Evidence of ancient desert environments discovered on Ireland’s highest mountain
It must now be more than a year since I found this photograph of ancient ripple marks. The fossilized marks seen on the red sandstone which covers pretty much the entire southern part of County Kerry isn’t anything unusual. What makes it unusual and very special is that you can see them on the top of the highest mountain in Ireland. When you climb to the summit, you can imagine walking on an ancient river bed!
This is the story of its discovery which took place not so long ago and was the beginning of my Mountain Geology research.
In August 2015, Michael Maunsell, a scientist with an interest in mountain ecosystems, climbed ‘Howling Ridge’ on Carrauntoohil to investigate some geological features which occur in the area. On the summit ridge, Michael carried out the first ever survey and record of the small–scale, wave-generated ripple marks on some of the slabs of rock on the ridge between the peaks of Carrauntoohil (1038.6m) and Beenkeragh (1008m).
The ripple mark are evidence that these rocks, near the highest point in Ireland, were formed due to the deposition of sediment (sand, in this case) by river systems in a relatively flat, desert like environment, between 410 – 355 million years ago, when Ireland was located below the equator. Since then, the Old Red Sandstone has been folded by huge forces, so much so, that the sandstone which was once laid down horizontally, is now standing almost upright in places, resulting in the Ireland’s highest mountain range, the MacGillycuddy Reeks and other sandstone mountain ranges across Southern Ireland.
Michael explained that by examining the ripple patterns and the shape of the ripples, we can tell the direction of flow of the current which formed them millions of years ago. The upstream or “stoss” side of the ripple is exposed to the full brunt of the current, and is a site of erosion. The downstream or “lee” side of the ripple is in the “current shadow” and has slightly less energetic water conditions. As a consequence, sand can settle in these slightly protected circumstances, accumulating on the downstream face of the ripple. Michael said that while standing on the exposed on the Beenkeragh ridge, “I wondered how these ancient ripple features, the highest ripples in Ireland, had survived successive period of glaciation, which had been so destructive in this area and could grind even the hardest granite of other mountains to a smooth surface”.
Special thanks to Mike Maunsell, lecturer in Conservation & Biodiversity Management and founder of Mountain Research Ireland, which works to protect Ireland’s Mountain environments through research and collaboration, who kindly shared his knowledge and experience with me.