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:
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?
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…