Kilkeel Steps
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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: Carboniferous, Cretaceous, Quaternary, Silurian · Rock Type: Granite, Limestone
Landscape processes: Coastal, Glacial, Periglacial, Volcanic / Igneous
Description
Kilkeel Steps Pleistocene The area is of special scientific interest because of its important geology. The site contains important cliff exposures of late glacial sediments that record ice marginal deposition in a marine basin that now forms the Moume Plain. These sediments also contain evidence of fluctuating sea levels in the form of raised beach deposits and older infilled troughs separating mesas of diamict. The sediments of the Moume Plain were deposited approximately 20,000 years ago as the ice sheet that covered much of Ireland was beginning to break up. At this stage, the ice mass had separated into three distinct units. These three ice masses formed the margins to the depositional basin. It was sediment derived from the ice and it's interaction with marine water that controlled the sequence found at Kilkeel. Three flat topped or mesa-like structures separated by troughs are exposed at the site. The mesas are composed of horizontal, massive sandy beds of diamict with variable texture. Rock clast composition is primarily of Silurian country rock with some Carboniferous material, both of local provenance and indicating a Carlingford Lough source area. Occasionally, fine grained massive diamict containing Scottish Ailsa Craig granite, Cretaceous limestone clasts and marine shell fragments, is exposed beneath the main mesa deposits, indicating transport by ice coming from the north. The diamict is thought to have formed between 21,000 and 19,000 years ago. The troughs separating the mesas are filled with marine deposited horizontal sand and mud with isolated cobbles and contain abundant microscopic foraminifera tests throughout, notably Elphidiurn clavaturn, that allow accurate dating of the trough fill to approximately 19,100 years ago. At the junction between the mesas and trough, interbedded diamict, sand and gravel and silt are found to be inclined toward the trough centre, their structure indicating deposition from turbidity flows. The top of the entire sequence is truncated by more recent sand to cobble grade raised beach deposits. With the onset of ice retreat, the diamict that composes the mesa structures was deposited from a combination of ice rafted debris, rain out and resedimentation. More coarse material was introduced from efflux and turbid gravity flows from the ice margins. A fall in relative sea level exposed the diamict to sub aerial erosion, during which time the trough structures were formed. It is possible however that the troughs were formed in a subaqueous environment; such formation may be related to initial erosional action of the turbidity currents. If the troughs do represent a subaerial erosional phase, then clearly a low relative marine stand would be necessary to expose the diamict. This would then be followed by a marine transgression, the latter associated with the infilling phase. The marine low stand appears to be isostatically controlled while the latter appears to be a local record of a regional-global event. This sequence is capped by late glacial beach deposits. This raised beach extends from Kilkeel to Cranfield Point. It truncates the older mesa and infill deposits and is associated with a fossil cliff notch at +19m OD. The presence in this beach of features associated with periglacial conditions implies a late glacial age. Isostatic readjustment following full ice retreat has exposed these important glaciomarine sediments; it is estimated the coastline has seen a net uplift of some 160-170 metres. https://www.daera-ni.gov.uk/publications/kilkeel-steps-assi