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Earth Science Conservation Review
| Carnlough Coastal Peat and Raised Beach Ridges | Antrim |
| Site number: | 1141 | ||
| ESCC: | IS | ||
| Locality Type: | Coastal section | Status: | ESCR |
| Grid Reference: | D287171 Approximate | ||
| Google maps: | 54.9852,-5.98952 | ||
| County: | Antrim | Council area: | Mid & East Antrim Borough Council |
| Period: | Quaternary | ||
| Stages: | Holocene, Pleistocene | ||
| Site Description | |
|---|---|
| Highlights: | |
Beds of peat, infrequently exposed on the beach at Carnlough, are known from radiocarbon dating and pollen analysis to be of Late Glacial and early Holocene age. The peats overlie beach gravels below which is a thick sequence of finely laminated silts and clays, and glacial till. Inland of the beach are two shore- parallel, raised gravel ridges that are probably younger than the peats. The sedimentary sequence preserved at Carnlough records evidence for coastal and landscape changes from c. 15,000 to 6,000 years BP. | |
| Introduction: | |
Carnlough Bay is a broad embayment at the foot of Glencloy on the east coast of Co. Antrim. In 1975 erosion of beach sand from the inter-tidal area revealed two peat beds, one of which contained large fragments of wood, separated by a thin sandy silt horizon. The peat outcrop was only 10m wide but extended 300m alongshore. The distribution of the peat, its contained pollen and age, and the characteristics of the underlying sediments were investigated by D.B. Prior, S.M. Holland and M.M. Cruickshank. Their findings were published in 1981 (Prior et al., 1981). | |
| Description: | |
Seven horizons were identified by Prior et al. (1981) from coring the foreshore at Carnlough. These were as follows: 1 - Upper peat: 20-30cm thickness, dark brown, compact and well humified. Contains abundant wood fragments identified as Salix. 2 - Blue-grey sandy silt: variable thickness (max. 20cm), sometimes absent; containing angular and sub-angular basalt fragments sorted into crude stone nets which could be seen where this layer was exposed by erosion of the upper peat. Grain size of matrix 10% clay, 20% silt, 70% sand. Possible solifluction layer. 3 - Lower peat: 15-25cm thickness, black, compact and well- humified. 4 - Lower sandy silt: variable thickness (max. 10cm) and discontinuous. Very variable texture: grain size analysis, 10-12% clay, 22-37% silt, 15-68% sand. 5 - Sand with thin clays: 40-45cm thickness; predominantly sand with occasional thin, discontinuous clay partings. 6 - Blue sticky clay: very thin (1-5cm), unctuous and plastic; found on the landward part of the foreshore section. 7 - Beach gravel: 200-300cm thickness; highly rounded chalk and basalt pebbles in a sandy matrix. In addition, coring revealed that the beach gravels cover a thick sequence (c. 8m) of finely laminated silts and clays. Below these laminated deposits, hard light brown till containing basalt and chalk fragments was observed. Four radiocarbon dates were obtained on samples of peat and wood. The wood fragment came from the surface of the upper peat. The dates were as follows: UB-984 Surface of upper peat 8,110+/-125 UB-985 Middle of lower peat 11,740+/-170 UB-986 Outcrop of lower peat 11,630+/-140 UB-987 Wood from surface of upper peat 8,175+/-95 Pollen analysis was also conducted on the peat layers. The lower peat has a low ratio of arboreal (tree) to non-arboreal pollen, and a high percentage of Juniperus. In the upper peat, the ratio of arboreal to non-arboreal pollen increases. Salix, Betula and Pinus are present at first; the arrival of Corylus marks a dramatic rise in the proportion of tree pollen and sees the decline of Juniperus, Gramineae and Empetrum. | |
| Importance: | |
The Carnlough site is of international (Irish) importance as it is one of very few coastal sites that apparently retains evidence for a sequence of coastal and landscape changes spanning the period from wastage of the last ice sheet (c. 15,000-13,000 years BP) to the mid-Holocene marine transgression (c. 6,000 years BP). As such it includes organic materials that accumulated during the Late Glacial (Woodgrange) Interstadial. | |
| Interpretation: | |
