Quantitative analysis of Cenozoic faults and fractures and their impact on groundwater flow in the bedrock aquifers of Ireland

Abstract Faults and fractures are a critical store pathway for groundwater in Ireland’s limestone bedrock aquifers either directly as conductive structures or indirectly the locus development of karst conduits. From quantitative analysis post-Devonian faults range lithological sequences, this report describes principal characteristics Cenozoic strike-slip joints, youngest most intrinsically within Irish bedrock. Analysis these more than 120 outcrop, quarry, mine cave locations types, provides basis for: (1) definition models their depth dependency, control, scaling systematics links to preexisting structure, (2) conceptualisation impact on behaviour, (3) estimation flow parameters. The provide constraints fracture-controlled connectivity. Commonly observed decreases sustainable flows water strike interceptions with attributed increasing confinement decreasing fracture connectivity dissolution. joints have quite different end member geometries, having strongly heterogeneous scale-independent properties often showing scale-dependent stratabound properties. highest usually associated complexity structure Carboniferous (on which fracturing localises), enhanced by karstification jointed particularly near-surface. Increased is promoted bedded, rather massive (i.e. unbedded), characterised bedding-parallel connecting otherwise subvertical wells.