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Marlbank-Cuilcagh Mountain Region; Prod's Pot - Cascades Rising AreaFermanagh
Surface karst: Prod's Pot and Dooneen Rattling Hole depression.
Summary Full report
Site Type: Karst
Site Status:
District: Fermanagh District Council
Grid Reference: H1333
Rocks
Rock Age: Quaternary, Carboniferous (Asbian, Holocene, Visean)
Rock Name: Dartry Limestone Formation, Glenade Sandstone Formation, Glencar Limestone Formation, Knockmore Limestone Member, Meenymore Formation
Rock Type: Limestone, Mudstone, Shale
Interest
Minerals: Calcite, Dolomite
Fossil Groups: Ammonite
Other interest: bedding, fault, joints, rift, No Data, breakdown, cave, cave pearls, clastic sediments, column, conulite, dendritic river cave, doline, drift, flowstone, gour pool, helictite, karren, pothole, sinkhole, speleothem, splattermite, stalactite, stalagmite, straw, sump, varve

Summary of site:

The Prod’s Pot – Cascades Rising system is one of Ireland’s most important caves. In its present state of exploration it is known to be 94m deep and 4.1km long, making it Northern Ireland’s third longest and deepest cave (and Ireland’s seventh longest and deepest). It is also a fine example of a dendritic cave, particularly in its upper reaches.

