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Ballycastle CoalfieldAntrim
Summary Full report
Site Type: Coastal section
Site Status: PASSI
District: Moyle District Council
Grid Reference: D133414, D164426
Rock Age: Carboniferous (Namurian, Visean)
Rock Name: Ballyvoy Coals, Bath Lodge Coal, Carrickmore Black Band Ironstone, Hawk's Nest Coal, Main Coal (No08), Main Limestone (No08), Mcgildowneys Marine Band, Splint Coal, Wee Coal
Rock Type: Coal, Lava, Limestone, Sand, Sandstone
Fossil Groups: Brachiopod, Crinoid
Other interest: No data, No Data

Summary of site:

The Ballycastle Coalfield was the final area of commercial coal extraction in Northern Ireland, the last mine closing in 1967. The setting is particularly arresting since almost all the major workings exploited the impressive coastal cliffs. The coal seams were continuously exposed in the cliffs and adits were driven southwards into the cliff face to exploit the northerly tilt of the rocks. This mining method created natural inclines towards the mine mouths, easing coal extraction and drainage.

The topmost rocks in this coastal section are seen in the cliff above a raised beach set back from the coastal cliff at Bath Lodge. From here the rocks extend along the coast to the east for 3.5km. A series of faults divides the cliff into blocks which step down relative to each other to the west in all but a few cases. The effect along the coast is often to repeat the same sequence of rocks but there is a gradual exposure of lower, older, rocks to the east. In all, a thickness of some 250m of Carboniferous sediments can be seen along this coastline, out of an estimated total thickness of 700m. The succession is dominated by sandstones and shales, with the occasional limestone and coal seam. The coals were generally of poor quality and ranged in thickness from less than 0.5m up to 1.4m. The seams (from the top down) were the Bath Lodge Coal, Splint Coal, Hawk’s Nest Coal, Main Coal, Wee Coal, Middle Till and Stronbane Coal. The general geological picture is of a subsiding coastal basin filling with deltas clothed in forests. The trees were killed by periodic inundations of sea water. There are three obvious marine deposits: McGildowney’s Marine Band occurs between the Hawk’s Nest and Main Coals; the Carrickmore Marine Band is at the very bottom of the exposed section; and the Main Limestone below the Middle Till has a good marine fauna. The succession spans the boundary between the Viséan rocks and the Namurian measures above but the exact boundary is not defined. The Main Limestone is definitely Viséan (probably of Brigantian age) and the base of the Namurian is arbitrarily set at the Main Coal. Fossils in McGildowney’s Marine Band (above the Main Coal) give a clear Namurian age. Up to six Carboniferous lava flows are exposed in the cliffs south of Bath Lodge. They are on the south side of the Great Gaw fault which has lifted them around 400m from depths well below the rocks seen along the coast. Several Tertiary dykes cut the cliffs and foreshore (including the famous North Star Dyke) and, beyond the car park that terminates the coast road, the cliffs are capped by the 20m thick Gobb Sill for about 1km. These Tertiary intrusive rocks are associated with the massive Fair Head Sill immediately to the east. This once despoiled industrial coastline has now softened into an impressive series of coastal cliffs demonstrating the unique deltaic formation containing the earliest commercial coals in Ireland. Its complex sedimentary features, combined with its Carboniferous lavas and Tertiary igneous intrusions displayed along an actively eroding rocky shore, create a natural classroom of exceptional diversity.

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