Larkhill
Also within
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: Rock Outcrop · Geological Period: Precambrian
Landscape processes: Coastal, Volcanic / Igneous
Birds & fish recorded
Fish
| Species | Season |
|---|---|
| Atlantic salmon | Unknown |
Description
Larkhill Precambrian, Mineralogy The area is of special scientific interest because of its' important geology.The rocks exposed here are Precambrian in age. Evidence suggests these rocks represent the pre Dalradian basement in Northern Ireland. The rocks host important exposures of feldspar rich pegmatites, which were once quarried in the Larkhill area as a raw material for the Belleek Pottery. The main rock series exposed is from the Slishwood Division of the Lough Derg Group that extends from west Fermanagh almost to the Atlantic coast of Donegal. The rocks are psammites and semi pelites that have undergone at least two metamorphic events; pre-Caledonian possibly Grenvillian high pressure, high temperature granulite facies metamorphism followed by a later, low-grade amphibolite facies metamorphic event Dalradian. Despite the altered nature of the rocks, some of the original sedimentary structures can still be observed. Pegmatite veins are ubiquitous throughout the outcrop of the Lough Derg Group. Wherever they are seen, pegmatites post-date almost all other lithological and structural boundaries in this series. The pegmatite veining is associated with late stage igneous activity, the veins representing selective fractions of mineral rich fluids injected into the pre-existing rock. The most distinctive feature of the pegmatites are the large interlocking crystals of pale pink and salmon coloured alkali feldspar mainly microcline. This alkali feldspar is intergrown with varying amounts of grey and off-white quartz, plagioclase feldspar, biotite and muscovite mica. Quartz occurs in the pegmatite both as late stage, cross-cutting veins and as intimate graphic intergrowths within the feldspar. The mineral composition of the Larkhill pegmatite is broadly comparable with pegmatites elsewhere in the vicinity as calculated from chemical analyses. Alkali feldspar varies from 60% to 80% of the total rock composition with 10% to 20% sodic feldspar albite, and 10% to 30% other constituent minerals including quartz and mica. https://www.daera-ni.gov.uk/publications/larkhill-assi