The Sutton Stone: an Early Jurassic rocky shore deposit in South Wales

The unconformity between Jurassic and Carboniferous carbonates at Southerndown, near Ogmore-by-Sea, Mid-Glamorgan, represents an ancient rocky shoreline which has had a long history of study. Henry De la Beche discussed the ecological details of the unconformity surface, but subsequent debates focused more on the age and depositional setting of the basal Jurassic conglomerate known as the Sutton Stone. Our contribution returns to the theme of faunal development on the unconformity surface. The Jurassic corals, Allocoeniopsis gibbosa and Heterastraea sp., occur as encrusters of the Carboniferous substrate on a tidal abrasion platform. Serpulid-worm colonies may be observed in life position above the stepped unconformity, but not attached to it. These and other features of a physical and biological nature suggest sporadic preservation in rapidly changing ecological settings during an Early Jurassic marine transgression.