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Marlbank-Cuilcagh Mountain Region; Western MarlbankFermanagh
Summary Full report
Site Type: Karst
Site Status:
District: Fermanagh District Council
Grid Reference: H1034
Rock Age: Quaternary, Carboniferous (Asbian, Holocene, Visean)
Rock Name: Cloghan Hill Limestone Member, Dartry Limestone Formation, Glenade Sandstone Formation, Glencar Limestone Formation, Knockmore Limestone Member, Meenymore Formation
Rock Type: Dolerite, Limestone, Sand, Sandstone, Shale
Minerals: Calcite
Other interest: bedding, dyke, fault, joints, rift, No Data, cave, clastic sediments, dendritic river cave, doline, drift, dry valley, karren, limestone pavement, sinkhole, speleothem

Summary of site:

This small wedge of land between the western edge of the Marble Arch System catchment (Key Site 1156) and the border with the Republic of Ireland contains three small catchments, one entirely in Northern Ireland and two crossing the border to resurge there.

The major cave sites in the area are Hammer Pot, Hanging Rock Risings, Pollnasalac, Polltullyard, and Legacapple and there are a number of lesser sites include Revolution Pot, Dave’s Hole, Tullynakeeragh Gravel Lake, Killykeeghan Pots, Marlbank Rising and Gortaree Sink. All of these speleological features are described separately under their own names on this website. Cave exploration is in its infancy in this area and at the time the full report was updated in 1997, over 750m of cave, in total, had been explored. The three catchments are the Shannon Pot System, the Ture Rising and the Hanging Rock. The Cuilcagh Dyke has a fundamental effect on the hydrology. This dyke, a massive sheet of dolerite 25 km long, cuts through the Carboniferous sedimentary rocks of the area along a line trending north west/south east. Because it is an almost total barrier to the passage of groundwater, it isolates the Shannon Pot catchment on its southern side from the Ture and Hanging Rock catchments to the north. Two sinks feed the Shannon Pot System, one, south of the border, the second draining into Tullynakeeragh Gravel Lake. Both resurge at Shannon Pot, the source of the river Shannon, in Co. Cavan. There is no proven link between water sinking at Gortaree and the resurgence at Ture just over the border but all evidence suggests this is probable. The Hanging Rock catchment resurges at the two Hanging Rock Risings but usually only the East Rising is active. Interesting surface karst occurs in the area, particularly the limestone pavements (about 1km˛ in the area) and dolines, although land improvement appears to have caused some damage. The area has not been thoroughly surveyed for surface features but large areas of good pavement are known to be present. There is one notable dry valley, the Fosstra, with two relict caves, and in Killykeeghan townland there are textbook examples of perched erratics (sandstone boulders standing on limestone plinths). Speleologists believe that there are substantial underground systems here and research is still active. There is an urgent need to survey the surface features to identify possible sites worthy of protection before they are threatened. Much of the known interest is within the National Nature Reserve.

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