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Earth Science Conservation Review
| Carrickfergus Castle - site of local interest | Antrim |
| Site number: | 708 | ||
| Locality Type: | Foreshore | Status: | local interest |
| Grid Reference: | J414873 Centroid | ||
| Google maps: | 54.71428,-5.80586 | ||
| County: | Antrim | Council area: | Mid & East Antrim Borough Council |
| Period: | Tertiary, Triassic | ||
| Lithostrat: | Mercia Mudstone Group | ||
| Site Description | |
|---|---|
| Highlights: | |
The massive intrusion upon which Carrickfergus Castle was built appears to be a local thickening of a dyke, perhaps associated with a fault. On the foreshore beneath the castle are excellent examples of the local country rock (Mercia Mudstone Group) which has been affected by contact metamorphism. | |
| Description: | |
On the foreshore just northeast of Carrickfergus Castle there are exposures of the Mercia Mudstone Group (Triassic). Although the Mercia Mudstone Group consists largely of fine-grained sediments, usually mudstones but with some siltstones and silty-mudstones, sandy bands (or skerries) are known to occur and the sandstone beds seen here represent one of these units. The massive dolerite intrusion (Fergus’s Rock) on which Carrickfergus Castle is built appears to be a local thickening of a dyke, perhaps associated with a fault. On the foreshore immediately below the castle the contact between the Mercia Mudstone Group and the dolerite intrusion can be examined and the hornfelsed nature of the mudstone is obvious. It is worth pointing out that although the castle itself is built of basalt, the architraves and corner stones are made of Magnesian Limestone (Permian) the closest outcrop of which occurs on the southern side of Belfast Lough at Cultra. | |
| Notes: | |
The intrusion upon which the castle is built is known historically as Fergus’s Rock (from the Irish Carraig Fheargeas) after a 6th century warrior who drowned off the coast here on his return from Scotland. The Norman castle was built around 1180 by John de Courcy and during the medieval period was the centre of English influence in Ulster. It is now in the care of the Environment and Heritage Service (DOE NI). The site is one of Northern Ireland’s most popular visitor attractions and is an internationally recognised image of the region. | |
| Keywords | |
|---|---|
| Rocks: | Dolerite, Hornfels, Mudstone, Sandstone |
| Structures: | dyke |
| Uses | |
|---|---|
| Educ. Level: | The site is of significant educational value. Examples of sedimentary, igneous and metamorphic rocks can all be examined at the one locality. |
| Record type: | SLNCI Report | ||
| Entered by: | E M Porter | ||
| Last updated: | 09/10/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Carrickfergus Castle - site of local interest, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=708. Accessed on 2026-11-06. |
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