valley and ridge

Rugose corals in the Clearville member of the Mahantango Formation

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Here are some rugose coral fossils (along with some cross-sectioned articulate brachiopod shells) to be seen in the Clearville member (~80 feet thick) of the Mahantango Formation, exposed on the north side of route 55, just west of the West Virginia / Virginia border. These fossils are cool in their own right (what fossils aren’t?) … Read more

Friday fold: Contorted Rome Formation next to the Max Meadows Fault

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My student Mercer Parker shot this one over to me the other day: Click to enlarge Those are the slim strata of the Rome Formation (a.k.a. Shady*), strongly deformed in the region adjacent to the Max Meadows (“M&M”?) Fault. Thanks, Mercer! _____________________________________________ * Will the real slim Shady please stand up?

Fault breccia in the Helderberg Group, Corridor H

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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. 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 … Read more

Palimpsest tales from a Silurian limestone

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My favorite rocks are those that tell multiple stories – rocks that are “palimpsest” with subsequent “chapters” of their biography capable of being teased out, based on different features to be observed in the rock. Click to enlarge What can we see in this small sample of the Silurian-aged Tonoloway limestone, from Corridor H, West … Read more

Faults in the Tonoloway Formation, Corridor H

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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 … Read more

A new diamictite exposure (Devonian?) along Corridor H

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While on Corridor H last week with Team “Border to Beltway” (and USGS research geologist Dan Doctor), we stopped at the putative mass transport deposit. We still haven’t figured out which unit this is (It’s not the Foreknobs), but as we approached it, Dan wondered aloud, “I wonder where the top of the Devonian is. … Read more

Friday fold: Paw Paw Tunnel anticline

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As with last week, the Friday fold comes from my Field Studies in Geology class to Sideling Hill and the Paw Paw Tunnel. This is a view of the downstream (north) entrance to the Tunnel, with students highlighting the trace of bedding in the turbidites of the Brallier Formation: Can’t make it all out? Let’s … Read more

Friday fold: Sideling Hill

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Here’s what the Sideling Hill road cut looked like last month: It’s a terrific example of a syncline. Usually I show folds in profile view, but here, the view is essentially perpendicular (not parallel) to the axis of the fold: Sideling Hill’s rocks are early Mississippian in age, made of debris shed off the late … Read more

Bloomsburg Formation exposed near Elizabeth Furnace

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As noted previously, I live in a regional scale fold: the differential erosion of the Massanutten Synclinorium has produced the ridge of Massanutten Mountain, which separates the Fort Valley from the Shenandoah and Page valleys on either side. The Fort is “fort” like because the strata which underlie it are relatively friable, soluble, or otherwise … Read more

Oriskany Formation quartz arenite and its fossils, Corridor H

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Today, a few more photos from the field trip last month to Corridor H, the fine new superhighway with so little traffic out in eastern West Virginia. Our antepenultimate stop of the day was at an outcrop we inferred should hold the Oriskany Sandstone, a Devonian quartz arenite that lies stratigraphically above the Helderberg Group … Read more

Friday fold: limestones of the Silurian, Corridor H

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For the Friday fold, let’s journey back to the Silurian, as exposed in the limestones of that age that were deformed during Alleghanian mountain-building (Pennsylvanian and Permian), and exposed along Corridor H in eastern West Virginia. Some buckling (cuspate-lobate form) seen in that one… A little pop-up with hinge collapse: And, finally, as a digestif, … Read more

A fistful of fossils (Devonian Helderberg Group of West Virginia)

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More images for you today from my field trip a few weeks ago to West Virginia’s bizarro highway Corridor H, a quiet place built for roaring traffic. Its multistory roadcuts are fresh and profound; they offer the most incredible views into the mid-to-late-Paleozoic surface of Earth… and the creatures that lived there. In the Devonian … Read more

Carbonate mudcracks in cross-section (Tonoloway Formation)

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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? link link This time, however, my eye was drawn to the … Read more

Halite casts (hoppers) from the Wills Creek / Tonoloway Formations in West Virginia

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While we’re out on Corridor H, let me show you some new halite casts I found (either the Wills Creek Formation or the Tonoloway Formation): Salt casts are among my favorite primary structures. They speak very specifically to hypersaline depositional conditions.

Stylolite from the Helderberg Group, exposed on Corridor H

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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 … Read more