Earth Science Conservation Review

Summary Full report
Site number:1145  
Locality Type:Cliff, Coastal section Status: ESCR
Grid Reference: D045445,D120413 End(s) of linear site, Not Entered
County: AntrimCouncil area:Causeway Coast & Glens Borough Council
Period:Quaternary, Tertiary, Cretaceous
Stages:Eocene, Holocene, Palaeocene, Santonian
Lithostrat:Antrim Lava Group, Ulster White Limestone Formation
Site Description
This site has fine examples of contemporary and raised rock coast landforms including cliffs, caves, arches and sea stacks, eroded primarily in chalk but also in basalt. Raised beach features are especially well developed just west of Ballintoy Harbour. These include a fault-guided chalk cliff fronted by a raised beach terrace, and sea stacks cut into basalt slump blocks. Large mid-Holocene landslips can also be seen on the chalk cliffs to the east. Further east at Carrick-a-Rede marine erosion has exposed a section through the best example of a volcanic vent in Northern Ireland.
The coast between White Park Bay on the west and Ballycastle on the east comprises a suite of coastal landforms cut in Lower Cretaceous chalk and Tertiary basalt. The western section around Ballintoy is notable for its well developed raised shoreline, primarily cut in chalk. The morphology here is complex due to the interplay of faulting, RSL changes, contemporary marine processes and man's activities. To the east the Carrick-a-Rede volcanic vent interrupts the chalk cliffs. From there to Ballycastle the steep cliffs are cut in chalk and basalt, although along some stretches, only the basalt is above sea level.
No detailed academic work has been carried out on the landforms of this site. The only specifically geomorphological descriptions are contained in general studies by Carter and Bartlett (1988), and Carter (1991). Carter (1990) described the Boheeshane Bay landslips. Elsewhere there are incidental references to the coastal landforms in geological publications. Some of these are very general, e.g. Charlesworth (1953); however more detailed accounts are given in Geological Survey Memoirs by Wilson and Robbie (1966) and Wilson and Manning (1978). The former describe the cliffs and foreshore immediately west of Ballycastle, while the latter deal with the area between White Park Bay and Carrick-a-Rede.
The coast on this site trends WNW-ESE and is essentially rocky. From Ballintoy Harbour west to Whitepark Bay the shoreline consists of a cliff in the local metamorphosed chalk, fronted by a terrace. On the seaward side of the latter there are a number of islands, stacks and enormous blocks consisting of basalt, and less commonly, chalk. These lie on and within the intertidal platform. Some have been eroded by the sea into natural arches, or are pierced by caves. An igneous intrusion, the Bendoo Plug, forms the headland beside the old Coastguard Station on the cliff top at Ballintoy.
The coast east of Ballintoy Harbour demonstrates a series of embayments and headlands, including Boheeshane Bay and Larry Bane Bay. These are northward opening crenellate bays backed by impressive vertical cliffs cut into near horizontal chalk strata. Boheeshane Bay is notable for its spectacular slope failures where large blocks of the cliff face have slumped downwards. Further east the cliffs of Larry Bane Bay are cut by two dykes. At the foot of the cliffs there is a jumble of rockfall slabs. Rockfall has revealed cavities where embryonic speleoforms can be seen. Landward of these chalk cliffs a flat terrace at about 50m O.D. extends well inland to, and beyond, Ballintoy village.
The chalk cliffs of Larry Bane Bay terminate against the tuff cliffs of the Carrick-a-Rede volcanic vent which interrupts the chalk for over 0.5km alongshore. Here marine erosion has exposed a section through the neck of an old volcano which is quite unique in Northern Ireland. The rope bridge across the dissected vent is a well known tourist attraction. The west face of the island and also the shore of the mainland directly opposite are formed of basaltic tuff. Cliffs of massive dolerite form the eastern side of the island, and also form the mainland cliffs a short distance east of the rope bridge. Near the vent a thick bed of grey ash in the cliffs forms a marked visual contrast with the black basalt.
