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Earth Science Conservation Review
| Carrickarade | Antrim |
| Site number: | 63 | File Number: | D04 |
| ESCC: | EC | ||
| Locality Type: | Coastal section | Status: | ASSI |
| Grid Reference: | D062450 Centroid | ||
| Google maps: | 55.24101,-6.3304 | ||
| County: | Antrim | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Tertiary | ||
| Stages: | Eocene, Palaeocene | ||
| Lithostrat: | Antrim Lava Group, Lower Basalt Formation, Tholeiitic Middle Basalt Member | ||
| Site Description | |
|---|---|
| Highlights: | |
Occurrence of section through volcanic neck with exposures of agglomerate and tuffs and associated intrusive basaltic masses. | |
| Introduction: | |
The island of Carrickarade with its rope bridge connection to the mainland represents a section through an explosive volcano which is unique in its extent in the whole of the Tertiary igneous province of northeast Ireland. The volcanic remains consist of exposures of agglomerate comprising fragments of basalt, Chalk and Lias clay ejected during the initial explosive phase of the Antrim lavas. This activity was probably phreatomagmatic caused by the gradual upward movement of magma into water-saturated sediments. The occurrence of Tertiary vents in north Antrim has been reviewed by Patterson (1963) and the geology of the Carrickarade volcano is dealt with in detail in Wilson and Manning (1978). | |
| Description: | |
Present exposures show the vent to extend for approximately 600 m from Larry Bane Bay in the west to Portaneevy in the east, with an approximately similar north-south extent in the vicinity of Carrickarade Island. The details of the geology are shown in the geological map and cross-section in Wilson and Manning (1978). The vent margins are visible to the west at Casnageeragh. The vent consists of agglomerate made up of blocks of basalt up to 3 m in diameter embedded in a matrix of volcanic ash with occasional fragments of Lias clay and Chalk. Carious weathering on parts of the agglomerate outcrop suggests a derivation from finely comminuted limestone. The agglomerate is intruded by a number of veins and irregular masses of dolerite which appear to be part of a later phase of the eruptive history when magmatism had largely replaced explosive activity. The cliffs on the east side of Carrickarade Island and the higher ground at Binard on the mainland are formed of this later dolerite. This dolerite forms the sea cliffs to the east; towards Portaneevy there is a near vertical contact between the vent and the chalk, with both agglomerate and dolerite occurring, although the actual margin is obscured by scree deposits. A possible Lower Basalt flow rests on the Chalk south of Portaneevy. The western margin can be seen to the west of the small island of Stackahorlin where it rises steeply in the lower part of the cliff before flattening out to the west and overlying the Chalk at the cliff top. Above the Chalk at Portaneevy is a layer of chalky tuff 25 m thick overlain by lavas of the Lower Basalts and Causeway Tholeiites. The pale-grey chalky tuff extends westward across the vent margin and along the face of the scarp towards Ballintoy where it reaches a maximum thickness of 60 m, forming a flat ash-core. | |
| Importance: | |
The Carrickarade vent is unique within the Tertiary volcanic province of northeast Ireland in the extent of the exposure across and through a major explosive volcano. It is the largest and most important of the series of vents exposed in north Antrim and is an important feature in the interpretation of the earliest stages of Tertiary volcanic activity in the region. Within the Tertiary provinces of the British Isles the Carrickarade tuffs and agglomerates allow comparison with basal tuffs exposed beneath the plateau basalts of Mull and Skye. | |
| Interpretation: | |
The initial phase of eruption in Antrim featured explosive activity, primarily seen in a series of vents exposed in north Antrim. Preston (1982) has suggested that these events were probably phreatomagmatic and a consequence of magma moving into water-saturated sediments at shallow depths, probably as sill intrusions. The vent at Carrickarade represents this initial phase producing the agglomerate vent infilling containing blocks of basalt, Chalk and Lias clay. Later magmatic events formed the intrusive dolerite masses such as those seen at Carrickarade Island and at Binard on the mainland. Some of these intrusive masses may have reached the surface thus explaining the conjectured Lower Basalt flow resting on the Chalk to the south of Portaneevy (Wilson & Manning, 1978). The chalky tuff exposed between the Chalk and the overlying basalt successions probably erupted from a source other than the Carrickarade vent since its maximum thickness is seen near Ballintoy, a kilometre west of Carrickarade. This suggests its source was a vent in the area of Larry Bane Bay, of which the basaltic islands off Larry Bane Head may be vent intrusions (Wilson and Manning, 1978). | |
| Conclusions: | |
The site offers excellent exposures through the largest explosive vent formed during the initial and probably phreatomagmatic phase of eruption of the Antrim basalts. | |
| Notes: | |
The area of the volcanic vent lies almost entirely within that maintained by the National Trust, and also within the Causeway Coast AONB designated by the Department of the Environment. The site is a popular tourist attraction particularly during the summer months when the rope bridge is in place. Cliffs around the bridge on the mainland side are dangerous and inaccessible and the access path is currently fenced to restrict access to the cliff edges. On Carrickarade Island the outcrop is less dangerous but is freely accessible and there is potential for members of the public to fall. The access path from the NT carpark passes the disused dolerite quarry at Knocksoghy and the disused Chalk quarries at Larry Bane Head. | |
| Keywords | |
|---|---|
| Rocks: | Agglomerate, Dolerite, Tuff |
| Structures: | tuff, volcanic vent |
| Relations: | Intrusion |
| NonGeol: | Sheep grazing. Tourist attraction; Area of Outstan |
| Measurements | |||||
|---|---|---|---|---|---|
| Length: | Width: | 600 m | Height: | ||
| Depth: | Area: | ||||
| Access | |
|---|---|
| Approach: | Management of the site is by the National Trust with carpark and toilet facilities near Ballintoy, some 1.5 km from the rope bridge, with access via a rough footpath along the cliff top. Access to Carrickarade Island is via the rope bridge which is in place from approximately April to October each year. |
| Restrictions: | The exposures are predominantly coastal cliff and foreshore and are generally inaccessible. |
| Management: | |
Management of the site is by the National Trust, with carpark and toilet facilities some 1.5 km from the rope bridge. | |
| Threats: | Since the main exposures are in general inaccessible there is little pressure on the locality from geological sampling. |
| References (2) | |||
|---|---|---|---|
| Patterson, E.M., 1963. Tertiary vents in the northern part of the Antrim plateau. Quarterly Journal of the Geological Society of London, vol. 119, pp.419-443. | |||
| Wilson, H.E. & 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. | |||
| Map(s): | For site location see the 1:50,000 O.S. Sheet 5 (Ballycastle). | ||
| Record type: | Environment Serv. GIS, ESCR report, J. Preston l | ||
| Entered by: | Hamilton, M.J. | ||
| Last updated: | 8 Jan 2005 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Carrickarade, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=63. Accessed on 2026-11-06. |
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