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28 July 2011
A faulted chert nodule
Here is a trio of concentrically-zoned chert nodules in Mississippian Castle Reef Dolostone, exposed at Sun River Canyon, Montana, just downstream from the roadside outcrop of the French Thrust: If you look closely at the lowermost of the three chert nodules, you’ll see it’s been split and offset by a small fault. Here are close-up portraits of all three, concluding with the most interesting one (the deformed one): Hope all …
30 October 2010
Orbs in the floor
Happy Saturday morning, everyone. I’m on my way down to the National Mall for fellow Tribesman Jon Stewart’s “Restoring Sanity” rally, but I thought I would just quickly post a little geological treat for Mountain Beltway readers. These are pisolites (basically like a big oolite, but without the biological component that would qualify them as oncolites), as seen in the travertine panels that make up the floor of the conference …
18 September 2010
Guest concretion
This was brought in last week by a student… It’s a broken concretion that she found in Des Moines County, Iowa, many years ago. She also had a slab of limestone with crinoid columnal fossils, and a broken geode from the same locality. I think this concretion is a thing of beauty, like a fossilized Gobstopper. I had to photograph it before I gave it back to her.
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.