The Burren Field Trip - 23rd - 25th April 1999 Based in the Admiral's Rest in Fanore on the coast opposite the Aran Islands

The field trip to the Burren in April led by Bettie Higgs was a roaring success with a record attendance of 20 enthusiasts (and beginners). During the weekend we explored the geological history of this special place, following the changes in sedimentation and environment from the Lower to the Upper Carboniferous.

Mulloghmore mountain and the thurlough in the foreground was the proposed site of an interpretive centre. Clints and grykes are visible in the foreground.

Black Head, at the lighthouse, was the first port of call on the Saturday morning. Here we had our first close look at the extensive formation which stretches for many miles in this area. Some preliminary tests were carried out to confirm (just in case the experts had been wrong all these years) that this was in fact limestone. The rocks were tested with a little drip of hydrochloric acid and fizzed merrily as expected. Two good joint sets meant that the clints and grikes were plentiful, the most prominent direction being 020. We measured a slight degree of dip to the south in these limestone beds. Closer to the sea were darker coloured rocks in which the calcium (of the calcium carbonates) had been replaced by magnesium to form dolomitic limestones. The ‘acid’ test produced a negative result here. A thin band of dolomite was also found just above the road. Several granite erratics were observed in this area the source of which was possibly the Galway/Connemara granites. Just across the road from the lighthouse we found some cerioid lithostrotion corals which are an important biostratigraphic marker confirming the Visean age of these rocks. Our next stop at Murragh, 1km to the South at a large calcite vein, just over the wall on the landward side of the road. The vein contained large calcite crystals with their three cleavage planes clearly visible. The orientation of the vein was measured (while mostly avoiding the cowpats) and found to be parallel to the main joint set.

At Ailledie North we stopped to examine a clay ‘wayboard’ at the base of the terraced limestones. Although this was obscured in some places by glacial till, there were areas where it was clearly visible if you got down on your knees and poked around. This clay could represent a fossil soil formed during a period of emergence. The limestone beds above the clay contained large brachiopods. At Ailledie South, a fossil fanatic’s paradise, we found on some of the exposed bedding planes many fine examples of rugose coral colonies of Siphonodendron. There were also beautiful examples of solitary corals, sponges, crinoid stems and bryozoans. Just further along at this site was a spectacular blowhole, part of which looked like a manmade bridge, but on closer inspection proved to be well eroded limestone. A calcite vein adjacent to the blowhole was found to strike in the same direction, and be in line with, the one seen at Murragh Going south at the base of Ballynalackan Castle we saw a good example of a dry valley. The scenery and vegetation changed abruptly as we travelled south, and just outside Lisdoonvarna at Murphy’s Bridge and Spectacle Bridge we found ‘bullions’ in the form of disc shaped iron nodules of siderite in the Clare shales. Nearby, at St Brendan’s Well, the shale/limestone boundary was exposed, producing a small inlier. The shales here contained abundant goniatites and brachiopods, confirming the Namurian age of the rocks.

At Fisherstreet Strand in Doolin we explored the cliffs which had unfossiliferous shales at the base containing iron pyrites formed in anoxic conditions. Just above this was a goniatite marine band. Further south we climbed the cliff to examine the top of the overlying Gull Island Formation. Here we saw slumped siltstones and sandstones and several impressive sand volcanoes. There were also ripple marks and flute casts here which have led geologists to suggest that the source was to the West in Namurian times. From here our last stop was the Cliffs of Moher where we were treated to some magnificent views, and to the sight of the famous Liscannor flagstones with their trace fossil worm burrows, albeit out of situ. The young budding geologist John Leahy Junior also managed to find some specimens of the bivalve dunbarella Many thanks to Bettie Higgs for a very enjoyable and informative trip. Bettie managed to impart a great deal of knowledge in a short space of time explaining the various aspects of local geology and putting it into a regional context.

John Deykin Cliffs of Moher showing bands of limestone and shale