THE ORDOVICIAN BIOGEOGRAPHY OF THE GRANGEGEETH TERRANE AND THE IAPETUS SUTURE ZONE IN EASTERN IRELAND

The Caradoc trilobite and brachiopod faunas of the Grangegeeth terrane show marked Scoto-Appalachian/Laurentian affinities. Contrary to some plate tectonic models, this indicates that the terrane must lie to the north of the Iapetus suture. More limited graptolite evidence from the Llanvirn of Grangegeeth suggests that the terrane may have been closer to the Gondwanan margin or at least at higher latitudes earlier in the Ordovician and migrated to low latitudes prior to its eventual accretion onto the Laurentian margin.