The cliffed coastline between Carrick-a-Rede and Ballycastle is largely unknown and inaccessible. The coast is steep and rocky with virtually no significant accumulations of beach material except in Portkinbane, the re-entrant immediately to the west of Kinbane Head, where there is a storm beach of basalt cobbles fronted by a narrow chalk platform. The basic structure is that chalk and basalt form respectively the lower and upper sections of the cliff faces, although faulting produces a good deal of local variation. The chalk is not always present, as it is below sea level, along some stretches. Thus basalt forms the entire cliff face from Port Campbell to Port Calliagh, and also forms the cliffs immediately landward of Ballycastle Harbour. Along most of the remainder of the coast both lithologies are present. The cliffs also contain subsidiary beds of tuff and laterite. There are a few short sections where igneous intrusions form the cliffs, e.g. at Gobe Feagh, east of Carrick-a-Rede, a dolerite intrusion forms the promontory, while further south-east the Portnakillew intrusion interrupts the chalk cliffs to form a subdued headland.
There is a waterfall behind Leg-na-Sassenach at Kinbane where a stream flows off the edge of the basalt plateau. A fine example of a chalk sea-arch penetrates Kinbane Head, just seaward of the ruined castle. There are many caves in both basalt and chalk along the coastal stretch between Portnakillew, south-east of Kinbane, and Castle Point near Ballycastle. Just south-east of Portnakillew the raised cliffs delineate a wooded amphitheatre opening to the sea. Here Lias grey shales can be seen in a small exposure among slip debris just above high water mark.
In the chalk at Castle Point, just below the Giant's Parlour, there is a raised beach cave about 35m long. Further east, from Portnagree to Ballycastle Harbour, basalts form the whole cliff and foreshore, including the cliffs behind the harbour, the Granny Rock sea-stack and the rocks exposed at the boat slip. The basalt was formerly extensively quarried in the area now occupied by houses and the harbour car park.
This site provides a fine illustration of the range of hard rock landforms which result from the interaction of geology, RSL changes, slope processes and marine erosion. The Ballintoy area to the west offers some of the best examples of raised coastal landforms in the region. The Carrick-a-Rede vent is unique in Northern Ireland, while the chalk/basalt coast to the east provides interesting illustrations of the interaction of chalk and basalt with marine processes.
The entire area has a high scenic value and as Ballintoy is readily accessible by vehicles, it already attracts many visitors. Perhaps surprisingly, past quarrying activities do not detract from its scenic quality. Most of the coast from Ballintoy Harbour to Carrick-a-Rede is owned by the National Trust who have a small visitor reception centre and a carpark at the disused Larry Bane quarry. A path gives access to Carrick-a-Rede running along the top of the Larry Bane cliffs. Boheeshane Bay is somewhat less accessible, but the cliff-top can be reached on foot from the Larry Bane car park. However, the northerly aspect of both bays does not allow optimum views of the cliffs themselves. The coast from Carrick-a-Rede to Ballycastle is largely inaccessible, although pedestrian access is possible at Kinbane Castle and at Ballycastle Harbour.
Interpretation of the Ballintoy area in particular is complicated by the interplay of complex RSL fluctuations, and the activities of man. Remnants, and occasionally longer stretches, of a raised rock platform can be traced along much of the Ballintoy- Ballycastle cliffline. However, great caution is required when identifying planation surfaces on jointed lithologies like chalk and basalt. This is especially the case with basalt because of its characteristic trap featuring. Wilson and Robbie (1966) state that the platform averages c. 4-5m above mean high water. It is probably the shoreline associated with the maximum Post-glacial RSL estimated by Carter (1982) to have attained approximately 2-4m above present, c. 5500 to 6500 yr BP.
