23/10/2023
Benbulben geology
Benbulben was shaped during the ice age, when Ireland was under glaciers. Originally it was a large plateau. Glaciers moving from the northeast to southwest shaped it into its present distinct formation. Benbulbin, and the Dartry Mountains as a whole, are composed of limestones on top of mudstones. These rocks formed in the area approximately 345-330 million years ago in the Viséan Stage of the Carboniferous Period. The environment was a shallow sea. Uppermost in the limestone layer is a thicker, harder limestone called the Dartry Limestone Formation. Below this is a thinner transitional limestone formation – the Glencar Limestone Formation. Further down, the lower slopes consist of shaly mudstone known as the Benbulben Shale Formation. Scree deposits are found near the base.
Fossils exist throughout the layers of the mountains. All layers have many fossilised sea shells. The shale layer also holds some corals.
Baryte was mined at Glencarbury near Benbulbin in the Dartry range between 1894 and 1979
