The geology of the Kilbride Peninsula and adjacent areas, County Mayo, and its gignificance for regional geological models

Abstract:A new geological map and a partly revised lithostratigraphy are presented for the Kilbride Peninsula and the area immediately to the north in County Mayo in the west of Ireland. Volcanic arc rocks of the Lough Nafooey Group are unconformably overlain by late Floian mudrocks that were deposited after the cessation of volcanic activity and which did not receive any detritus from the Lough Nafooey arc. The unconformably overlying Darriwillian Rosroe Formation is similar in character to areas immediately to the west and north-east and shows a coarsening upward pattern. A south dipping Silurian succession everywhere masks the contact between the Lough Nafooey Group and the metamorphic rocks of Connemara. The Silurian succession shows progressive deepening from terrestrial sediments at the base to deep-water turbidites in the youngest strata seen. There are also important provenance changes throughout the Silurian succession. A widespread alkaline lava near the base is the only thick volcanic horizon seen in the succession. The structural geometry suggests that two large fault features (the Doon Rock and Clonbur faults) acted as a linked system during sedimentation and may have produced a point source for a clastic sediment fan of latest Ordovician or early Silurian age. This feature, termed the Derryveeny fan, contains coarse-grained metamorphic detritus from erosion of Connemara further to the south. A marked strike swing of the Silurian strata is attributed to post-Wenlock SSE directed contraction with reverse reactivation of the Derry Bay and Lettereeneen faults and associated deformation of their respective footwalls.This is an open access article under the terms of the Creative Commons attribution license, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Open Access funding provided by IReL.