It is made up of medium to dark grey laminated greywacke siltstones and mudstones with occasional green beds.

[4] Although most of the Group is unfossiliferous (without fossils), locally sparse graptolite faunas and acritarchs have been found.

Their dating range from the Drumian stage of the Cambrian to the Early-Mid Ordovician.

The Ballymadder Shear Zone (just east of Hook Head on the coast of south County Wexford), separates a to some extent different Cambrian succession immediately to the east to the one to its west.

To its west the Clammers Point Unit (in the Bannow area) exposes a coastal section comprising Cahore Group and Ribband Group sediments.