| Previous Site | Next Site |
Earth Science Conservation Review
| Portrush West Strand Coastal Peat | Antrim |
| Site number: | 1142 | ||
| ESCC: | IS | ||
| Locality Type: | Coastal section | Status: | ASSI |
| Grid Reference: | C855402 Approximate | ||
| Google maps: | 55.20192,-6.65716 | ||
| County: | Antrim | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Quaternary | ||
| Stages: | Holocene | ||
| Site Description | |
|---|---|
| Highlights: | |
A bed of peat containing large fragments of wood, including the stumps and trunks of trees, is infrequently exposed on the West Strand beach at Portrush. Radiocarbon dates indicate the peat to be of early to mid-Holocene age. These dates, along with the stratigraphy of sections logged in the 1930s, demonstrate that the peat pre-dates the maximum relative height of the Holocene transgression. Few details of the sub-peat stratigraphy are available but aeolian dune sands and another peat bed have been recorded. All these materials suggest the site has undergone a complex Holocene evolution. | |
| Introduction: | |
The West Strand at Portrush, Co. Antrim, is an arcuate sand beach c. 1km in length. Prior to the construction of a sea wall and promenade in the 1960s, the beach was backed by a sand cliff in which a conspicuous bed of peat was present. This peat was noted by Symes et al. (1888) and Coffey & Praeger (1904), but it was Erdtman (1928) who first reported (briefly) on the contained pollen. However, the most detailed work on the pollen and plant macro-fossils is that of Jessen (1949) who also described and offered an explanation for the various sand units exposed below and above the peat. More recently, Wilson & Manning (1978) reported details of the exposures as logged in a re-survey of the area in 1957 by the Geological Survey, and provided stratigraphic information obtained from a borehole put down at beach level in 1938, three years after Jessen's last visit to the site. The first radiocarbon dates from samples of the peat were reported by Wilson & Carter (1990). | |
| Description: | |
The sand cliff exposure documented by Jessen (1949) was destroyed by the construction of sea defences in the 1960s and all that remains of the materials he described are infrequent exposures of peat on the beach when sand has been stripped by storm waves. However, the importance of the peat bed is best appreciated when placed in its true stratigraphic context. The section described by Jessen extended for 550m from just north of Castle Erin to just south of the stream that enters the sea near the southern end of the strand. Jessen identified four main stratigraphic units from the surface downwards as follows: 1. Light-grey blown sand, several metres thick (inland from the cliff this layer is built up into dunes, some of which are over 15m above sea-level). 2. Reddish-yellow laminated beach-sand without shells. Along most of this section scattered stones were seen at the top of the layer only, but at the south-western end they occurred throughout it. The stones were rounded beach-pebbles up to 25cm in diameter, and their occurrence in the top of the sand indicates the upper limit of the raised beach. 3. Peat which was exposed under the raised beach at five different places in the cliff. 4. Sand without stones or shells lay beneath the peat. This lower sand was considerably finer in grain than either the beach sand or the upper blown sand in the cliff. Because of its form, rising into two low ridges, it may be considered to be blown sand. What lay beneath this deposit was not determined. More detailed descriptions of the peat from four locations along the cliff face were provided by Jessen as well as three pollen diagrams. These descriptions reveal changes from highly humified fen peat into Phragmites peat containing abundant plant macro- fossils, especially wood of Alnus and Betula. Wilson & Manning (1978) give additional details of the sand cliff stratigraphy but, more importantly, report on the stratigraphy of a borehole put down at beach level to the north of Castle Erin in 1938. This borehole started in what Jessen considered to be the lower aeolian dune sand and recorded another layer of peat, 0.4m thick, 4.5m below the beach. This was underlain in turn by 3m of sand, 1.8m of boulders and sandy clay, and 2.1m of grey sand before reaching boulder clay. At least in the area north of Castle Erin, therefore, two peat layers occur. No pollen or plant macro-fossil data or radiocarbon dates are available for the lower peat. In 1988, re-culverting work on the stream that enters the sea towards the southern end of the strand provided temporary exposures in the upper peat and overlying beach sand immediately east of the railway embankment. At least 1.37m of peat was exposed but the base was not seen. Samples from the top and bottom of the observed peat thickness were radiocarbon dated to 5,920+/-80 years BP (Beta-36943) and 7,310+/-100 years BP (Beta-36944) respectively (Wilson & Carter, 1990). | |
