image is moving down relative to the right.) To judge from the rip-rap-filled culverts, this slope must have a previously-documented history …

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27 October 2015

Corridor H virtual field experience

My Historical Geology class was in for a new experience for the semester’s capstone field trip. Before we headed out into the field (to the exceptional roadcuts along Corridor H in Grant and Hardy Counties, West Virginia), we had them examine all the outcrops virtually, in the comfort of the classroom, using digital imagery. I say “we” because this initiative was a collaboration with my colleague Alan Pitts, who developed …

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26 October 2015

Tool marks, trace fossils, and flute casts from the Brallier Formation

Another gem from Saturday’s Historical Geology field trip: the bottom of a fine sandstone bed in the Devonian Brallier Formation, showing a variety of primary sedimentary structures, including tool marks, trace fossils, and several flute casts. Current flow direction here would have been from upper left toward lower right. Here’s a version of the photo with a few of these features highlighted:

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25 October 2015

Cool fossils from the Clearville member of the Mahantango Formation

On Saturday, I took my historical geology class on their field trip out to Corridor H, West Virginia. We made a stop at the Mahantango Formation outcrop exposed on the eastbound exit ramp near Baker, and poked around there for fossils. These Devonian-aged siltstones are chock full of invertebrates including rugose corals, crinoids, articulate brachiopods, and even trilobites. Here are two of the best fossils we encountered there: A trilobite …

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12 October 2015

Bedding/cleavage GigaPans at Harpers Ferry, WV

I’ve been thinking lately about Harpers Ferry, the spot where West Virginia, Virginia, and Maryland meet, at the confluence of the Potomac River and the Shenandoah River. I’ve noted small outcrops of its overturned beddding here previously, and also described a book I read about the man who made the place infamous: John Brown. I went out there again last week with my NOVA colleague Beth Doyle, and we explored …

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5 October 2015

Trace fossils in the Juniata and Tuscarora Formations

Route 33 in Pendleton County, West Virginia cuts across the lower Paleozoic stratigraphic section. I went there this past spring on a sedimentology and stratigraphy field trip with the GMU sed/strat class. The trip was orchestrated by professor Rick Diecchio. Here are some scenes from two of the stops – the upper Ordovician Juniata formation (red sandstones and shale intepreted as Taconian molasse) and the overlying Silurian Tuscarora Formation (thick …

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14 August 2015

Paleoslump features and fluvial incision in the Conemaugh Group, West Virginia

The answer to this week’s geological interpretation contest is revealed, sort of. Annotations, GigaPans, and outcrop detail photos reveal the story of equatorial fluvial incision and ancient slumping during the Carboniferous ice ages.

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28 July 2015

Millboro Formation shale in outcrop and in hand sample

Another site from the GMU sedimentology field trip in April: An outcrop on Route 33 in Brandywine, West Virginia, showing the Millboro Formation. It’s mostly shale, with some intriguing sandstones, too. There are fossils and diagenetic carbonate nodules (concretions). Here’s the outcrop, the largest GigaPan I’ve taken so far (7.9 billion pixels): [gigapan id=”171447″] link The shale itself looks… like shale. It’s fine-grained, and dark (high carbon content, suggesting low …

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13 November 2014

Gypsum casts? You be the judge — UPDATE: Syneresis cracks!

Silurian aged mud cracks feature small lensoidal features: are they casts of ancient gypsum crystals?

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10 October 2014

Friday folds: ploudin trio from Corridor H

Three folded sandstone slab-blobs will serve as today’s Friday folds. Meet the ploudins!

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2 July 2014

Fault breccia in the Helderberg Group, Corridor H

Here’s a breccia that Dan Doctor and I found in a tabular zone within the Helderberg Group (Devonian limestones) in one of the massive new roadcuts along Corridor H. [gigapan id=”157860″] link Is it a fault breccia or a sedimentary breccia? The breccia was bedding parallel, which suggests it could be just another bed, but it’s so darn coarse and angular (unlike the rest of the Helderberg) that we were …

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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? [gigapan id=”103090″] link [gigapan id=”142740″] link This time, however, my eye was drawn to the prodigious quantities of mudcracks to be seen in side-view (that is, …

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20 February 2014

Stylolite from the Helderberg Group, exposed on Corridor H

While out on the Corridor H field trip last week before the heavy snow, I found this squeal-inducingly-lovely example of a stylolite in Helderberg Group limestones (Devonian passive margin carbonates): The stylolite is a pressure-solution surface, made especially apparent in this example because of the starkly different grain sizes and colors on either side of the dissolved-away rock: This is a gorgeous sample to explore in macro GigaPan view. Enjoy: …

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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. [gigapan id=”142740″]┬álink This GigaPan turned out well in some regards, and …

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22 December 2011

Virtual sample gigapan #1: pyrolusite dendrites on limestone

With my new “macrogigapan” rig from Four Chambers Studio, I produced this image last week before I left on vacation: [gigapan id=”94714″] That sample measures 18.5 cm long, and is about 4.9 cm wide. Pretty good resolution, eh?

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4 November 2011

Friday fold: Anticline / syncline pair

Today’s fold is an anticline and its neighboring syncline, both exposed along a newly-opened stretch of New Route 55, west of Moorefield, West Virginia. The new Route 55 is a classic porkbarrel boondoggle courtesy of the late Senator Robert Byrd, but doggone if it didn’t open up some lovely new roadcuts. Here’s a stitched image of the fold, with my student Jared at center right for scale: You can click …

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