Back-shoal patch reefs in latest Early Cambrian (local stages Bilbilian to Leonian).
boundstones predominantly composed of archaeocyaths (branching colonies of Archaeocyathus and solitary Pycnoidocyathus) in growth position overgrown by a framework of Epiphyton, Renalcis and Girvanella. Reefal debris with quartz silt.
Some archaecyathan floatstones with up to 20% of terrigeneous material.