|Cladagh River rising at Marble Arch.|
| The Marble Arch Cave System and its associated karst features are considered to be amongst the finest in Britain and Ireland. Williams (1970) states; "Geomorphological knowledge of the Marble Arch Upland and indeed of all the other upland karst in this part of Ireland is exceedingly poor which is surprising since the karst is among the finest in the British Isles".|
| The Marble Arch System has the largest catchment and is the most extensive, largely active, karst drainage system in Northern Ireland. The various passages within the system display a wide range of development features and many varieties of speleothems are found within the system. Marble Arch is the largest karst resurgence in Ireland and is probably one of the largest in the U.K.|
| The surface features associated with the system are particularly well developed, and include the best examples of episodic streams, dry valleys, blind valleys, steepheads, collapse dolines, solution dolines, limestone gorges, natural arches and karst windows in Northern Ireland.|
| The Marble Arch Karst lies within all or parts of Tromogah, Aghnahoo, Legnabrocky, Legg, Skreen, Leeffa, Legahorna and Gortmaconnell townlands. The area contains many caves, all of which are part of, or are intimately associated with, the Marble Arch Cave System. This comprises approximately 6.5km of hydrologically connected caves whose associated streams resurge at the Marble Arch.|
| The majority of these caves have been physically linked as a result of cave exploration dating from 1895. The cave is a mature dendritic river system with both active and abandoned passages. The surface karst in the Marble Arch area shows a wide range of mature surface karst features and is the best developed surface karst in Northern Ireland.|
| History of Exploration: Systematic exploration in the Marble Arch system began with the visit by Martel of Paris and Jameson of Dublin in 1895 who visited the Grand Gallery, Lower Cradle and Monastir Cave. Between 1907 and 1947 the YRC explored Pollasumera (1907,8), Pollbwee (1908), Upper Cradle (1908), Lower Cradle - Grand Gallery connection (1935), Skreen Hill 1 (1936) and Pollnagollum of the Boats (1938,9).|
| In the 1950's the CPC explored Pollnabrindle (1950) and Legnabrocky Pot (1953). Pollasillagh was explored upstream in 1956 (W. Reay) and downstream in 1957 (H. Holgate). SMCC explored Aghinrawn, Bruce's Pot, Upper Cradle and the Monastir extensions in 1958. John Thomas' Hole was explored by John Thomas McGovern in 1964.|
| Within Marble Arch itself a major extension was discovered in 1966 when Boon and Cobley discovered the bypass from Skreen Hill 1 into Skreen Hill 2 and Legnabrocky Way. The Skreen Hill 3 Sump was passed by a combined ICC - CDG party in 1967, the salient|
| features (Frake's Way, Ogden's Hall and Vicker's Choke) being named after three of the explorers who died in a flood in Mossdale Caverns (Yorkshire) later that year. The RG made a number of extensions in various parts of the system in the 70's and the Upper Cradle, Lower Cradle and John Thomas' downstream sumps were explored by the CDG in 1978.|
| Major speleological sites: Marble Arch Cave (H121 344), Pollasumera (H1302 3319), Pollnagollum (H1278 3386), Monastir Caves (H119 335), Aghinrawn Cave (H1278 3338), Pollbwee (H1198 3360), Sruh Croppa Bridge Sink (H1163 3360), Sruh Croppa Cave (H1160 3365), Island Pot (H1164 3369), Cat Pot (H1172 3384), Cat's Hole (H1168 3373), McGovern's Sink, Freda's Hole (H1164 3394), Pollthanarees (H1173 3392), Mastodon (H1183 3393), Pollasillagh (H1183 3403), John Thomas' Hole (H1188 3409), Pollnagapple (H1201 3405), Upper Cradle Hole and Lower Cradle Hole (H120 341).|
| Minor speleological sites: Schoolhouse Cave (H1072 3334), Carricknacoppan Caves (H12 32), Pollnabrindle (H1266 3341), Legnabrocky Pot (H1220 3370).|
| Total surveyed cave: 7000m+, 70m deep.|
| Area of exposed limestone pavement: 200m2.
Catchment area: ~27km2.
Volume of water in system (estimated): 1-1.5 CuMecs (Cubic metres of water per second) in normal conditions (95,000,000 to 142,500,000 litres per day). 10+ CuMecs in extreme flood (950,000,000 litres per day).
