Plumose marking or Plume Structure
A quick blog on
Plumose markings or Plume structure
Joint surfaces are sometimes have characteristic surface markings. They are of two types Hackle marks and Rib Marks. Plumose or Plume structure is the most common type of Hackle mark. They are feather like markings on the joint surface with a central axis from which the rays or barbs branch out into either side.
According to Parker 1942 plume structures are common on shear joints while they are rare in conjugate joints.
All these photos are taken by me and are from Lunavada, Gujarat, India. You can easily find many such outcrops on Ahmedabad zalod highways road cut sections.