Coolcran

Also within

Fermanagh County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Rock Outcrop · Geological Period: Carboniferous, Devonian · Rock Type: Conglomerate, Mudstone, Sandstone

Landscape processes: Fluvial, Volcanic / Igneous

Description

Coolcran Carboniferous Stratigraphy The area is of special scientific interest because of its important geology, which is found at outcrop in a stream section approximately 2km south of Broughe~. Mountain. The rocks exposed are of Carboniferous age, some 320 million years old. The outcrop consists of interbedded sandstone, mudstone and conglomerates of the Coolcran Conglomerate Member from the Topped Mountain Sandstone Formation. Coolcran is the stratotype locality for the Coolcran Conglomerate Member and the site also contains miospore fossil plant remains bearing mudstone. The beds exposed dip between 20°_28° to the north west. The base of the member is a 3m thick conglomerate bed containing blocks of volcanic lava up to 0.12m diameter. This is succeeded by 30m of massive to flaggy, medium to coarse-grained grey-red sandstones with thin layers of pebbles and conglomerates up to 1m thick. Fossil plant pollen, miospores, have been recovered from 0.07m of green micaceous mudstone, interbedded with the conglomerates and sandstones, in the lowest part of the Coolcran Conglomerate Member. The miospores recorded are indicative of a late Visean age of the Carboniferous late Asbian-Brigantian stages. The assemblage of species include Calamospora parva, Densosporites sp. D. anulatus, Discernisporites sp., Granulatisporites granulatus, Knoxisporites stephanephorus Leiotriletes adnatus, Lycospora pusilla, Raistrickia sp. Retusotriletes sp. and Vallatisporites ciliaris. Rocks of the Kilskeery Group were originally deposited as sediment in a subsiding, non marine sedimentary basin. There is evidence that two basins developed at the same time, separated by a topographic high composed of metamorphic and Lower Palaeozoic sedimentary rocks. The Coolcran Conglomerate Member, exposed in the stream section at Coolcran, was deposited in the southern of these two basins. Increased uplift during the early Brigantian Stage of the Carboniferous led to increased erosion of the central high, producing alluvial fans that prograded south depositing the coarse grained-pebbly sandstones, conglomerates and mudstones of the Topped Mountain Formation. The Kilskeery Group was originally thought to be of Devonian age, part of the Lower Old Red Sandstone Fintona Group. Sites such as Coolcran have yielded plant material which allowed the age of the rocks to be accurately determined as younger than first thought and belonging to the Carboniferous period. https://www.daera-ni.gov.uk/publications/coolcran-assi

Plant communities