Note: The Ordnance Survey name the three major rivers forming the catchment for the Marble Arch System from east to west as follows; no name, Owenbrean and Sruh Croppa. It has been known for some time that these names are incorrect and should in fact be referred to as the Owenbrean (sinking at Pollasumera), the Aghinrawn (sinking at Monastir) and the Sruh Croppa (sinking at or near the Sruh Croppa Bridge in normal conditions).
| I - Hydrology|
| The bulk of the water draining northern Cuilcagh Mountain, in three large rivers and a number of smaller streams, collects in Marble Arch Cave. The waters of the three main rivers, and associated minor tributaries, finally meet at The Junction in Marble Arch Cave before emerging at the Marble Arch as the Cladagh River. This resurgence, at the head of the Cladagh Glen, is one of the largest karst risings in the U.K.|
| The Owenbrean River partially sinks in its stream bed to drain to the Prod's-Cascades system but the bulk of the water (especially in flood conditions) sinks at Pollasumera and forms the stream seen in Pollnagollum of the Boats and the Skreen Hill passages in Marble Arch. A tributary stream (probably fed by sinks at Legnabrocky Pot, Carson's Pot and PollUladh) flows from Legnabrocky Way and joins the Owenbrean in Skreen Hill 2.|
| The Aghinrawn River sinks at Monastir Sink and flows from here to Cradle Hole, meeting the Sruh Croppa somewhere between Upper Cradle and John Thomas' Hole.|
| The Sruh Croppa River sinks at various localities depending on water levels. In normal conditions it sinks into a number of sinks upstream of the Sruh Croppa Bridge but in high water it continues along the normally dry river bed to sink at Cat's Hole. In extreme flood the river continues past Cat's Hole to sink between Pollasillagh and John Thomas' Hole.|
| There a large number of minor sinks and risings within the Marble Arch area. Many of these drain to Marble Arch, entering the system via a number of small inlets. Others pursue an independent course to the Cladagh River.|
| II - Underground Karst|
| The caves within the Marble Arch Karst are divided into 5 groups for convenience; Marble Arch Cave, the Owenbrean River Caves, the Aghinrawn River Caves, the Sruh Croppa River Caves and Associated Sites.|
| For site specific information and any associated photographs see the following reports:|
| 1 - for Marble Arch Cave see Key Site 347 - Marble Arch Cave.|
| 2 - for the Owenbrean River Caves see Key Site 348 - Pollasumera Key and Key Site 349 - Pollnagollum.
3 - for the Aghinrawn River Caves see Key Site 350 - Monastir Caves, Key Site 351 - Aghinrawn Caves, Key Site 352 - Pollbwee, Key Site 361 - Pollnagapple, and Key Site 362 - Upper and Lower Cradle Hole.
4 - for the Sruh Croppa River Caves see Key Site 353 - Sruh Croppa Cave, Key Site 355 - Cat's Hole, Key Site 356 - McGovern's Sinkand Freda's Hole, Key Site 357 - Pollthainarees, Key Site 358 - Mastodon, Key Site 359 - Pollasillagh, Key Site 360 - John Thomas' Hole, and Key Site 1083 - Cat Pot.
5 - for Associated Sites see Key Site 354 - Island Pot, Key Site 363 - Schoolhouse Caves, Key Site 364 - Carricknacoppan Caves, Key Site 365 - Pollnabrindle, and Key Site 366 - Legnabrocky Pot.
III - Surface Karst
Collapse Dolines: There are a number of collapse dolines associated with the Marble Arch System. Of these the largest and most impressive are Glass Rock Hollow, Cradle Hole and Pollnagollum of the Boats. Glass Rock Hollow is a large (40m x 150m) doline formed in completely dolomitized Knockmore Limestone and lies along the trace of the Pollnagollum Fault and above the underground course of the Owenbrean River.
Cradle Hole is situated close to the junction of the Sruh Croppa and Aghinrawn Rivers and Pollnagollum of the Boats is situated on the underground course of the Owenbrean River, dividing Pollnagollum cave from Skreen Hill 3 passage in Marble Arch.
Solution Dolines: There are a large number of varying sized solution dolines in the Marble Arch area. In a number of cases these dolines are formed along a linear trend. The large solution dolines, Pollreagh,|
Polligarria and Pollawaddy, are the largest closed depressions in County Fermanagh and may have an element of collapse associated with them.
Blind valleys: The courses of the Owenbrean and Aghinrawn Rivers are excellent examples of blind valleys, with major streams cutting gorges into the limestone, prior to sinking into caves at the base of large (up to 30m high) cliffs.
Dry Valleys: There are a large number of dry valleys in the Marble Arch area. The largest of these trend from the major sinks of the Sruh Croppa and Aghinrawn Rivers towards the present resurgence and the Cladagh Glen. Other dry valleys include the East and West Gorges (situated to the east of Pollbwee and west of the Show Cave road) and a small dry valley, initially continuing west from the end of the Pollasumera gorge before trending northwest of Glass Rock Hollow. This dry valley is subsequently obscured by thick drift in the Aghinrawn - Legnabrocky Rock area.
