Due to their similarity and proximity along strike the rocks of Anglesey and the southeast corner of Ireland have long been the subject of comparison. The most frequent correlation is between the sedimentary and metasedimentary successions which lie northwest of the central gneisses in Anglesey and the Rosslare Complex in southeast Ireland. Crimes & Dhonau (1967) considered the Cullens-town Formation to have a correlative in the South Stack Group of Holy Island due to their lithological similarity and comparable complex deformation history. However, Barber & Max (1979) considered the style of deformation and metamorphic grade of the Cullenstown Formation to be more reminiscent of the New Harbour Group.
Until recently the Monian Supergroup in Anglesey was believed to be Precambrian and as such could only be correlated with Precambrian rocks in southeast Ireland. With the recognition of Lower Cambrian microfossils (Muir et al. 1979) in the Gwna Group, there emerged the possibility that much of the Monian Supergroup is Lower Palaeozoic, and thus that correlation may be attempted with younger rocks in southeast Ireland. Recent work in southeast Ireland makes a more detailed comparison between the two areas possible. Much of the stratigraphic terminology used here is newly introduced and will be formally defined in forthcoming papers.
On the basis of lithological correlation it is possible to demonstrate that the Cullenstown Formation is an integral part of the Cambrian Cahore Group (Crimes & Crossley 1968), and that its structure is not incompatable with that developed elsewhere in that group. The