Dalradian Marble, Maam Valley
Cur Hill, Connemara, Ireland
This area of folded rocks in western Ireland has been described as a structural and metamorphic paradise! Amphibolite facies schists, marbles and amphibolites have been folded together during metamorphism to produce a remarkable array of folds on all scales during the Grampian orogeny.
The distinctive Dalradian rock types (late Precambrian) helped geologists in the 1960’s to unravel the complex structure of Connemara (both older and younger major fold structures are also present) while the meticulous work and dedication of former Society President Bernard Leake led to the production of detailed geological maps for almost the whole of Connemara, together with a Memoir and countless scientific papers. Modern work has shown that the deformation and metamorphism of Connemara formed during a period of just a few million years during the Ordovician, and accompanied a short-lived volcanic arc.
Cur Hill, in the north east of Connemara, is a prominent ridge on the south side of the Maam Valley and provides a section through a synclinorium, with marble occurring on both the north and south flanks of the ridge and in parasitic folds along its length. The spectacular folded marble shown in these images lies on the south side of Cur Hill and is associated with pelitic schists containing staurolite and sillimanite.
The folded marble is remarkably pure with very minor quartz and variable traces of graphite, and this is probably why it displays such perfect similar-style folds. An adjacent outcrop, seldom photographed, has rusty-weathering siliceous layers and much more irregular folding as a result!
Please note that this site is located on private land, please seek information on how to gain access. It is currently a County Geological Site, recommended as a National Heritage Area and must not be hammered.
Text courtesy of Professor Bruce Yardley, University of Leeds
Nominated by Simon Wellings (@metageologist)