Younger Ordovician reefal carbonates along the Moiero River include late Ashgill (?Hirnantian), 1-2m high, stromatoporoid-calcimicrobial patch reefs, associated with phosphorite gravels.
The capping Silurian bituminous micrites are graptolitic  (Climacograptus, Pristiograptus), marking a flooding surface.