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Earth Science Conservation Review
| Greenisland - site of local interest | Antrim |
| Site number: | 732 | ||
| Locality Type: | Coastal section | Status: | local interest |
| Grid Reference: | J374843,J388856 End(s) of linear site | ||
| Google maps: | 54.68845,-5.86929 | ||
| County: | Antrim | Council area: | Antrim & Newtownabbey Borough Council |
| Period: | Quaternary, Tertiary, Triassic | ||
| Stages: | Holocene, Lower Triassic, Middle Triassic, Palaeogene, Upper Triassic | ||
| Lithostrat: | Mercia Mudstone Group, Sherwood Sandstone Group, Upper Estuarine Clay, Greenisland Sill | ||
| Site Description | |
|---|---|
| Highlights: | |
This section along the northern foreshore of Belfast Lough, between Loughshore Park and Green Island, contains exposure through the Triassic sediments of northeast Ireland. The section exposes strata belonging to both the Sherwood Sandstone Group and the Mercia Mudstone Group. Locally these are intruded by the Greenisland Sill and a complex swarm of dyke-like bodies. Additionally, an exposure of the Estuarine Clays (Holocene) can be seen along this stretch of coast. | |
| Description: | |
The Sherwood Sandstone Group (Lower Triassic) has a very extensive outcrop in the Belfast Lough area but it is mainly under the waters of the lough. Only along the coast [J374 843] just north of Loughshore Park can an exposure of this Group be seen on the northern shore of the lough between Whiteabbey and Whitehead. The beds are dominantly red fine-grained sandstone although there are some yellow or grey bands and occasional red and green mudstone. Although the overall dip of the succession is to the northwest, numerous gentle open folds occur in the foreshore sections. Northeast along the foreshore, exposures of the Mercia Mudstone Group (Middle to Upper Triassic) can be seen. The rocks consist largely of fine-grained sediments, usually mudstones but with some siltstones and silty mudstones. The predominant colour is red-brown but grey, green and chocolate coloured beds occur, and greenish reduction spots are not uncommon. Folding, predominantly along NNW-SSE axes can be observed in the section here. These open folds range in amplitude from a few metres up to 200m and plunge mostly to the northwest at low angles. Along the Mercia Mudstone Group foreshore exposure, a complex swarm of basaltic dyke-like intrusions (Palaeogene) stands out from the sea-washed mudstones. The dykes are frequently sinuous and bifurcate, have cross-connections with one another and occur as a series of en-echelon bodies, though possibly connected at depth. Sill-like cross connections are also developed and are well exposed. At Raven Hill [J388 852] an exposure of the Greenisland Sill can be seen where intrusion breccias are developed in both the dolerite intrusion and in the Triassic mudstone wall-rock. Finally, one of the few exposures of the Estuarine Clays (Holocene) is seen on the foreshore southwest of Green Island at [J385 852]. Mc Millan (1947) described a 0.33m thick Thracis Clay (Upper Estuarine Clay) overlain by a 0.13m thick Old Zostera Bed (Recent). Mc Millan obtained 58 species of mollusca from the clays of which five had not previously been reported. | |
| Importance: | |
The site is of limited scientific value though it does preserve one of the few exposures of the Sherwood Sandstone Group and the Estuarine Clays on the northern foreshore of Belfast Lough. The site is of significant educational value as it exposes a section through the gently folded Triassic sediments of the area as well as a complex series of Palaeogene intrusions. As such it would make an ideal locality to learn about past environments and geological mapping techniques. | |
| Notes: | |
The section lies along a section of a heavily used and well established walking route along the northern foreshore of Belfast Lough. | |
| Keywords | |
|---|---|
| Rocks: | Basalt, Clay, Dolerite, Mudstone, Sandstone, Siltstone |
| Fossil Groups: | Mollusca |
| Structures: | dyke, sill, open folds |
| Access | |
|---|---|
| Approach: | Coastal exposure between Loughshore Park and Green Island. |
| Uses | |
| Educ. Level: | The site is of significant educational value. |
| Record type: | SLNCI Report | ||
| Entered by: | E M Porter | ||
| Last updated: | 09/10/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Greenisland - site of local interest, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=732. Accessed on 2026-11-06. |
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