Faults, intrusions and flood basalts: the Cenozoic structure of the north of Ireland.



Anderson, H.1,2, Walsh, J.J.1 & Cooper, M.R.3
1 - Fault Analysis Group, iCRAG, School of Earth Sciences, University College Dublin.
2 - Midland Valley Exploration Limited, Glasgow, Scotland, G2 1RW.
3 - Geological Survey of Northern Ireland, Colby House, Stranmillis Court, Belfast, BT9 5BF.


Abstract - Detailed digital mapping of the Tellus aero-magnetic data set has revealed the extent and timing of igneous activity in the north of Ireland during the Palaeogene period (c.66–23 million years). These data have provided a unique opportunity to constrain the geometry, scale and development of similarly aged faults in the region. Recognition and analysis of these structures has broadened the understanding of Cenozoic tectonics of Britain and Ireland, with potential implications for fluid flow in hydrocarbon and groundwater reservoirs.
The Tellus data set has allowed detailed structural mapping and analysis to be performed on a regional scale across the north of Ireland. Analysis of the aero-magnetic data has defined five generations of Palaeocene dyke swarms, which, with central igneous complexes and flood basalts, have been used to constrain kilometre-scale displacements on NE-trending sinistral and NNW-trending dextral structures, usually accommodated along pre-existing Carboniferous normal faults and newly formed faults respectively. The results of this analysis suggest a tectonic setting during the Cenozoic in which pulsed Iceland plume-related extension periodically overwhelmed broadly north–south Alpine-attributed compression. These Cenozoic faults sometimes form conductive pathways for subsurface flow, both onshore and offshore of Ireland, with potential implications for hydrocarbon and groundwater exploration and resource management.

In: Unearthed: Impacts of the Tellus Surveys of the North of Ireland. (Edited by Young, M.E.). Royal Irish Academy, Dublin, 180-189, 2016. DOI:10.3318/978-1-908996-88-6.ch14.