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Earth Science Conservation Review
| Ballycastle Coalfield | Antrim |
| Site number: | 19 | File Number: | D14 |
| ESCC: | EC | ||
| Locality Type: | Coastal section | Status: | ASSI |
| Grid Reference: | D133414,D164426 End(s) of linear site, Not Entered | ||
| Google maps: | 55.20711,-6.22028 | ||
| County: | Antrim | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Carboniferous | ||
| Stages: | Namurian, Visean | ||
| Lithostrat: | 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 | ||
| Site Description | |
|---|---|
| Highlights: | |
Coastal exposures of some 400m of Visean and Namurian sediments and contemporaneous lavas. The best displayed coalfield sequence in Ireland, exposed on tidal rock platforms and cliff sections. | |
| Introduction: | |
The coast from the eastern end of Ballycastle Bay (D133414) to Carrickmore (D164426), a distance of over 3km, offers an uninterrupted section through the uppermost part of the local succession of Carboniferous rocks, including several coals which have been worked in the past as the 'Ballycastle Coalfield'. As the coals cropped out on the coastal cliff they have been worked from very early times, certainly from the sixteenth century at least. East of Carrickmore the massive block scree below Fair Head obscures most of the lower part of the succession but small outcrops in the scree and in Murlough Bay show a group of volcanic tuffs and lavas. The lowest beds in Carboniferous succession in the area are seen in small stream sections south of the Great Gaw (fault) which cuts the productive coalfield off from the underlying coarse sediments about 1km south of the coastal exposures. The whole Carboniferous basin rests unconformably on the Dalradian metamorphic rocks of the North- East Antrim ridge and corresponds closely to the Machrihanish Coalfield in Kintyre, 40km to the north-east. Apart from the Carboniferous rocks there are several Tertiary intrusive igneous features in the area; sills and dykes of basalt and dolerite intruding the earlier sediments. The outcrops of coal seams on the sea cliffs and foreshore excited interest since early times and references to the coalfield in the literature date back to 1733; accounts of the geology start with Hamilton in 1786 and are followed by Griffith (1829), Kelly (1868) and three consecutive investigations by the Geological Survey, Symes et al. (1888), Wright (1924) and Wilson and Robbie (1966). | |
| Description: | |
As the coalfield is divided into a number of blocks by a series of NNE-trending faults, mainly downthrowing to the west, the general south-easterly dip of the beds along the east-north- easterly line of the coast tends to raise the level of individual horizons to the east. The aggregate effect is to maintain the level of individual strata and the same beds are repeated along the coastal exposures, within a variance of a few tens of metres, as far as Carrickmore. The highest beds seen in the Carboniferous succession, the Upper Coal Group, occur in the raised beach cliff south of Bath Lodge, where a poorly exposed series of grey sandstones and shales includes a 0.46m coal, the Bath Lodge Coal. 23m below the Bath Lodge Coal, and separated from it by alternating shales and sandstones, lie the Splint Coal, 0.9m of poor coal and coaly shale, and 2.5m lower the evocatively named Hawk's Nest Coal, 1m thick. The latter two coals cropped out on the foreshore west of Bath Lodge and though worked out there, fragments can be found by digging at low-water. All three coals were worked from adits in the cliff south of Bath Lodge and from a shaft sited near the houses at Carrig-uisnagh. This shaft was drained by water power - the pumps fed by a race from the Carey River, a full kilometre away, the course of which can still be followed across the golf links. This area was known as the Salt Pans Colliery. At a variable depth below the Upper Coal Group - usually a few metres - lies the uppermost fossiliferous marine horizon, McGildowney's Marine Band. This group reaches its maximum and quite unusual development in the Bath Lodge area, where it is split into two leaves by the lenticular Pans Rock Sandstone which reaches a thickness of 16m and thins in a distance of about 300m to only 0.5m. The upper leaf, seen on the foreshore below the footbridge to the Pans Rock, is 3m thick including a 1m band of sandy crinoidal limestone. The lower leaf, seen on the foreshore east of the last cottages (which include the remains of the last of the salt pans from which the area gets its name) is just over 2m thick of fossiliferous shales. This marine horizon can be followed for 3km to the east and appears in many of the faulted blocks which will be described later. At the White Mine, south of Port Watty, where massive pale sandstones were quarried in the cliffs, the dark shales of the Marine Band are seen at the top of the cliff. An inclined mine, now