Heritage Sites of Co. Clare
The Daniel O’Connell Monument, Ennis
This monument commemorates the great nineteenth century nationalist leader Daniel O’Connell and celebrates the former Clare MP’s role in delivering Catholic Emancipation. The 67 ft high Doric column on which the statue stands was erected by William Carroll between 1859 and 1863. The O’Connell statue was carved out of a single block of Ballinasloe limestone by sculptor James Cahill of Dublin between 1861 and 1865. The pale grey, crystalline Carboniferous limestone, packed with crinoidal stem fragments, was a popular nineteenth-century building stone. The large and extensively worked quarries were situated at Brackernagh (Clancarty) on the Earl of Clancarty’s Estate, just southwest of the town of Ballinasloe.
Geology of Co. Clare
The geology of County Clare can be conveniently divided into three regions. In the east of the county Silurian sediments, deposited in a shallow sea about 440 million years ago [Ma], are surrounded by Devonian sandstones (415 to 360 Ma), laid down when the region was land. Rising sea level in the early Carboniferous, around 360 Ma, drowned the Devonian landmass and deposited a great thickness of limestone, now so clearly exposed across the Burren and beneath the lowlands to the east. Later in the Carboniferous, around 320 Ma,
rivers flowing from the south-west built deltas into this shallow sea. As more and more sand and mud was deposited on these deltas, they often became unstable. Sometimes enormous volumes of sediment slumped down into deeper water, breaking and folding the still soft layers as it went. These delta sediments, and some of the spectacular slump folding in them, are superbly exposed in the cliffs of south-west Clare.
During the Ice Age, of the last 2 Ma or so, the glaciers and ice sheets stripped away much of the shale and soil cover on the limestone. Exposed to the high rainfall of the west of Ireland, the limestone has been slowly dissolved both above ground and below in a process called karstification. The Burren is a classic karst landscape where all or most of the river drainage is underground. Similar landscapes include Croatia and Yorkshire. When the ice of the last Ice Age melted the water carved out great caverns deep in the limestone as it descended down cracks in the rocks. Now rain water may widen the joints and cracks on the surface (called clints and grykes) and streams disappear underground through swallow holes. Ailwee Cave is an extensive cave system that once was the home to Brown bears 9,000 years ago. As water dripped through caves calcium carbonate was sometimes deposited as stalactites (pointing downwards) or stalagmites (pointing upwards), which may merge to form a column. Occasionally large deep circular depressions called poljes form by solution. At Carran this feature is 200 feet deep and one mile long. Dry river valleys are a common feature of the Burren when the water has disappeared underground. The Cahir River is the only over ground river in the Burren and it flows over glacial till that is impervious.
Some of the Upper Carboniferous rocks contain fossils. Goniatites are small coiled shelled relatives of the squid that are found in the marine shales; however the flagstones quarried at Liscannor are more widely known. These contain trace fossils or tracks called Olivellites (pictured right) that meander across the surface and produce a beautiful pattern. The muddy sand across which they moved was deposited in deepish water and small arthropods burrowed through it in the search for food. While the burrows have been preserved there is no sign of the organism that made them. As the rock contains flecks of the silvery mineral mica it can be easily split and was once used for roofing, and now for decorative paving.
Suggested Reading: Exploring the limestone landscapes of the Burren and the Gort Lowlands (2006) Mike Simms, Belfast.
Map legend: Geological Map of Limerick (based on GSI 1:1,000,000 map 2003). Pink: Ordovician; Pale green: Silurian; Beige: Devonian sandstones; Light blue: Lower Carboniferous limestone; Dark green: Upper Carboniferous shales and sandstones.