By: magic-gigapans
Image: Chris Johnson, Mid-Atlantic Geo-Image Collection
License: Creative Commons Non Commercial ⧉

Uploaded: 13 May 2020
Last Updated: 19 May 2020

548 megapixels
30,064 x 18,220 pixels
100.2 in X 60.7 in at 300dpi

This amazing piece of float was located under the Route 15 Bridge in Point of Rocks, MD. My current thinking is that the lower left corner is Catoctin formation but I am scratching my head over the upper right portion. Perhaps it is also Catoctin Metabasalt just with a different, more rigid consistancy. However, the presence of micas and what look like sand sized grains suggests that this may not be the case. Or is it a lense of some sort of sandy mudstone within the Catoctin? A litte bit of research showed that the Loudoun Formation (a pyroclastic unit) overlies the Catoctin Formation discontinuously in Maryland. So does this piece show the Catoctin-Loudoun Contact? Or, another explanation is that it could be a silty expression of the Weaverton (which overlies the Catoctin formation where the Loudoun Formation is mission). Or, I could be completely wrong. Anyhow, I am open to suggestions and the Description will be updated when I can come up with a more satisfactory explanation.