3 May 2013
Last weekend, after we checked Lily in for her race, I spotted some boulders near the check-in site. The next morning, once the race had started but before we could cheer her on, my field assistant and I went back to the boulders to check them out.
My field assistant’s planners had forgotten to pack him a hat – so we improvised with a pair of fleece pants inverted on his noggin:
We were glad to have gotten back to take a closer look at these boulders, which showed limestone and dolostone layers that had been both cleaved and strongly folded.
There was one array of en echelon tension gashes, too.
Look at these lovely folds! They reminded me very much of some folds I saw last summer in Yoho National Park, British Columbia.
In some layers, my field assistant and I spotted limy rip-up clasts:
In some places, these rip-up clasts had been thoroughly distorted (and aligned) through compressional strain:
The differential weathering between the dolostone layers and the limestone was obvious and profound:
Another boulder showed this even more elegantly, and the dolostone was a rich, caramel color to boot!
My field assistant and I were very pleased with what we found. Though these boulders were not in situ, I suspect they are from the Conococheague Formation, which exhibits similar lime/dolostone interlayering. And that does crop out nearby.
My field assistant reminded me it was time to go cheer on mommy as she ran past mile marker 5, so we skeedaddled, right after I made him pose for one more shot…