filled in, was driven southward from the back of the quarry to the Main Coal. The sandstones between the Marine Band and the coal are about 40m thick, with a couple of shale partings and the Main Coal, about 1.4m thick, and the Wee Coal about 0.3m, and about 4m below it, were the principal coals worked in the district. At the White Mine the Main was about 20m below sea level, and the problems of working with a waterlogged and friable sandstone roof proved insurmountable, even when tried in the early 1950's with powerful electric pumps. At Doon, the bluff above the coast road, a few metres beyond the side road to Corrymela, shows the marine band at road level, below a massive sandstone. The dark shales with veins of gypsum and abundant fossils are the most accessible exposure of the McGildowney's band. The overlying Hawk's Nest and Splint Coals were worked from shallow pits above the bluff here. Passing eastward from Doon we enter the North Star Colliery, one of the largest unfaulted blocks in the western part of the coalfield. The 60m throw of the western boundary fault here brings the Main Coal from below sea level to the level of the cliff top where it is concealed by glacial drift. Here, however, the beds below the coal appear in cliff and foreshore. The mainly sandstone succession includes two thin coals, the Wee Coal, a short distance below the Main, and the Middle Till, about half way down the sandstone succession, which is about 20m thick. Both are poor quality coals and coaly shales, but the old miners pursued them assiduously and they are rarely seen at outcrop. The sandstones pass down into grey fossiliferous shales with thin ribs of limestone, about 8m in all, overlying the Main Limestone. The limestone is hard, crinoidal, and notable for large productids; it occurs in two leaves separated by a band of fossiliferous shale about 0.2m thick. The total thickness of limestone is 1.7m to 2.2m. It crops out locally in the grass-covered cliff south of the road and is best seen when its southerly dip brings it down to the foreshore near the conspicuous North Star dyke, where it is seen to be underlain by 5m of grey shale and then by pyritous sandstone with coal streaks. The latter represents the Limestone Coal, which is locally better developed but never reaches workable thickness. Beside the dyke at road level is the North Star mine, still open with a stone-built entrance, which acted as a drainage level as well as a coal haulage adit for the whole of the block, some 25 hectares. Driven with a slight rise to the south to allow drainage and easier movement of laden tubs (wagons) the overlying Main and Wee coals were dropped into the tubs through inclined 'shoots' or 'troughs' from the pillar and stall workings. The Main Coal must have originally cropped out on the grassy slope but has long been worked out to outcrop. A small mine opened to `rob the pillars' in the 1950's showed the Main Coal to be a bright coal 1.4m thick. About 200m east of the small coal-yard known, erroneously, as `Marconi's Cottage' the Main Coal was worked among the group of small faults margining the North Star mine by several small mines at about road level, and in the following Goldnamuck Colliery it was worked by horizon mining - like North Star - by a sea-level adit now obscured but marked on old plans. The Main Limestone, here at about the level of the road, is completely obscured by spoil tips and slips, but the massive sandstones on the foreshore are the group below the limestone. For about a kilometre both the Main Limestone and the Main Coal are covered by slips and spoil, though the massive sandstones in the cliffs can be recognised as those above, between and below these beds. For much of this traverse the cliffs are capped by the Gobb Sill, about 20m thick; which was intruded into the shales below the Hawk's Nest Coal. The impressive cliffs below the sill show mainly massive sandstones, but intermediate softer beds are seen as breaks in the succession and sometimes as outcrops at Casnatinny, the spur at the east end. The section seen here is (from the top): Massive sandstone 9m, McGildowney's Marine Band (shale, ironstone thin coal) 5m, Massive sandstone 30m, Main Coal position 3m, Sandstone 8m, Middle Till 1m, Sandstone 14m, Calcareous shales 9m, Main Limestone 2.5m, Shales 4m, Sandstones 25m, Coaly fireclay 2m, Red sandstone 12m, Coal and fireclay (Sronbane Coal) 1m, Sandstone, red 9m+, totalling 134m. The Main Coal in this area was worked from the `Gobb Grand Level', driven south from just above High Water. Like most of the other coastal mines the coal was worked up-dip towards the cliff outcrop and dropped down shoots to tubs in the bottom level. Such plans as exist delineate a system of airways with names such as Paugh's Arch and Capehorn. Just east of Casnatinny a fault with a downthrow of about 30m to the east drops the succession and the Main Coal was worked here from adits in