22 November 2014
Stylolites in Helderberg crinoidal grainstones, Corridor H
Posted by Callan Bentley
Long week, no blog.
But, hey – it’s Saturday, and I have a couple of hours of breathing room – so here are some stylolites in a crinoidal grainstrone in the New Creek member of the Helderberg Formation, exposed on Corridor H in West Virginia.
Stylolites are pressure solution features, which overall form perpendicular to the maximum squeezing direction (maximum principal stress direction, σ1), and have little wiggle peaks that point in the maximum stress direction. So when a geologist sees this…
…they interpret it this way:
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.
Callan,
Nice illustration of a classic example from a great field trip. The pink/gray color contrast on either side of the stylolite is quite striking. Do you know its origin?
Hi Bob!
It’s different bedding compositions, being brought into close (direct) proximity due to intervening pressure solution along the stylolite surface. Slightly different flavors of crinoidal grainstone being forced into intimacy as the former buffer zone trickled away…
C