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Lurgan River, Mullylusty TownlandFermanagh
Lurgan River, Mullylusty Townland, Co. Fermanagh, showing contact between Glenade Sanfstone Formation (the fallmaker and main face) and Meenymore Formation (below overhang at base of face)..
Summary Full report
Site Type: Stream section
Site Status: PASSI
District: Fermanagh District Council
Grid Reference: H087413
Rocks
Rock Age: Carboniferous (Asbian, Visean)
Rock Name: Glenade Sandstone Formation, Meenymore Formation
Rock Type: Limestone, Mudstone
Interest
Fossil Groups: Goniatite
Other interest: No data, No Data

Summary of site:

The succession of Carboniferous rocks in County Fermanagh is complex, reflecting rapidly changing conditions in the environments that produced them. To keep track of events, good exposures are essential, though not always available. This account describes the rocks of the Meenymore Formation, generally poorly exposed but here in the banks and bed of the Lurgan River on the south side of the Belmore Mountain uplands, all but a few metres of the entire formation can be seen.

Although the actual line of contact of the Meenymore with the formation below, the top member of the Dartry Limestone Formation, the Carn Limestone, can not be seen, its typical shales are clearly exposed. The first Meenymore rocks, no more than a few metres above the base, are thin limestones with films of lime-fixing alg' (primitive, simple plants) and unfossiliferous mudstones jointed into blocks. Curiosities here are oil-filled cavities in the rock. 17 m of rock are exposed above these beds with two prominent sandstones forming waterfalls, the upper one succeeded by 6 m of mudstones with thin limestones. 9.5 m of sandstones and thin mudstones follow further upstream. At the northern end of the section the top beds of the Meenymore, around 75 cm of laminated algal limestones similar to those at the base, come into sharp contact with the contrasting orange-stained pebbly conglomerate forming the base of the succeeding Glenade Sandstone. Fortunately there are fossils present near the base of the Meenymore, goniatites (extinct relatives of the octopuses and squids that inhabited coiled shells) which give a diagnostic age, in the Asbian stage of the Lower Carboniferous, about 336 million years ago. The rocks and their sedimentary structures indicate a coastal interface between sediment-laden fresh water conditions and the marine intertidal zone. Neither dominated and the evidence for periodic emergence and drying of sediment can be seen in the form of desiccation cracks in the mudstones, limestones and sandstones. Even the shells of dead goniatites were reworked in the agitated shallows and colonised by coatings of lime-fixing alg'. The rocks were formed on the shores of the supercontinent of Laurentia as it drifted imperceptibly northwards across the equator. This is an important section because 44 m of strata, out of the total thickness of 48 m of the Meenymore Formation, can be seen and for this reason it should be protected from any development that could pollute the river or obscure the rocks in its bed and banks.


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