Culnafay
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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.
Peat habitats store centuries of carbon and depend on a stable, waterlogged water table. Warmer, drier summers dry out peat, making it far more vulnerable to wildfire and to carbon release — a pressure that can undo years of restoration work regardless of how well the site is otherwise managed.
Geology & landscape
Geological Period: Quaternary · Rock Type: Glacial Till
Landscape processes: Glacial, Peatland / Mire
Description
Culnafay Holocene peat and related stratigraphy The area is of special scientific interest because of its deposits of diatomite. Diatomite consists of accumulated diatom frustules with differing amounts of clay, silt, sand and peat. Diatoms are microscopic aquatic plants, surrounded by a silica box, or frustule, of various shapes, depending on the species. The diatomite also known as Kieselguhr or Bann clay deposits in Northern Ireland were one of the most extensive freshwater diatomite sequences of post-glacial age in the world. The deposits were mainly formed between 7500 and 5000 before present BP, and are found in low lying land around the northern shore of Lough Neagh and in the Lower Bann valley. Although diatomite was formed in water and represents the extent of a former, larger Lough Neagh, the presence in the deposits of archaeological remains shows that these marginal areas were only seasonally inundated. At Culnafay, as in much of the Bann valley, the diatomite was probably deposited in an elongated lake, as indicated by its essentially linear form. The dominance of benthic bottom dwelling species of diatom in the lowest records marks the former presence of a shallow water body, but this was probably isolated from the main lough. The change to deeper water conditions is reflected by the increased presence of planktonic free floating species at higher levels. Basal deposits are of early Atlantic age post 7500 years BP, but the upper sequence has been truncated by erosion. The diatomite record also contains Mesolithic occupation sites and it is one of the key locations for the Irish Mesolithic-Middle Stone Age-chronology. It also shows the lateral transition from diatomite to glacial till, marking the former shoreline. This is the last large deposit of good quality diatomite remaining in this area. Its natural topography indicates how the landscape might have appeared during the time of formation. The diatomite is of international importance for biological, geological, hydrological and climatological reasons. Its archaeological significance is also considerable, given its contemporaneous links with sites of early human settlement. This assemblage gives a record of past water levels in the Lough Neagh basin, and of climatic change since the last period of Irish ice. These remaining sites are amongst the most important deposits of freshwater diatomite in the world, and are unique when considered with the associated materials. https://www.daera-ni.gov.uk/publications/culnafay-assi