the cliff and a drainage level in Portnagree which still discharges just above HWM. 150m east from the Portnagree fault another dislocation with a downthrow of 55m to the west brings in a group of beds, seen in excavations at the foot of the cliff and in the waterfall at Carrickmore - the Carrickmore Marine Band, about 14m of calcareous shales, thin limestones, thin coals and a bed of blackband ironstone. The ironstone, up to 0.75m thick, is mainly siderite (iron carbonate) with a proportion of bright coal as thin streaks. It was worked as an iron ore in the mid-nineteenth century from adits north and east of the waterfall. The ironstone and associated thin coals were calcined on hearths near the mine and the calcined ore shipped to Scotland from a wharf on the Carrickmore Islands. The extensive flat terrace on the shore was built from waste from the hearths and the mine, and fragments of raw and calcined ore can be found on the beach. Below the Carrickmore Marine Band another 100m+ of sandstones form the cliffs east of the waterfall, passing down into the series of poor coals, shales, volcanic tuffs and mudstones seen around the base of Fair Head. Structure: The total thickness of Carboniferous rocks in north Antrim may be as much as 700m, but the coastal productive coalfield is only about half this and the area described here from Bath Lodge to Carrickmore, about 250m. The Carboniferous sedimentary rocks were deposited in an embayment in the Dalradian North Antrim ridge, and in the southern part of the area dip northwards, off the ridge. Subsequent movement, probably in Hercynian times, has formed a shallow east-west basin and the higher beds seen on the coast dip south or south-east at shallow angles. The north-east trend of the coastline and the occurrence of a series of NNE-trending faults, generally down-throwing to the west, tends to raise the level of individual beds to the east, but the same beds tend to be repeated along the coastal exposures from Bath Lodge to Gobb. As far as the productive coalfield is concerned the limiting factor to the south is the Great Gaw (fault) which runs east-west from Bath Lodge and effectively limits the extension to the south of the succession here described. The course of this limiting fault can be determined at Bath Lodge where it throws the highest beds against Lavas of Carboniferous age, a throw of about 400m, and in the North Star mine where the main level passed from the productive coal-bearing beds into an unknown barren succession after cutting a fault about 400m south of the coast. A similar intersection was recorded at Portnagree, 2km to the east. Palaeontology: Within the succession described in this report the shales above the Carrickmore Marine Band have yielded a marine fauna with polyzoa and a restricted shelly fauna including Lingula sp., Othotetids, Productids, Nuculids and Pectinids. The Main Limestone and the calcareous shales above and below it have an abundant marine fauna of which the most useful species is Productus (Gigantoproductus) giganteus J. Sowerby ss., which is restricted to the uppermost Vis‚an in Scotland. The shales below the Main Coal yielded a single Lingula. McGildowney's Marine Band which can be followed from the Pans Rock to Gobb contains a characteristic marine fauna, including Archaeocidaris spines, Camarotoechia sp., Productus (productus) sp., Streblopteria ornata and Sulcatopinna sp. The only fossil of stratigraphic significance from this horizon is the Orthotetid brachiopod Schellwienella rotundata, the type of which came from Tirfergus Glen in Kintyre, some 35km from Ballycastle. This brachiopod is regarded in Scotland as diagnostic of the lower part of the Namurian. The sequence between the Main Limestone and McGildowney's Marine Band is very much condensed compared with the Scottish succession and there is no indication of the dividing line between Vis‚an (P) and Namurian (E), so the boundary has been taken, somewhat arbitrarily, at the base of the Main Coal. Igneous rocks: (Carboniferous Lavas) It is known from borehole evidence that about 300m below the lowest rocks described on the coastal traverse at Carrickmore, the Carboniferous succession includes a group of contemporaneous basaltic lavas about 40m thick. These are seen in part at the surface in Murlough Bay and in the Carey River, but the best exposures are in the cliffs south of Bath Lodge, to the south of the gully which marks the line of the Great Gaw. In the cliffs and the escarpment which runs south across the golf course it is possible to differentiate probably six separate lava flows, none more than 9m thick, mainly of basalts closely comparable with Carboniferous lavas from the Midland Valley of Scotland. Igneous Rocks: (Tertiary Intrusive) Like all areas around the Antrim Basalt Plateau intrusive rocks are common here. The largest in the area is the Fair Head Sill, about 90m thick and cropping out over an area of over 