Good morning! Let’s take a walk up the east side of the Franklin Mountains, north of El Paso, Texas, to walk across the Great Unconformity. The basement rock exposed here is the Red Bluff Granite, a 1.1 Ga felsic magma that intruded the columnar basalts of the Mundy “Breccia” and the Castner Marble. (It is … Read more
Where the Needmore Formation is falling apart on Corridor H, sloughed-off shale is piling up in a tiny talus slope: You could slap a protractor on that photo and get a pretty good measurement of the angle of repose of this chippy, flaky granular material. Eyeballing it, that looks like about 45° to me.
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 … Read more
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 … Read more
A photo of the iconic dune cross-beds at Zion National Park gets the Bentley Annotation treatment, and comes out looking like a stained glass window. Take a look at both photos and see if you can answer the question, “Which way was the wind blowing?”
Another guest Friday fold – again, from the structural geologist Christie Rowe at McGill University in Montreal: Christie describes this as: growth faulting in beautiful fluvial sediments… Accordingly, I have squinted and annotated it a bit: Happy Friday!
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, my friend and colleague Pete Berquist snapped this image of a stretched pebble conglomerate in the structure teaching lab: Some nice examples of pressure solution evidence in there … Read more
I think this one of the most fascinating batches of sand we’ve yet had the pleasure of macro-GigaPanning: link So much igneous goodness hidden in those grains, collected from a beach on the south of Iceland… The image was made by Robin Rohrback-Schiavone (my student at NOVA) as part of the Mid-Atlantic Geo-Image Collection (M.A.G.I.C.). … Read more
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 … Read more
Lily and I took our son to the Virginia Scottish Games on Sunday. This is an annual competition of events in traditionally Scottish feats – throwing heavy things, mainly. There is also fried food, whisky, and some terrific music. The event is held at the Great Meadow, south of The Plains, Virginia. I had never … Read more
A lovely example of a volcanic breccia (from the Eocene Absaroka Volcanics of southern Montana) is showcased, in two different photographs.
A week ago, I featured six new GigaPans here, of the extraordinary rocks in Klingle Valley, DC. I hadn’t been able to get the next phase of imaging that site ready in time for the post, but here it is: an annotated view of the outcrop. Annotation color code: PINK = Granite contact BLUE = … Read more
Last week, I mentioned some geologizing with the family in the Staunton area. The furthest west we ventured was to the road connecting Deerfield, Virginia, with West Augusta. There, the Brallier Formation is well exposed in a dramatic roadcut. Explore it for yourself in this M.A.G.I.C. GigaPan: link The Brallier is turbidites, shed off the … Read more
Following on yesterday’s post about the kink bands within the strained metagraywacke of the Laurel Formation in DC, let’s take the opportunity today to go to Klingle Valley, site of a different facies within the Laurel Formation: a strained metaconglomerate. Though the exposure isn’t as great as the Purgatory Conglomerate, I think you’ll find plenty … Read more
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 … Read more
Callan and his colleague Jay Kaufman (University of Maryland) go to extraordinary lengths to document an intriguing block of rock in northern Virginia’s Blue Ridge province. Great images and a lot of fun result – but what do these rocks tell us?
Callan showcases some extraordinary depositional structures (graded bedding and flame structures) seen in Archean turbidites in the Superior province of northern Minnesota.
Yesterday I drove down I-81, through the heart of Harrisonburg, Virginia, and the campus of James Madison University. On the east side of the road, a big new slump / earthflow caught my eye. On my way back up the same stretch of road today, I pulled over and photographed it: Panorama 1 (click to … Read more
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
The Friday fold photo was taken this morning on a GigaPanning expedition, and shows a small syncline within turbidite strata of the Martinsburg Formation, Page Valley, Virginia.