Boho

Also within

Fermanagh County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Cave / Cavern, Gorge / Ravine, Karst · Mining / Industrial: Quarry · Rock Type: Limestone, Sandstone

Landscape processes: Fluvial, Karst

Description

Boho Cave Boho Cave is the only example of a joint controlled maze cave in Northern Ireland. The estimated 1.5km of explored passage has developed horizontally over an area of some 4000m2 within the Cherty Facies of the Dartry Limestone. It is the seventh longest cave system in Northern Ireland. The system has an active flooded or phreatic zone, a series of episodic passages occasionally carrying water and areas of abandoned passage which host good speleothem deposits. The area also contains a remarkable array of surface karst features including episodic surface rivers and an episodic waterfall, a limestone gorge and river bed with a series of bank risings. In normal conditions, water sinks in the river bed upstream of the cave entrance. Downstream of the Boho Ravine are four river bank risings, two of which have been traced from Pollnagollwn Cave. In wet conditions, large flood pulses are directed to Bobo caves, a small block of limestone in comparison to its large catchment. The phreatic, or permanently flooded, zone of the karst unit is unable to accommodate this increased flow and the episodic passages become active. The dry river bed leading from the Quarry Entrance, including the normally dry waterfall, becomes active in these conditions. The routes taken by the water through the episodic passages are often interrupted by debris which intermittently blocks some passages and redirects erosion. Remnants of false calcite floors and canopies are evidence of reworked sediments. From the episodic sink there are a series of fossil chambers which contain excellent calcite speleothems including straws, stalactites, stalagmites, soft calcite, flowstone, curtains, gour pools and canopies which are developed on the roof, walls and floor. Some flowstone canopies have sandstone pebbles cemented into exposed undersides. Further evidence of other floor levels. Organic debris gathers within some of the chambers and fine sediment banks are also present in which charcoal layers are seen. Such sediment deposits are an important source of information on the system's environmental history. Pollnagollum Cave is a large relict cave passage 100m long which has been re-invaded by a small stream. Many speleological features can be seen in this cave. The small stream drops over the south edge of a collapsed doline and enters the cave. There are a number of areas of straw stalactites on the cave roof and small areas of calcite gours and pools on the sediment floor. There are also remnants of a calcite false floor on the passage walls, evidence of reworked sediments. Boho caves display a number of unique lithological and structural controls on the development of underground passage. The surface karst features contribute further to the significance of this unique site. Mixed base rich woodland is present over part of the site. Notable species present include toothwort Lathraea squamaria, wood fescue Festuca aitissima, birdsnest orchid Neoltia nidus-avis and thin spiked wood sedge Carex strigosa. A population of Daubenton's or water bat Myotis daubentonii roost within the main Boho site. Extensive collections of invertebrates have been made in Boho caves and Pollnagollum which included the cave dwelling Collembolan Schaefferia emucronala. Sections of the cave support a large population of the common cave spider Mela menardi which thrives on species blown into the caves by strong draughts. The only modern Irish record of the cave dwelling water beetle Agabus bigunalus is from Boho. https://www.daera-ni.gov.uk/publications/boho-assi

Species mentioned

Plant communities