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4 April 2014

Friday fold: ‘Ben Folds One’

Friday fold: ‘Ben Folds One’

We have a guest Friday fold today, from reader Ben Mackay-Scollay of the Monash University School of Geosciences in Melbourne: Ben writes: Hey there Professor Bentley, been a fan of your blog for a while and I thought you might be able to use this for your Friday Fold series. It’s an upright fold at Bermagui in New South Wales, where I visited recently as part of my post-grad coursework …

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6 March 2014

Puzzling over the Wallbridge Unconformity along Corridor H

Puzzling over the Wallbridge Unconformity along Corridor H

The Wallbridge Unconformity is a surface of stratigraphic hiatus or erosion between the depositional influence of the Tippecanoe and Kaskaskia epeiric seas. After Alan Pitts and I located ourselves in the Oriskany Sandstone (terminal Tippecanoe stratum), we looked stratigraphically above the quartz sandstone for the overlying unit, which should be the Needmore Formation shale (beginning of the Kaskaskia sequence). Indeed, the quartz sandstone was overlain by a black shale at …

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5 March 2014

Oriskany Formation quartz arenite and its fossils, Corridor H

Oriskany Formation quartz arenite and its fossils, Corridor H

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 limestones and below the Needmore Shale. We were using Lynn Fichter’s indispensible stratigraphic column for …

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17 February 2014

A marine incursion in the Hampshire Formation?

A marine incursion in the Hampshire Formation?

I went out last Tuesday to Corridor H, the exemplary new highway cutting through the Valley and Ridge province of eastern West Virginia. Joining me was former student Alan Pitts, a devotee of Corridor H from way back in the early days when we just called it “New Route 55.” The boondoggle highway is now open all the way west to the Allegheny Front, practically into the Canaan Valley. On Tuesday, …

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3 February 2014

Ice seeps along Passage Creek

Ice seeps along Passage Creek

This past week, there’s been a beautiful sight along the stretch of the Fort Valley Road that goes past the Blue Hole section of Passage Creek. Click to enlarge Ice has been forming beautiful forms as groundwater seeps out along bedding planes in the Massanutten Sandstone (a Silurian-aged quartz arenite, folded during late Paleozoic Alleghanian deformation). At this site, the bedding dips moderately to the south. This is close to …

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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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1 October 2013

New macro GigaPans of sedimentary rocks from the Massanutten Synclinorium

I have two new GigaPans of hand samples to share with you this morning… The Edinburg Formation graptolites from Mint Spring, Virginia, that I featured here back in May, can now be explored in GIGAmacro hand sample: link Students: are these colonial or solitary organisms? Benthic, nektonic, or planktonic? Does this relate to their usefulness as index fossils? And here’s a graded bed from the Martinsburg Formation (Ordovician turbidites) exposed …

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15 August 2013

Disconformity in northern Colorado

Disconformity in northern Colorado

Have a look at this lovely (almost glowing) example of a disconformity between Coloradan limestone and overlying sandstone.

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25 April 2013

Deformation in the Lake Vermillion Formation

Today, let’s go back to the Pike Dam, where we spent some lovely moments last week, agog at the lovely graded beds and flame structures visible there. In contrast, today we want to examine the deformational structures seen elsewhere at this same outcrop. There are folds and faults and joints and more exotic fare: tension gashes and Riedel shears. The deformation here is the youngest to affect the Vermillion District …

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23 April 2013

Return to the Outdoor Lab

Return to the Outdoor Lab

Two years ago, I took a trip to the Phoebe Hall Knipling Outdoor Lab, which is Arlington, Virginia’s outdoor education facility in the Pond Mountains (southern continuation of the Bull Run Mountains), on the eastern edge of the Blue Ridge geologic province. I was invited back last week to look at some new exposures. I brought the GigaPan along. There had been additional erosion on the saprolitic exposure of Harpers …

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