The overall cave plan is strongly linear for over 2km from its upland feeder sinks to its resurgence in the upper reaches of the Cladagh River gorge. The direction of this line is almost exactly north-west/south-east, the dominant direction of one of the joint pairs (natural fractures) in the area. There are only two entrances to the system: Prod’s Pot itself enters the upper, distal part of the cave; the second is via a deserted rising above the resurgence of the active stream, the Cascades Rising, in the gorge. The following two paragraphs outline the layout and main components of the system. Each section is then described in more detail. Prod’s Pot is the name given to the related series of vertical shafts, the entrance pitches, which provide access to the floor of the main stream passage. Upstream there are two major tributaries: the first, Formation Passage, and the second, the Cascade Inlet leading to the Cascade Inlet Passage. A short distance downstream from the pot along the main stream passage there is a further tributary passing west and then south; this is the Papist Passage. The main passage itself runs downstream for 500m before entering a series of eight sumps over a distance of about 1km, passing into the final section before the resurgence which is the Cascade Rising Cave. Prod’s Pot. The entrance to Prod’s Pot is in a large wooded shake hole (NGR H136337) separated from the adjacent Dooneen Rattling Hole by only 4m of rock. There are five pitches (steps) from the surface to the floor of the main passage—12m, 9m, 10m, 5m and 10m respectively—with traverses and slopes between them. There are also two blind potholes in this complex (i.e. potholes not ending in passages). Upstream from the bottom of the pot is a sequence of chambers with shafts above them (avens) alternating with sections of wide, flooded passages with only a few centimetres of air above water surface. After about 90m, boulders spill into the passage from the right. Formation Passage. A climb over the boulders enters the passage with more avens in the roof and a couple of small side passages after 15m. The main passage continues for a further 10m to a boulder choke. This dry section is decorated with straw stalactites, columns and helictites. Some 5m before the choke, a flooded passage (a sump) on the right can be dived into around 60m of stream passage with chambers above. Boulders and mud are a feature of this final, heavily decorated section. Cascade Passage. Returning to the main passage and continuing upstream through a 30m, partly flooded section, leads to a fine calcite column—the Minaret. After a further 10m Cascade Passage enters from the left at right angles to the main stream passage (following the second direction of the joint pair). 60m of contorted passages lead through two sumps to another right angle turn to the right. 240m of passage passes a further sump with good decorations beyond before reaching a junction. The left branch continues for 240m leading to a chamber cut in boulder clay, a glacial deposit usually at, or near, ground surface. A sump of turbid water is the current exploration limit of this branch. Taking the right turn from the junction, a tight, high rift can be followed for 80m until it sumps. Papist Passage. Returning to the bottom of Prod’s Pot and exploring downstream along the widening rift of the main passage, a large tributary enters on the left after 40m—this is Papist Passage. 30m in, a small decorated side passage enters from the left. After a further 200m there is a sump, beyond which is 300m of passage with two high chambers and three further sumps, the last being the limit of exploration. Returning to the spacious main stream passage and walking 80m downstream reaches Bleeding Heart Passage on the right. This muddy passage, about 40m long, is unusual because it contains a red formation, a colour extremely unusual in the Fermanagh karst. The generous proportions of the main stream passage continue for a further 150m to a huge column—the Connolly Memorial Column—which guards the entrance to a boulder-littered chamber with good formations and a high roof. The main stream passage continues high and wide for the next 250m, with impressive calcite curtains over 6m high, passing through a canal wade before entering boulders. An aven in this area may be the bottom of Carson Pot. The passage continues under a boulder bridge but soon becomes a narrowing rift leading to a confined and flooded section with only a few centimetres between water surface and roof. The passage then opens up into a long, mud-slicked chamber leading to a sump. The Sumps. Over the next kilometre the main stream passage is essentially an enlargement of a single dominant joint fracture with eight drowned sections. It is unusual to find such a string of sumps, since these features are normally confined to the lowest levels of systems at, or just above, the water table. It is possible that shales in the Knockmore Limestone form impermeable floors for long stretches of the stream bed before breaching and releasing the stream to the next, lower level. This is not established by observation and further research is needed. Six of the sumps cannot be avoided but the last two can be circumvented in a relatively dry section called the Sump Bypass. Sump Bypass Series. Following sump no. 6, the main stream flows down a wide passage for 100m to a junction. The contorted left hand passage leads to sumps 7 and 8 but to the right a low, 40m muddy passage—Leprechaun Crawl—emerges under an imposing aven. A descent over boulders and mud leads to a generous passage with many calcite and mud decorations, becoming more confined to a sump of clear water on the right, passed by the main passage. Beyond it widens, becoming spacious for 70m and ending at a low, wet stoop for a further 50m where the main stream, having passed sumps 7 and 8, rejoins the passage. This is followed by a walkable section about 100m long. From here, progress is by descending boulders and then wading, chest-deep, for 70m into a chamber. Mudbank Chamber and the Boulder Series. The chamber is over 100m long and contains a large mud bank with the stream displaced along the right wall. There then follow 150m of wide, high and beautifully decorated passage, ending in the Boulder Series. Here, over 150m of wide passage, almost amounting to two chambers, is floored by a chaotic jumble of boulders, making progress difficult. This area of the cave is at the very base of the Knockmore Limestone and it is likely that there was concentrated limestone weathering at this level for a time before the water opened a larger escape route through the rocks below. The series is left by climbing over a boulder barrier into the final section of the system—the Entrance Series. The Entrance Series. The whole of the system up to this point is eroded into the pure, vaguely bedded Knockmore Limestone Member of the Dartry Limestone, but the exit from the Boulder Series descends into the topmost beds of the Glencar Limestone. This dark, strongly bedded limestone is interleaved with shales and everywhere throughout the region it has proved to be a barrier to cave formation—except here. This final section of the cave is therefore unique with an entirely different pattern of passage development. Low, often wide and wet, flat-out crawls with many ducks lead to small chambers with good formations littered with fallen, tabular slabs and boulders. The well-defined beds yield mostly tight squeezes and a descending series of waterfalls leads to a complex junction and a sand-floored chamber beyond. A further crawl and waterfall descent enter a falling series of tight and confined crawls, finally emerging on the east side of the Cladagh River gorge about 15m above the vigorous main resurgence. The through route of the Series as described here, from Prod’s Pot to the resurgence, is no longer (or at least hardly ever) attempted. The original exploration commenced via Prod’s Pot following its excavation in 1970. From the pot, the upstream and downstream sections were progressively explored until finally sump 6 in the downstream section was passed in 1976. This opened up the Sump Bypass, Mud Chamber and Boulder Series into the Entrance Series and daylight. Only then did excavation above the resurgence give direct access to the Entrance Series. Nowadays the system is treated as two caves—Prod’s Pot (including the downstream sumps) and the Cascades Rising System. The hydrology (water flow) of the system, although still not fully understood, has proved surprising. Unlike the component parts of the Marble Arch system, which are supplied by three surface rivers, there is no such obvious source for the large volume of water flowing through the Prod’s Pot – Cascades Rising system. It would be expected that the sinks in the limestones immediately above and behind the system would drain through it, and they do. More surprising is the demonstration by dye testing of leakage into the system through the bed of the Owenbrean River. The Owenbrean is one of the three rivers feeding the Marble Arch system via Pollasumera and Pollnagollum, although it is significant that the systems are only separated by about a kilometre in their upper reaches. Completely unexpected was the link to the stream flowing into Goat Pot almost 3km to the south-east. This pothole, on the south-eastern slope of Trien Mountain, enters bedded Dartry Limestone beyond the Cuilcagh Dyke (a massive vertical sheet of olivine dolerite, molten when it was injected, that completely cuts across the southern slopes of Cuilcagh). Because the dyke is impervious, it should form a hydrological barrier blocking drainage to the north, but obviously this is not the case with the Goat Pot stream. More research is needed before the system’s water flow is fully understood. This system is a superb example of a dendritic river cave development with strong joint control and a unique entrance series in the Glencar Limestone Formation. It has many areas where the water table is perched above the regional water table (perched phreas) and some outstanding, still pristine calcite and mud cave decorations. Combined with an intriguing regional hydrology, this system is rich in karst interest with unique features and has enormous future research potential. There are many threats to its fragile environment. Anything that affects surface drainage and the quality of water entering the system will have an adverse impact and the entire underground framework needs to be carefully managed. The numerous cave formations, in particular, are in pristine condition at the present time and the main threat to them is chiefly from careless cavers.


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