|
KARST
Karst describes a unique type of topography
where limestone bedrock is widely exposed and where surface drainage
is nearly absent and replaced by underground drainage features such
as turloughs, swallow holes and springs. The Burren represents modern
karst where infiltrating acid rainfall is continuing to dissolve
the limestone bedrock and to widen the subterranean channels. However,
many parts of Ireland have undergone similar weathering in the past
when the sea level was much lower than it is today. Therefore, even
where karst features appear to be absent due to the covering of
the bedrock with a layer of glacial deposits, equally well developed
karst may exist at depth especially where the limestone bedrock
has been prone to dissolution in the past.

Limestone on the Rocky Road |
In general, the lower units of
the Carboniferous, namely the ABL and the Waulsortian limestones,
display a much lower level of karstification than the overlying
Burren limestones. This distinction arises from composition and
structural differences between the different formations.
Applying this regional observation
to the proposed road route it is clear that karst features can be
expected from Newmarket-on-Fergus northward to Dromoland. This picture
is consistent with the occurrence of extensive karst at Ennis and
in particular in the vicinity of the Rocky Road where the Burren
type limestone occurs to a large degree.
It is important to note that the
karst features found along the route were developed when the sea
level was much lower than it is today. Therefore, while the bedrock
dips below the estuarine deposits the bedrock here will contain
similar karst features and be in hydraulic continuity with the bedrock
along the proposed route. The estuarine deposits simply overlie
the ancient karst system and represent the modern drainage base
level. |