The pollen spectrum of the lower peat, particularly the presence of Juniperus and absence of tree pollen, together with radiocarbon dates of c. 11,700 and 11,600 years BP, suggest that organic accumulation took place in the Late Glacial (Woodgrange) Interstadial. Prior to this episode several distinctly different depositional periods occurred. The thick laminated silts and clays overlying the till may represent fluvioglacial deposition during deglaciation. Their characteristics suggest deposition in a locally ponded water body. Later, but before peat accumulation, beach gravels were deposited and record a marine transgression. Horizons 4-6 were also deposited prior to peat formation. Their origin is by no means clear although a phase of solifluction has been suggested. Prior et al. (1981) recognised that their investigations of all materials below the lower peat were of a preliminary nature and their conclusions somewhat tentative and speculative. Above the lower peat, the blue-grey sandy silt with crude stone nets is suggestive of frost-related processes and given its stratigraphic position is most likely of Late Glacial (Nahanagan) Stadial age (c. 11,000-10,000 years BP). The upper peat probably began forming in the early Holocene and records climatic amelioration, landsurface stability and vegetation colonisation following the cold climate conditions of the Late Glacial Stadial. The radiocarbon dates from this peat of c. 8,100 years BP have been used by Carter (1982) to constrain the position of his Holocene sea level curve. Clearly the maximum relative height of the Holocene transgression is younger than these dates. The stratigraphic relationship of the upper peat to the two shore-parallel, raised gravel ridges has not been determined. If the peat continues under them they can be assigned to the mid- Holocene transgression. Whereas peat on the beach has probably suffered some erosion and cannot provide a precise age for the trangression, peat located beneath the gravel ridges may give a much closer estimate for the timing of this event on the east coast of Northern Ireland. | |
| Conclusions: | |
The Carnlough sediment sequence appears to provide a record of coastal and landscape changes spanning the period 15,000-6,000 years BP. The sequence contains evidence for dissolution of the last ice sheet, a possible Late Glacial marine transgression, organic sedimentation in the Late Glacial (Woodgrange) Interstadial, disturbed ground conditions in the Late Glacial (Nahanagan) Stadial, organic sedimentation in the early Holocene, and the mid-Holocene marine transgression. Although some of the conclusions regarding the sequence are tentative and speculative, due to limited investigations, the site is undoubtedly of significant scientific interest in the context of Late Glacial and Holocene environmental change. | |
| Notes: | |
The paper by Prior et al. (1981) stresses the preliminary nature of the investigations. Given the importance of the site it is essential that this work is extended to provide a full and detailed record of the sedimentary sequence. To this end a programme of coring through the raised gravel ridges and at beach level would provide detailed stratigraphic data and further samples for analyses. Note: all age estimates used in this report are in uncalibrated radiocarbon years Before Present (BP). | |
| Keywords | |
|---|---|
| Fossil Groups: | Plant |
| Relations: | Late-glacial deposit, Marine deposit |
| Geomorph: | beach ridge, buried peat, gravel beach, pollen analysis, radiocarbon dating, raised beach gravel |
| Measurements | |||||
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| Length: | 300 m | Width: | 10 m | Height: | |
| Depth: | Area: | ||||
| Access | |
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| Management: | |
There is no known management of the site. Because of its location (on the beach), the sedimentary sequence is usually buried by sand and is protected from operations/activities that are likely to pose a threat to the maintenance of its scientific interest. |
| References (2) | |||
|---|---|---|---|
| Carter, R.W.G., 1982. Sea-level changes in Northern Ireland. Proceedings of the Geologists Association of London, vol. 93, pp.7-23. | |||
| Prior, D.B., Holland, S.M. & Cruickshank, M.M., 1981. A preliminary report on the late Devensian and early Flandrian deposits on the coast at Carnlough, County Antrim. Irish Geography, vol. 14, pp.75-84. | |||
| Map(s): | See the 1:50,000 O.S. Sheet 9 (Ballymena, Larne). | ||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Last updated: | 8 Jan 2005 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Carnlough Coastal Peat and Raised Beach Ridges, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1141. Accessed on 2026-11-06. |
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