17 April 2015
Fault breccia in Beekmantown limestone
Posted by Callan Bentley
Here’s another sight at the Eocene dikes site in Bluegrass Valley, Virginia, mentioned yesterday:
That’s a gorgeous fault breccia, emplaced parallel to bedding, and parallel to the felsic dike (which can be found a few feet to the west / right of these photos):
It was very poorly lithified, shockingly crumbly to the touch, considering the big slab of rock downhill (to the right) of it.
Here’s a link to the site on Google Maps if you want to visit it yourself.
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.
I once visited a weathered kimberlite dike that looked something like this. Are you sure it is not an intrusive breccia, perhaps powered by volatiles related to the local igneous dikes?
Totally possible. I am not sure about anything. I like your idea a lot – it’s literally five feet away from the felsite sill.