- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
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.