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Earth Science Conservation Review
| Roddan's Port - site of local interest | Down |
| Site number: | 749 | ||
| Locality Type: | Coastal section | Status: | ASSI |
| Grid Reference: | J641658 Centroid | ||
| Google maps: | 54.51445,-5.466 | ||
| County: | Down | Council area: | Ards & North Down Borough Council |
| Period: | Quaternary | ||
| Stages: | Holocene, Late Glacial | ||
| Site Description | |
|---|---|
| Highlights: | |
The clay and peat deposits at Roddan’s Port were laid down during two major episodes of marine submergence, one during the early Late Glacial period and the other in the mid-Holocene period. The earlier transgression is represented by a red marine clay which had a widespread occurrence on the County Down coast while the later transgression is represented by the local development of a post-glacial raised beach. Analysis of pollen, macroscopic plant remains, shells, ostracods and algae have allowed a reconstruction of the site and have permitted limited correlations. | |
| Description: | |
The general setting is the well-developed drumlin landscape that was left behind following the decay of the last ice in County Down. The drumlins vary in height and rise above the lakes and marshy ground that separate them. Some of this marshy ground lies around the 7-8m contour in the Ards area and was submerged during two phases of marine transgression in the Late Glacial and Holocene periods. Following retreat of the Late Glacial sea, a freshwater, or possibly at first a slightly brackish, lake remained. An unbroken succession of typical and clearly developed Late Glacial and Holocene sediments accumulated in this basin. This was abruptly ended when a grey lagoon clay, marking the second marine transgression, buried the fen communities. Subsequently the whole deposit was buried by inland movement of a beach bar, which helped compress the underlying deposits. Eventually continuing isostatic recovery raised all the deposits above the reach of the sea. Since then, further sea level readjustment has involved the erosion of these raised beaches and wave attack at Roddan’s Port has led to the re-exposure of the greater part of the formerly buried lake deposits. | |
| Importance: | |
Due to active erosion along the eastern coastline of County Down, opportunities for recovering dateable and pollen-bearing deposits between the two major marine transgressions have been reduced. Roddan’s Port is therefore of exceptional importance for detailing the history of the northeast coastline of Ireland. | |
| Interpretation: | |
The Late Glacial deposits have a 2m thick red clay at their base which is interpreted as having been deposited in a late-Glacial sea when the land was beginning to recover, following the withdrawal and decay of ice from the coastal lands. The overlying deposits of grey solifluxion layers represent Lower and Upper Dryas clays of Pollen Zones I and III with an intervening organic layer formed during the mild Allerød interstadial period of Pollen Zone II. Samples from the base of Pollen Zone II have yielded a radiocarbon age of 11,845 ± 150 years BP. The overlying Holocene sequence consists of thin layers of mud, peat, clay and silt, and raised beach boulders and sand. Pollen analysis of the Phragmites peat indicates it was deposited at the base of Pollen Zone IV and has yielded a radiocarbon age of 10,130 ± 170 years BP. | |
| Notes: | |
The site falls within the Outer Ards pASSI / pSPA. See also ESCR Key Site 5 - Roddan's Port. | |
| Keywords | |
|---|---|
| Rocks: | Clay, Gravel, Sand |
| Structures: | late-glacial sequence, post-glacial pollen zone |
| Relations: | Beach deposit, Lacustrine sediments, Late-glacial deposit, Marine deposit |
| Geomorph: | raised beach, peat |
| Paleoenv: | glacial, post-glacial |
| Access | |
|---|---|
| Approach: | This site is located on the eastern coast of the Ards peninsula 3km south of Ballywalter. |
| Uses | |
| Educ. Level: | This site is of limited educational significance. |
| Record type: | SLNCI Report | ||
| Entered by: | E M Porter | ||
| Last updated: | 09/10/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Roddan's Port - site of local interest, County Down, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=749. Accessed on 2026-11-08. |
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