The coast around Ballintoy has been extensively remodelled by man in the recent historical past. This is especially true at Larrybane and, less so, at Ballintoy Harbour, where large-scale quarrying of the metamorphosed chalk cliffs for lime was an important activity in the 19th and early 20th centuries. Quarrying activities created scarps and terraces and even "beaches" which are difficult to distinguish from naturally occurring features. The coastline is dominantly fault-controlled, particularly to the immediate west of Ballintoy Harbour. Here the coast coincides with a major geological lineament, the Port Braddan fault, the line of which runs approximately east-west through the harbour and across the bay to the west. The cliffs of the backshore exemplify primary structural control as they consist in part of a fault-line scarp in the massive chalk. Along the fault the basalt has been downfaulted relative to the chalk, often resulting in an apparent reversal of the usual elevational relationship of these two rock types.
Charlesworth (1953) has described this area immediately west of Ballintoy Harbour as a classic example of fault-drag, i.e. the curling down of the rocks into the fault on the upthrow side and their curling up on the downthrow side. The chalk south of Ballintoy Harbour is roughly horizontal, but is tilted at an increasing angle towards the north until it is almost vertical. The basalt on the north or down-throw side is similarly dragged up towards the fault so that the columnar lavas between the harbour and White Park Bay are canted over to the north in the conical raised-beach sea-stacks.
Many of the caves and crevasses are eroded along small cross faults and joints leaving an intricate pattern of small scale coastal scenery. The rocky bedrock outcrops, and old quarrying spoil heaps, are a source of fragments which have abraded into rounded pebbles and infilled some of the re-entrants with small bay-head beaches. These pebbles are exploited and a small industry has grown up supplying local builders. However the supply of pebbles is limited and at the current rate of exploitation the pebbles will soon be exhausted.
The slope failures in Boheeshane Bay have been caused by marine erosion at an earlier, somewhat higher, RSL undercutting the near-horizontal chalk beds along their bedding planes enabling large blocks - up to 5,000m3 - to topple seaward. The date of these is unknown, certainly none are of recent origin. It seems likely that these blocks would have started to collapse in the period c. 5500 to 6500 yr BP as the sea level fell away from its Holocene maximum. At that time wave activity would have been insufficient to remove the debris. There is no evidence of major instabilities today, although the block faces are scarred by minor rock falls and earth slips.
At Larry Bane Bay Wilson and Manning (1978) identified remnants of a platform and associated caves about 6m O.D. cut in the chalk. They also state that in the vicinity of Bendoo Plug and Ballintoy Harbour there are a number of these caves in chalk, all appearing to be related to the 6m level. It is probable that this stand of RSL corresponds with the Mid-Holocene maximum described by Carter (1982). Wilson and Manning (1978) view the flat terrace landward of the cliffs as a pre-glacial marine feature, cut in the soft tuff bed which underlies the lava succession in this district.
Beyond Ballintoy the coastal processes become affected increasingly by the presence of Rathlin Island. The Moyle Strait (Rathlin Sound) between the island and the mainland serves to concentrate tidal energy and alter incoming wave patterns. The tidal curve for Ballintoy is somewhat unusual with a strong double or over-tide, often causing two high waters within a few hours. The second high water moves in time and amplitude relative to the primary high water.
The geomorphological interest of the Carrick-a-Rede vent is its role in illustrating the effect on coastal planform of differential erosion of various lithologies. The vent is filled with a coarse tuff agglomerate, and a dolerite intrusion. The latter is extremely resistant to erosion, and has been able to withstand wave attack to stand proud of the slowly retreating cliffline. It now forms the Carrick-a-Rede island as the softer tuff to the south has been broken through by wave action.
The Carrick-a-Rede to Ballycastle coastal stretch appears to experience little change. The lack of any large accumulation of beach material suggests that, on the broad scale, the coast experiences limited erosion. However the finer detail of the coast is largely the result of differential marine erosion along joints and faults in the chalk and basalt. This erosion is aided by the small tidal range, 1.2m at Ballycastle, which concentrates wave energy in a narrow vertical band. In a few places, e.g. the foreshore and headland at Kinbane Head, the chalk is completely shattered and recrystallised. Coastal re-entrants do not necessarily form at these points, because, as Wilson and Robbie (1966) point out, the altered chalk on this coast is virtually as hard as the normal chalk of Northern Ireland. Differential erosion around highly resistant igneous intrusions does, however, account for the promontory of Gobe Feagh, and the subdued headland at Portnakillew.
