One of my favourite road cuts is the big swaley crossbedding on I-40 as you near the top of the Cumberland Plateau.
Rock talk
This isn’t that cut, but one along Highway 68 in Rhea County, Tennessee in what I had always thought was the Crab Orchard formation. Here’s the link to the original image by Chuck Sutherland who kindly granted me permission to build on his work.
Crab Orchard sandstone is much used and beloved in Mid-South gardens and an essential feature of some of the most beautiful and dramatic Tennessee landscapes. I had been told that was the name of the geological formation, by more than one geologist. I was telling my man all about it, and he just went and looked it up. He tells me the Crab Orchard formation is described as “composed mainly of greenish-gray clay shale with minor amounts of dolomite” (USGS link) and Silurian in age. Now, I know I’ve taken some artistic liberties here, but does that look like shale to you? It turns out it’s the Crab Orchard Mountains Group, most likely, although there is an underlying Gizzard Group with some similar lithology (USGS link). These are younger rocks, Carboniferous in age. Pennsylvanian to be precise, but don’t tell my man. As a British Geologist he says there’s no such thing as Pennsylvanian or Mississippian. I know, I know, but he does the laundry and most of the driving, so I overlook his foibles.
Art talk
I’ve always wanted an image of the Crab Orchard formation’s big crossbedding, which if you’ve read the section above, you know doesn’t actually exist. And neither do many artworks of rocks that delight my lapsed-geologist’s eye. So I decided to make one. Chuck Sutherland has the eye for the geology and an artistic eye, too – so I was thrilled when I found his website. As a Tennessean far from home, they’re a wonderful reminder of our state’s natural beauty and I love that there’s a big overlap on what we seem to find beautiful and interesting. The wealth of detail was perfect for etching and I happened to be taking a drypoint etching class. OK, so it’s not the most perfect example of crossbedding, given the weathering on this roadcut, but it reminded me of driving down Tennessee highways. The use of chine colle watercolor gives it that dreamy softness of memory and a home far away.
I was a little rushed and the paper I used was perhaps a little thick and wet, so there is some bleeding of the waterbased ink (on the right-hand side of the image, mostly cropped out). But perhaps it gives it an even more dreamlike feel? Or maybe that’s the Crab Orchard shale trying to make an appearance.
