Today, I share with you eight images that I took yesterday on Skyline Drive in Shenandoah National Park: Blocks of Antietam Formation quartzite (meta-quartz sandstone) of Cambrian age, used in the low rock walls of an overlook parking pull-out. They all bear lovely Skolithos trace fossils (seen end-on, and in cross-section):
After my talk Wednesday night to the Potomac Appalachian Trail Club, I got an email from PATC member Tom Johnson, with an extraordinary photo attached. It shows an exceptional outcrop of the Neoproterozoic Catoctin Formation, exposed atop Compton Peak in northern Shenandoah National Park, Virginia. The outcrop features enormous, well-preserved cooling columns from these ancient … Read more
By local prodigy Hannah Holland, elementary school student: Click through to make it bigger and see some details. Nice work, Hannah! Very impressive, and thanks for sharing!
Reader Jacob Langseth sent in this image of a lovely fold that he recently saw in the Blue Ridge province of Georgia. It’s located in an old CCC rock quarry, off of the Pine Log Creek Trail system, in Bartow County. You can click on that first image to make it bigger and see a … Read more
Another thing I saw last week in the Rockfish Conglomerate were several nice examples of “bookshelfing,” which is when a rock or mineral fractures into pieces, and the pieces slide down relative to their neighbors, like a set of encyclopedias slumping outward on a bookshelf. This has the effect of shortening the grain/clast in one … Read more
Callan presents a gazillion photos from a field trip to examine the Rockfish Conglomerate, a potential Snowball Earth glacial outwash facies from the Neoproterozoic of the Virginia Blue Ridge province.
The current edition of the Accretionary Wedge geology blog carnival (hosted by Evelyn Mervine of Georneys) is built around the theme of favorite geology words. My favorite geology word is derived from the French boudin, for sausage. It’s “boudinage,” and it’s best said with a heavy French accent and a leering, dirty expression. “Boo-din-ahhdj” I … Read more
This Friday, I give you a fold from the shores of the Rockfish River, south of Charlottesville, in Virginia’s Blue Ridge basement complex, and just down the road from the Lawhorne Mill High Strain Zone. The fold distorts (and improves) a felsic dike cutting the darker granite of the basement. You can make this (stitched … Read more
Callan attends a field trip in the Blue Ridge of Virginia, looking first at a Paleozoic shear zone that disrupts (and improves) Mesoproterozoic basement complex rocks.
Today’s Friday fold takes me back 25 years, to when I visited the Outdoor Lab with my science class in Arlington County Public Schools. I revisited this exemplary outdoor education facility on Tuesday, at the invitation of its director, Neil Heinekamp. Neil wanted a geology “expert” to take a look at their rocks, and I … Read more
Callan shows off a new hallway display in his building at Northern Virginia Community College, showcasing the numerous geologic provinces of northern Virginia (as well as adjacent mid-Atlantic states).
Last week, the Friday fold featured a kinked phyllite of unknown provenance that is currently resident in David King Hall 2074 on the campus of George Mason University. However, on Tuesday of last week, I found another kinked phyllite, this one out in the real world, at Thoroughfare Gap, in the Harpers Formation of the … Read more
My student Troy was working on the geologic history of the Thoroughfare Gap regions for his Honors project this semester, and we went out there last week to check out some stuff. One thing I was struck by was how much more deformed these rocks were than I had expected. This was particularly evident in … Read more
I already mentioned the “paddle hackle” that I saw on the field trip I took to Thoroughfare Gap in February. Well, this week I went back out to Throughfare Gap twice, once with a student and once with my fianceé and a friend of ours. I saw cool new plumes both times, decorating joint surfaces … Read more
On the original version of this blog, I showed off a couple of pseudoscorpions that I found under a rock in Montana. On Tuesday, poking around at pollen-ific Thoroughfare Gap with my Honors student Troy, I found another one. Looked like the same thing. See for yourself. I shot a bunch of macro shots with … Read more
Lily and I took a hike yesterday over Old Rag Mountain, a popular destination in Shenandoah National Park. I took the opportunity to shoot a few gigapan images of the scene. If you click on the word “Gigapan” in the lower right of any of these images, it will take you to gigapan.org’s full page … Read more
Another fold seen in the Catoctin Formation, where last week we encountered a very different style of folding — chevrons overprinting Catoctin foliation. Here, we instead have a light colored vein that appears to have been buckled into a semi-ptygmatic form. The trace of the foliation in the Catoctin is discernible, too. Enjoy your Friday!
Last Sunday morning, two of my former GMU students, Aaron and Alan, led a hike for the GMU Geo-Club to Thoroughfare Gap, a water gap in the Bull Run Mountains of Virginia’s eastern Blue Ridge province. I’ve mentioned the Weverton Formation structures we saw there, and a nice example of a hackle fringe in previous … Read more
Callan joins some students from George Mason University on a field trip to the rock exposures at Thoroughfare Gap, Virginia, where meta-sedimentary rocks are exposed in the eastern Blue Ridge province.
Here’s three shots of the Konnarock Formation diamictite, taken with my Nikon microscope. Field of view is about 1 cm in each shot.