Abstract - Fault and fracture systems are the most important store and pathway
for groundwater in Ireland’s bedrock aquifers, either directly as conductive flow structures,
or indirectly as the locus for the development of dolomitised limestone and karst. This article
presents the preliminary
results of a study involving the quantitative analysis of fault and fracture systems in
the broad range of Irish bedrock types and a consideration of their impact on groundwater
flow. The principal aims of the project are to develop generic conceptual models for different
fault/fracture systems in different lithologies and at different depths, and to link them to
observed groundwater behaviour. Here we briefly describe the geometrical characteristics of
the main post-Devonian fault/fracture systems controlling groundwater flow from field
observations at outcrops, quarries and mines. The structures range from Lower Carboniferous
normal faults through to Variscan-related faults and veins, with the most recent structures
including Tertiary strike-slip faults and ubiquitous uplift-related joint systems. The
geometrical characteristics of different fault/fracture systems combined with observations
of groundwater behaviour in both quarry and mine localities, can be linked to general flow
and transport conceptualisations of Irish fractured bedrock. Most importantly they also
provide a basis for relating groundwater flow to particular fault/fracture systems and
their expression with depth and within different lithological sequences, as well as their
regional variability.
GSI Groundwater Newsletter, 51, 28-33, 2013.