The Ballantrae ophiolite complex was probably an island-arc-marginal–basin assemblage that formed and was thrust onto a pre-Caledonian continent between 490 and 470 m.y. ago; only a brief time separated the birth and death of this marginal basin. Middle Arenig is dated at about 480 m.y. B.P., and therefore the idea of a pre-Arenig Dalradian structural evolution can be extended from Ireland to Scotland. The time of opening and closure of this marginal basin is marked in the Dalradian rocks to the north by mafic igneous intrusions, D3 deformation, and a change in the nature of the plutonic activity.