Southeast of Charlestown, western Ireland, Ordovician tuffs, agglomerates, and lavas are interbedded with cherty shales. A graptolite fauna in the cherty shale contains Didymograptus, Isograptus, Tetragraptus, Glossograptus, Oncograptus, and Phyllograptus? and indicates an Arenig (Ordovician) age.