Sliabh an Iarainn

Sliabh an Iarainn
Slieve Anierin
Sliabh an Iarainn viewed from Lough Allen.
Highest point
Elevation	585 m (1,919 ft)
Prominence	245 m (804 ft)
Listing	Marilyn
Coordinates	54°5′33.35″N 7°58′19.56″W / 54.0925972°N 7.9721000°W / 54.0925972; -7.9721000Coordinates: 54°5′33.35″N 7°58′19.56″W / 54.0925972°N 7.9721000°W / 54.0925972; -7.9721000
Naming
Translation	Mountain of the iron (Irish)
Geography
Sliabh an Iarainn County Leitrim, Ireland
Climbing
Easiest route	Hike

Sliabh an Iarainn ("mountain of the iron" historically corrupted "Slieve Anierin", and anciently named Sliabh Comaicne) is a large hill in County Leitrim, Ireland, its shape evolving to its present form by ice age glaciers moving southwest over millions of years, the Morainic drift heaping thousands of drumlins in the surrounding lowlands. Irish cultural folklore records strong association with the mythological "Tuatha De Dannan". Sliabh an Iarainn is an important natural heritage site with exposed marine and coastal fauna of paleontological interest

The name Irish: Sliabh an Iarainn, meaning "mountain or moor of the Iron'", originates from an appreciation Iron ore deposits are present. Boate (1652) said "the mountains are so full of this metal, that hereof it hath got in Irish the name of Slew Neren, that is, Mountains of Iron". Sliabh an Iarainn was anciently named "Sliabh Comaicne", the "mountain of the Conmaicne Rein in Connacht". The Irish name spelling is commonly used, though pronounced and corrupted as "Slieve-An-Ierin".

Sliabh an Iarainn is an important natural heritage site due to unbroken sequence of Carboniferous marine fossils present in the rock layers spanning the Namurian (326-315 million years ago) and lower Westphalian (313-304 million years ago) stages of the Silesian (series). The Geological survey of Ireland (1878) wrote “the Geologist may examine all the formations of the district from the Lower Silurian up to the outlier of Coal-measures that crowns Slieve-an-Ierin… It is a rare thing in most countries to find so much comprised in so small a space”.

In her landmark study "The Palaeontology of the Namurian rocks of Slieve Anierin, County Leitrim, Eire", Patricia Yates (1962) demonstrated a "remarkable extent" of Namurian marine fauna bands, abundant with goniatite-Bivalvia, at Sliabh an Iarainn. She described some rock layers as particularly fossiliferous, the shale bands abundant with goniatite faunas and Bivalvia marine and freshwater molluscs. The unfossiliferous shales often contain numerous clay-ironstone bands making conditions intolerable for marine organisms. At most of the fossiliferous levels in the Namurian beds the number of goniatites and Bivalvia are usually very high with the diversity of species low. The richest and most diverse band in the succession at Sliabh an Iarainn, in terms of species present, contains Trilobites, brachiopods, gastropods, echinoids and Bryozoa. Fragments of trilobites occur abundantly at particular bands. Overall, Yates documented nearly 120 distinct fossiliferous sites around Sliabh an Iarainn, her work complimented by extensive photographs of often beautifully preserved fossils. Her study of Sliabh an Iarainn is considered important, being housed at the Murchison Museum, Imperial College, British Geological Survey Museum, and the Natural Museum in London.