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15 September 2023
Friday fold: Candler Formation
On a birding hike yesterday morning, I found this: This is a little slab of kinked phyllite of the Candler Formation. This metamorphic rock started as mud (and ash) deposited atop the Catoctin Formation, and it was later squeezed and heated during Appalachian mountain-building, encouraging the growth of micas at the expense of clay. A strong differential stress made sure those micas grew in one preferred orientation, and that resulted …
9 June 2023
Friday fold: Pleasant Grove Park
Happy Friday, friends. Here’s a rock sample that I recently polished up: It shows crenulations in “pinstriped” schist of the western Piedmont in Pleasant Grove Park in Fluvanna County, mapped as the Mine Run Complex. Lovely stuff, eh?
7 June 2023
The unconformity gets its portrait taken
Callan recounts a little lesson in taking a photograph of an outcrop that expresses itself more readily to the novice eye.
21 February 2023
Recent rocks
Trying to dredge up some blogging inspiration, but honestly I’m feeling underrested and overworked these days, and not particularly enthusiastic about writing. But here are some cool rocks I’ve seen lately; maybe you’ll find them interesting… Antietam Formation quartzite at Sherando Lake, Virginia: I was struck by how sugary the texture was, and the interesting joint patterns resulting in kind of bulbous forms. Graded bed of bioclastic debris, Martinsburg …
2 December 2022
Friday fold: Hidden Rock Park, Goochland County
Two weeks ago was the annual Virginia Geological Field Conference, which was centered this year on the Goochland Terrane, an interesting block of crust in the Piedmont which shows some similarities to the Blue Ridge geologic province, but also shows some differences that suggest it’s not just a mini-Blue-Ridge. One of the best exposures was in Hidden Rock Park, where a series of “whaleback” outcrops expose things like this: There, …
16 September 2022
Friday fold: isoclinal limestone near Harrisonburg
This weekend, my family and I traveled to a little agrotainment complex north of Harrisonburg, Virginia, a joint called Back Home On The Farm. It featured a corn maze, hayrides, petting zoo, apple cider donuts, and pumpkin picking. All typical fall frolic; good clean fun. But there were also big blocks of limestone everywhere on the property. I did my best to check them all out. I was mainly scanning …
18 August 2022
Quarrying soapstone
Earlier this summer, I was lucky enough to visit a soapstone quarrying operation in Schuyler, Virginia, right on the Albemarle/Nelson County line. These soapstone bodies are metamorphosed ultramafic intrusions into the Neoproterozoic sedimentary deposits of the Lynchburg Group. The protolith peridotite sill crystallized at ~580 Ma, meaning the host sediments are older than that (but younger than the Grenvillian basement complex that underlies both). Then both plutonic rock and sedimentary …
24 June 2022
Friday fold: Kinked Lynchburg metasediments near a soapstone body
Happy Friday! Here are some kink-folded metasediments from Virginia’s Lynchburg Group to help usher in the weekend.
6 November 2021
Revisiting Tinker Creek
While my son takes banjo lessons downtown, I stroll Charlottesville’s walking mall and browse the bookstores. Last week, I dropped $40 at one of the used-book stores, walking away with an armful of volumes. Most were intended for my son (a voracious reader in addition to being banjo-philic), but on the shelf I also saw a trade paperback copy of Pilgrim at Tinker Creek, by Annie Dillard (1974), a book …
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.