Reader Eric Fulmer provided last week’s Friday fold, and this week’s too:
This is also along the banks of the C&O Canal (mile marker 159.5), showing turbiditic strata of the Devonian Brallier Formation, crunched up into a tight fold pair. The Brallier is made of sand, silt, and clay that was shed off the Acadian Orogeny into a neighboring sedimentary basin.
Annotated version:
This deformation, entirely typically of rheologically weak units in the Valley and Ridge, is inferred to have accumulated during late Paleozoic mountain building, when Gondwana (Africa) rammed into North America in an event called the Alleghanian Orogeny.