4 March 2016
Happy Friday, everyone. Today, Joe Kopera takes us to the summit of Mount Monadnock, in New Hampshire, to show us “the Billings fold.”
This locally famous recumbent fold is a favorite teaching spot on the southern face of Mt. Monadnock, southern New Hampshire’s most prominent peak. The recumbent fold deforms turbiditic graded bedding in the Devonian Littleton formation and is associated with a bedding-parallel cleavage. It’s still debated as to whether or not this fold is related to, and is itself, early nappe-style folding during the Devonian Acadian Orogeny. Look to the lower left of the fold hinge for a rotated boudin train parallel to the axial trace of the fold, highlighting the strain direction that caused the fold.
You can explore bigger versions of this image at Joe’s Flickr page. What an excellent fold – I hope to visit it in person some day. Thanks for the contribution, Joe!
Remember, any reader is welcome to submit fold imagery for this weekly feature. I welcome your contributions.