2.5km2. Like the other sills and dykes in the area it is an olivine- dolerite. The Gobb Sill is part of the same intrusive complex but is only 20m thick and crops out over about 0.5km2. The most notable of the several dykes seen in the coastal sections is the North Star, 5m wide with well-marked longitudinal joints. This intrusion, also of olivine-dolerite, shows a fine-grained marginal selvage about 0.15m wide on both sides against the local calcareous shales, though the latter show little or no sign of alteration at the contact. The Carrickmore Dyke, seen on the foreshore, appears to be part of a fault intrusion which includes the Carrickmore Islands. The dyke is 2m to 5m wide with a veneer of highly indurated shales on its western face. Both dyke and shales dip at 80 deg. to the west and are seen on the foreshore for about 45m, but no sign of such a dyke is seen on the line of the fault in the cliff nor on the island, only 25m to the north. The intense induration of the country rock, for up to 5m, is not seen at any of the other dykes in the area. The main island, a stack about 50m x 25m, is mainly made up of intensely hornsfelsed shale, near horizontal and with intruded bands and veins of dolerite. The central zone, however, is an irregular pipe of coarse dolerite with numerous wisps, slabs and blocks of hornfels, the whole giving the impression of turbulence. The two smaller offshore islands appear to be mainly of hornfels. This complex may have been in some way a feeder to the Fair Head and Gobb Sills. | |
| Importance: | |
The coastal exposures are a prime teaching area for students from school to university level. Though unlikely to be a national resource in the future, as all the economically workable coal has been extracted, further study may well reveal more about the depositional features in a small marginal coalfield. | |
| Interpretation: | |
The fossil evidence indicates the correlation of this coalfield with that of Macrihanish, 40km to the north-east, and the Carboniferous succession of the Midland Valley of Scotland, rather than to the succession in the rest of Ireland. The Ballycastle beds include the lowest part of the Namurian and the upper part of the Vis‚an. | |
| Conclusions: | |
The preservation of the foreshore and cliff exposures from Bath Lodge eastwards is of first importance as a unique study area for lower Namurian and upper Vis‚an strata. | |
| Notes: | |
For information on other sites in Subarea-9 see Key Site 1182 - Subarea-9; Ballycastle. | |
| Keywords | |
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| Rocks: | Coal, Lava, Limestone, Sand, Sandstone |
| Fossil Groups: | Brachiopod, Crinoid |
| Fossil List: | Lingula sp. , Productus giganteus J. Sowerby, Schellwienella rotundata, Streblopteria ornata |
| Access | |
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| Management: | |
1 - The foreshore exposures are probably safe from development pressures, as the exposed nature of the coast precludes the construction of marinas or other recreational features. 2 - Further development of holiday cottages and caravan sites on the terrace should be discouraged. 3 - Exposures are so extensive and subject to tidal renewal by wave action that pressure from student sampling is negligible. 4 - To maintain the integrity of the cliff exposures, development within 100m of the cliff-top should be discouraged. | |
| Uses | |
| Uses: | The narrow raised-beach terrace below the cliffs, partly covered by scree, landslip and mine spoil, has a few dwellings and a small caravan park on it. Evidence of earlier mining and quarrying is ubiquitous. Beyond the cliff top the land is mainly rough grazing with a golf course at the western end. |
| Educ. Level: | Secondary / Advanced level / Undergraduate |
| References (6) | |||
|---|---|---|---|
| Griffith, R., 1829. Geological and Mining Surveys of the Coal Districts of the Counties of Tyrone and Antrim., Dublin. | |||
| Hamilton, W., 1786. Letters concerning the Northern Coast of County Antrim., London. | |||
| Kelly, J., 1868. On the Geology of the County of Antrim, with parts of the adjacent Counties. Proceedings of the Royal Irish Academy, vol. 10, pp.49-97. | |||
| Symes, R.G. & Wilkinson, S.B., 1886. Explanatory memoir to accompany sheet 44. Memoirs of the Geological Survey of Ireland, pp.1-44. | |||
| Wilson, H.E. & Robbie, J.A., 1966. Geology of the country around Ballycastle. Memoirs of the Geological Survey Northern Ireland. | |||
| Wright, W.B., 1924. The Geology of the Ballycastle Coalfield. Memoirs of the Geological Survey of Ireland. | |||
| Map(s): | See the 1:50,000 O.S. Sheet 5 (Ballycastle). | ||
| Record type: | Environment Serv. GIS, ESCR report | ||
| Entered by: | Crowther, P.R. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Ballycastle Coalfield, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=19. Accessed on 2026-11-05. |
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