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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 …
16 August 2022
Kinked metavolcanics of the Castine Formation, eastern Maine
Callan shares a few outcrops from coastal Maine, part of the Avalonia terrane that accreted to ancestral North America during the Acadian Orogeny. They are volcaniclastic rocks, coarse and fine, and showing both overprinting kink bands and cross-cutting basaltic dikes.
1 July 2022
Friday fold: lithified python
A quick Friday fold that I observed last month in a boulder of riprap at Chippokes State Park in Surry, Virginia. I have absolutely no idea where this rock was quarried; but it doesn’t look like anything I’m familiar with in Virginia, so maybe the Baltimore Mafic Complex??? Anyhow, it’s not native to the Coastal Plain, but it shows a pleasing fold train of green and gray amid the black …
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.
29 May 2022
Accretionary wedge turbidites from the Lost Coast
The Lost Coast of northern California shows geological evidence of deep sea turbidity current sedimentation, tectonic accretion during Mesozoic subduction, and then isostatic uplift interacting with shoreline erosion. Check out a few photographs taken by Callan’s wife on a recent backpacking trip through the region.
15 April 2022
Friday fold: Cretaceous Canada
A guest contribution for the Friday fold, from reader Christian Gronau: Christian reports that this is located on the North side of Hwy.11, 20 miles east of Saskatchewan River Crossing, Alberta. Eastern foothills of the Canadian Rocky Mountains. Faulting and folding in Early Cretaceous Luscar Group sediments. Typical repeating sequence of sandstone, siltstone and coal. Thanks for pitching in, Christian! Happy Friday to all!
12 November 2021
Friday fold: Raven’s Ridge
Happy Friday, all! Two shots today from my friend Joe up in Vermont. He sends these from the Champlain Valley, at a place called Raven’s Ridge. It looks like an alternating series of sandstones and shales, arched into an anticline, perhaps during the Acadian Orogeny (??). According to the Nature Conservancy’s website, porcupines live in this anticline, which is called “The Oven.” Looks like most of the strata around there …
25 June 2021
Friday fold: The Blue Ridge Tunnel
Inside the Blue Ridge (in an 1850s-era railroad tunnel), Callan finds folds and boudinage that formed during Appalachian mountain-building.
11 June 2021
Friday fold: inadvertent kink fold analogue model
It’s Friday! Adam Forte, a geology professor at LSU, posted this image yesterday on Twitter: It’s a box of sheets of newsprint, stored vertically and ignored for a while, now rotated 90° so we’re looking at a cross-sectional view. To me, this is an excellent example of a physical analogue modelling experiment (albeit inadvertent) that demonstrates the process by which kink folds form. The key parameters to get this distinctive …