| Importance: | |
The West Strand sediments are of international (Irish) importance as they appear to contain a record of coastal changes (including marine transgression and regression) from early to late in the Holocene, and are one of the few sites to possess such a long record. The lower dune sands described by Jessen are of potential international (Irish/British) importance as they could represent some of the earliest known Holocene dunes in these islands. | |
| Interpretation: | |
The interpretation offered by Jessen for the stratigraphy he observed remains unchallenged and is given below. 1. During the early Holocene (or even earlier) low sand dunes developed at the site. 2. As sea level began to rise and restrict drainage, water- logging occurred between the dunes encouraging peat formation. From the radiocarbon dates it is now known that peat initiation pre-dates 7,300 years BP. As peat formation proceeded in the inter-dune hollows the low dune slopes and crests were gradually covered by soligeneous peat. 3. At the maximum of the transgression, sea level rose above the surface of the peat and deposited the beach sand. From the radiocarbon dates the maximum relative height of the Holocene transgression is placed at c. 5,900 years BP. 4. During and after the subsequent fall in relative sea level, aeolian sands were deposited on top of the beach sands. A more complex pattern of coastal changes would undoubtedly be provided by analysis and interpretation of the borehole sediments and stratigraphy reported by Wilson & Manning (1978). | |
| Conclusions: | |
Sediments at Portrush West Strand provide evidence for a complex pattern of coastal changes spanning most of the Holocene. Early Holocene (or earlier) peat and aeolian sands are overlain by peat that began developing prior to 7,300 years BP. Peat growth was terminated by deposition of beach sands associated with the Holocene marine transgression c. 5,900 years BP. The beach sands are overlain in turn by aeolian dunes. | |
| Notes: | |
It would be useful to have more information about Jessen's lower dunes; if his interpretation of these sands is correct then they would be the earliest Holocene dunes in Ireland and possibly the British Isles. More information is also needed about the 0.4m thick peat bed and the 3m thick sand unit below this peat identified in a borehole put down at beach level to the north of Castle Erin in 1938 (Wilson & Manning, 1978). Only when these materials have been rigorously investigated will the full scientific value of Portrush West Strand to Holocene coastal evolution be known. A series of cores along the West Strand is required to obtain this information. Note: all age estimates used in this report are in uncalibrated radiocarbon years Before Present (BP). | |
| Keywords | |
|---|---|
| Fossil Groups: | Plant |
| Geomorph: | beach sand, buried peat, pollen analysis, radiocarbon dating, sand dune |
| Access | |
|---|---|
| Management: | |
There is no management of this site. Because of its location (on the beach) the peat is more often that not buried by sand and thus protected from operations/activities that are likely to pose a threat to the maintenance of its scientific interest. | |
| Uses | |
| Uses: | Recreation. |
| References (6) | |||
|---|---|---|---|
| Coffey, G. & Praeger, R.L., 1904. The Antrim raised beach: a contribution to the Neolithic history of the north of Ireland. Proceedings of the Royal Irish Academy, vol. 25C, pp.143-200. | |||
| Erdtman, G., 1928. Studies in the Postarctic history of the forests of north-western Europe. 1 Investigations in the British Isles. Geologiska Foreningens Forhandlingar, vol. 50, pp.123-192. | |||
| Jessen, K., 1949. Studies in Late Quaternary deposits and floral history of Ireland. Proceedings of the Royal Irish Academy, vol. 52B, pp.85-290. | |||
| Symes, R.G., Egan, F.W. & McHenry, A., 1888. Explanatory Memoir to accompany Sheets 7 and 8. Memoirs of the Geological Survey of Ireland. | |||
| 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. | |||
| Wilson, P. & Carter, R.W.G., 1990. Portrush - Mill Strand. In Field Guide No. 13. North Antrim and Londonderry., pp.35-39 Irish Association for Quaternary Studies, Dublin. | |||
| Map(s): | See the 1:50,000 O.S. Sheet 4 (Coleraine). | ||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Portrush West Strand Coastal Peat, County Antrim, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=1142. Accessed on 2026-11-08. |
| Previous Site | Next Site |