A reliable age for the Louisburgh-Clare Island succession and its significance in the stabilisation of the Laurentian margin in Ireland

The Louisburgh-Clare Island succession is a sequence of non-marine sedimentary rocks that forms one element of the complex geology along the Fair Head-Clew Bay Line in western Ireland. A first reliable age for the succession is provided by U-Pb dating of zircon from a tuff within the Strake Banded Formation by LA-ICP-MS, giving an age of 423 ± 4Ma (Silurian: Ludfordian or Pridoli). This age indicates that the Louisburgh-Clare Island succession is younger than the other Silurian successions in the west of Ireland. It also better places the succession in a geological history of terrane accretion and basin evolution along the southeast Laurentian margin. The Strake Banded Formation displays a post-Ludfordian cleavage whereas mainly brittle deformation is seen in early to mid-Devonian sedimentary basins along strike.