South of Castle Point, the chalk demonstrates massive beds with large vertical and near vertical joints which, on the raised beach platform and on the foreshore, have been eroded to give sharp gullies and rock pools. Here the long raised beach cave at the Giant's Parlour has been cut along a major joint in the chalk. Given that the chalk is carbonate, chemical processes of erosion may also play a part, although their effects are often masked by mechanical erosion. An example of chemical erosion can be seen east of Carrick-a-Rede in Port More where a projecting chalk spur has weathered into a series of roughly conical pinnacles, probably from intense attack by sea spray.
Seaward of the basalt cliff backing Ballycastle Harbour the Granny Rock is a basalt raised beach stack on the raised rock platform. This platform, in basalt and chalk, is well preserved at this location, although the eastern extremity is now covered by the harbour car park.
The Ballintoy/Ballycastle coastal section, and particularly its western end, contains the best raised coastal scenery in chalk in Northern Ireland. The Carrick-a-Rede volcanic vent is unique in the region. The scenic value of the entire coastal stretch is high, and the western section is readily accessible.

There is a general lack of research on rock coasts, both from geomorphological and ecological perspectives. The Ballintoy area with its varied lithologies (basalt, chalk, tuff, dolerite), and morphologies (sub-horizontal cliff tops, sub-vertical cliff faces, offshore reefs and islets, sea-stacks, raised beach terraces), would be an ideal site for these investigations, and would complement the existing body of work on its geology. The detailed mechanisms and geomorphological/ecological influence of the double or over-tide also needs investigation.

Rocks:Basalt, Dolerite, Limestone, Tuff
Relations:Coastal processes
Geomorph:arch, cave, cliff, raised shoreline, shore platform, stack
Management:The cliffs, largely in chalk, appear very stable although there are occasional small scale rockfalls. While the coast in general is rock, and much of the shoreline is largely inaccessible, the scenic harbour at Ballintoy acts as a 'honey-pot' attraction and draws substantial numbers of visitors in summer. This may lead to a problem in the future if visitor numbers continue to rise, as the narrow winding access road already becomes a bottle-neck at busy times. On the cliff tops and terraces to the west of the harbour heavy grazing may have detrimental effects on the flora, but no data are available to confirm this. East of Ballintoy the National Trust manages the recently upgraded facilities associated with its Larrybane and Carrick-a-Rede properties. These are accessed via a roadway just east of Ballintoy village.
Threats:Over-grazing on cliff tops; high density of visitors, especially in summer.
Carter, R. W. G. 1990: Ballintoy - Boheeshane Bay. In Field Guide No. 13. North Antrim and Londonderry. Irish Association for Quaternary Studies, Dublin
Carter, R. W. G. 1991: Shifting Sands: A Study of the coast of Northern Ireland from Magilligan to Larne. Her Majesty's Stationery Office, Belfast
Carter, R. W. G. and Bartlett, D. 1988: Coast erosion and management in the Antrim Coast and Glens and the Causeway Coast Areas of Outstanding Natural Beauty. In Final Report of the Coast Erosion Survey. Department of Environment (Northern Ireland)
Charlesworth, J. K. 1953: The Geology of Ireland. Oliver and Boyd, Edinburgh and London
Wilson, H. E. and Manning, P. I. 1978: Geology of the Causeway coast. Memoir for one-inch geological sheet 7. Memoirs of the Geological Survey Northern Ireland, HMSO, Belfast
Wilson, H. E. and Robbie, J. A. 1966: Geology of the country around Ballycastle. Memoirs of the Geological Survey Northern Ireland,
Map(s): See the 1:50,000 O.S. Sheet 5 (Ballycastle).
Rec Type ESCR report    
Enterer: E M Porter
Updates: 27 Apr 2003 / 14 FEB 97 / 11 FEB 97
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