Church Bay
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Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Geological Feature: Raised Beach · Geological Period: Quaternary · Rock Type: Chalk
Landscape processes: Coastal, Glacial, Karst
Description
Church Bay Sea level history The Church Bay area is of national importance in understanding the sea level history of Northern Ireland and the North Channel area. It is composed of a chalk gravel bar that now sits several metres above present sea level. The gravel bar records previous sea level during the Late Pleistocene and also more recently, during the Holocene. Fossil shells found in the gravel have allowed dating of the feature to the Late Midlandian Stage of the last Ice Age. Evidence suggests that a series of smaller ridges oblique to the main gravel feature are recurves on a spit. It is the only gravel ridge feature of its type in Ireland. The site is to the east of Church Bay village and to the west of a scarp line located approximately 600m from the current coast line, between Mill Bay to the south and the harbour to the north. It forms a shore parallel ridge that diverges to form a second ridge extending landward at its northern end. The ridge reaches a maximum height of 10 metres above sea level. A former pit exposure showed the ridge to be composed of well rounded chalk gravel beds, typically clast supported, dipping east at 25-28°. Samples of the common periwinkle Littorina littorea taken from the ridge have enabled Carbon-14 dating of the feature to 12,335 +/-80 years old, placing it within the Woodgrange interstadial, a time of warmer conditions between colder conditions in the Late Midlandian. The dated ridge then provides indicative evidence of sea level at this time. The barrier feature has been interpreted as a spit that extended from south to north, this on the basis of the curving of the feature landward at its distal northern end. Beach material was derived from chalk cliffs to the south which are no longer present, although reworked glacial material may also have contributed. The feature eventually extended to enclose two former coastal lagoons on raised beach deposits that are now the low lying ground to the east of the ridge. Morphology of the barrier indicates two phases of deposition. The lower level gravels are finer grained and are interpreted as being deposited at mid beach level as the feature extended north. The upper gravels are coarser and are dominated by disc shaped clasts that suggests over washing of the spit crest during an aggradation phase. This indicates aggradation of over 3 metres, suggesting either deposition under rising sea level or the raising of the gravel crest by wave action. This morphological evidence demonstrates that former sea-levels must have been several metres above the current level. A relative high sea-level stand during the Holocene post 10,000 years BP led to raised beach material being reworked, resulting in a lower series of ridges being formed. This relationship between raised beach forms linked to two former relative sea-levels high is extremely unusual. https://www.daera-ni.gov.uk/publications/church-bay-assi
Species mentioned
Show the 1 species mentioned in the description, with red-list status| English name search for this in other sites |
Latin name search with Google |
IUCN / Red List | Type | Family |
|---|---|---|---|---|
| periwinkle | Littorina littorea | LC | mollusc | littorinidae |