|Belmore, Ballintempo & Tullybrack Uplands; Reyfad-Carrickbeg||Fermanagh|
|Site Type: ||Karst|
|Site Status: |
|District: ||Fermanagh District Council|
|Grid Reference: ||H1046|
|Rock Age: ||Quaternary, Carboniferous (Asbian, Brigantian, Holocene, Visean)|
|Rock Name: ||Carn Limestone Member, Dartry Limestone Formation, Glenade Sandstone Formation, Glencar Limestone Formation, Knockmore Limestone Member, Meenymore Formation|
|Rock Type: ||Breccia, Chert, Limestone, Mudstone|
|Minerals: ||Calcite, Gypsum|
|Other interest: ||bedding, fault, joints, rift, No Data, breakdown, cave, cave pearls, clastic sediments, dendritic river cave, doline, drift, dry valley, flowstone, gour pool, helictite, karren, limestone pavement, organic sediments, pothole, sinkhole, soft calcite, speleothem, stalactite, stalagmite, straw, s|
Summary of site:
In the middle of the east facing escarpment of the Ballintempo uplands, between the Noonís Hole catchment to the north and the Boho Cave catchment to the south, is an area whose dominant interest is the Reyfad/Carrickbeg Cave system. It is almost certainly defined by its geological structural setting, separated by a substantial east-west trending fault to the north (running from Glenkeel and passing through Killydrum and Drumscollop) and a minor fault to the south (passing just north of Pollmore and cutting through Killyhommon village). Here there are five major streams draining over the Glenade and Meenymore Formations on to the Dartry Limestone, where they sink into the subterranean streamways of the Reyfad/Carrickbeg catchment.
The hydrology of this system is complex and appears to be dendritic (branching) but sufficient dye tracing has been conducted for it to be broadly understood and to link all five streams to the Carrickbeg resurgence. The stream entering Polltullybrack is known as the Reyfad Stream; it flows initially slightly west of north for 600m, then swings abruptly south for 200m into Reyfad Main Chamber before passing further south into the Southern Inlet Passage and the long Aghandoo passages and beyond. It has been traced beyond three sumps, a total course of around 3km. At times of extreme flooding the Aghandoo Passages are incapable of taking the full flow and water backs-up to the Southern Inlet Passage where foam has been observed 20m above the streamís normal level.
A second stream feeding Watsonís Sink continues via Watsonís Way into the North West Inlet which joins the main Reyfad Stream at the Southern Inlet Passage. The distance to this point is around 700m.
Two streams drain into Waterfall Sink, a short shaft into a tunnel terminating in a small chamber. The water drains through its floor and appears to feed into the roof of New River in the main Reyfad system where it eventually disappears into an impenetrable boulder choke.
The stream entering the system through Pollnacrom follows a north-west route, initially for 80m, and then turns into Pollnacrom Downstream, a series of large passages that become narrower and eventually, after 600m, terminate at a sump.
All these streams flow almost directly south from Reyfad to their final sumps in the Dartry Limestone but they emerge, surprisingly, 3.5km to the north east in Carrickbeg Rising Cave.
All the major and minor caves in this system are described individually by site name, as follows:
The major fault limiting the hydrology to the north also has surface expression in a major valley that breaks the line of the escarpment at Carricknaboll, carrying surface waters to Edenybreslen. A terrace in the limestone extends south east for 3km from here, partly covered by blanket bog that clears below the 310m contour. There are many sinks in this area some of which are known to feed the Reyfad system. Between the 300m and 200m contours is a complex landscape of crags and dry valleys, although minor risings and sinks do occur. A further terrace feature is present between the 200m and 150m contours before the final slope to the Screenagh River lowlands. Here the base of the Dartry Limestone is in contact with the shaley limestones of the Glencar Limestone Formation, which is the zone of resurgence along the entire escarpment.
It has been suggested that the large water flows presumed to be needed for the creation of the Reyfad system far exceed the current drainage and probably required the concentrated flow of meltwater down the Carricknaboll valley and seepage into the large depression at Edenybreslen. This would be one explanation for the considerable volume of glacial sediments seen in the caves. Undoubtedly the system was already mature long before the sediments were deposited, towards what is presumed to be the end of the last glaciation. It is possible that the dry valleys between the 300m and 200m contours were temporary resurgences from around this period.
The Reyfad/Pollnacrom/Polltullybrack system is the longest and deepest cave in Northern Ireland, with almost 7km of surveyed passages and a total depth (from the highest entrance to the deepest section) of 193m. It is also the ninth deepest and eighteenth longest in the UK, with the largest passages and the deepest shaft yet found anywhere in Ireland. It is estimated that at least a further 5km of passages remain to be discovered to link the most southerly sump to the main rising. The present cave is almost certainly a mere fragment of a substantial earlier system that existed before the last glaciation. It contains the most extensive glacial and post-glacial deposits of any cave in Northern Ireland. These sediments, yet to be researched, will almost certainly reveal valuable environmental information about the period of their deposition. The Reyfad system is the most important underground karst site in Northern Ireland and is of regional, national and international importance.
The main threats to the cave are from the activities of sporting cavers with sediments and calcite and gypsum speleothems (formations) particularly at risk. Since access is only available to serious cavers with well developed technical skills, the presumption of intelligent care of this aspect of heritage seems reasonable. Damage has undoubtedly occurred as a consequence of the diversion of surface drainage, the dumping of animal carcasses into potholes and the irresponsible disposal of household waste. If these problems can be overcome, a clean-up programme should be devised to restore the area to a near pristine state.