Steephead: Marble Arch rising is an excellent example of a steephead, referring to a resurgence located at the base of a cliff at the head of a river valley.
Natural Arches: Marble Arch and an example in the West Gorge
|Pollreagh, a major doline.|
consist of a short section of roofed gorge.
Karren: Limestone pavement is poorly exposed in the Marble Arch area.
|Natural arch in West Gorge.|
|Limestone pavement and mud reef knoll at Killykeegan.|
| Marble Arch is the largest karst resurgence in Northern Ireland and is one of the largest in Britain and Ireland. The caves and surface karst associated with the Marble Arch System represent the best karst development in Northern Ireland and compare well with the classic British karst areas such as the Yorkshire Dales.|
| A wide range of surface and underground features are present and many of the features and processes of temperate karst development can be demonstrated here. Polyphase development of the system and concepts of karst stream capture and rejuvenation are especially evident. The cave contains considerable amounts of clastic and chemical deposits which have major potential for further scientific research.|
| I - Hydrology|
| The Marble Arch Cave System carries the vast bulk of the drainage of Northern Cuilcagh Mountain. This water is concentrated into three large rivers and a number of smaller streams. The under- ground hydrology is well understood, the various streams having been explored for much of their course underground. There are a number of minor flow pathways which remain unresolved although, in the main, it is only short sections of unexplored cave and exact confluence points which have not been determined.|
| The Cuilcagh Dyke, a thick, impermeable, dolerite igneous feature,|
exerts a significant control on the distribution of the sinks for the Marble Arch System, the Sruh Croppa and Aghinrawn Rivers sinking soon after crossing this feature. The Owenbrean River sinks in its stream bed to the south of the Cuilcagh Dyke,
|Cuilcagh Dyke in Monastir Gorge.|
presumably due to the presence of a N-S oriented structure offsetting the trend of the dyke, allowing water to flow under- ground to the north while crossing the dyke trend.
|Cuilcagh Dyke, Owenbrean River.|
| The system, as a whole, shows a major dendritic drainage pattern, a significant proportion of which is underground.|
| II - Underground Karst|
| The Marble Arch Caves are a mature dendritic vadose river cave system with a number of active phreatic sections. The cave passages are largely fracture controlled, although shale beds, where present, exert a significant control on passage morphology. The system shows a wide range of morphological and genetic features indicating that the Marble Arch System is a mature karst system, predating 75,000 BP.|
| The caves associated with the Owenbrean River are largely fracture controlled caves, initially trending N-S along a major fault zone exposed in Pollnagollum of the Boats and Skreen Hill 3. This trend changes in Skreen Hill 2 and Skreen Hill 1 where the structure is predominantly E-W. Legnabrocky Way is a large abandoned stream passage which has been reinvaded by a much smaller recent stream. Large scale breakdown and clastic deposits are present here giving a possible indication of the relative age of this passage.|
| Legnabrocky Way and the N-S oriented portion of the Skreen Hill Sump Bypass can be interpreted as abandoned stream passages which may have previously carried the Owenbrean River. This stream is interpreted to have subsequently been captured to sink at Pollasumera, to flow through the Pollasumera-Pollnagollum-Skreen Hill passages. The previous resurgence for this streamway is most likely to have been associated with Cascades Rising Cave, the Owenbrean River entering the Prod's-Cascades System as a major tributary in the Boulder Series.|
| The Monastir Cliff Caves are a series of abandoned inlets associated with the underground course of the Aghinrawn River, which has downcut below the level of these caves and is currently following a more recent, largely phreatic course (Monastir Way), to Upper Cradle. Upper Cradle and Lower Cradle are large active vadose streamways, presumably part of the Aghinrawn course before the Monastir Way section developed.|
| The Sruh Croppa caves are largely abandoned in normal conditions, the Sruh Croppa River following a largely unexplored phreatic system underneath the present level of the Sruh Croppa Caves. The caves are only active in flood conditions. The Sruh Croppa emerges from this phreatic zone in Lower Cradle, again presumably part of the course before the current phreas developed. The large collapse at Cradle Hole is interpreted as being due to increased erosion at a palaeoconfluence of the Sruh Croppa and Aghinrawn Rivers predating their current phreatic courses.|
| No evidence for phreatic drainage or fossil passages has been discovered in the main passage downstream of Cradle Hole. Lower Cradle and the Grand Gallery are interpreted as the only under- ground course of the combined Sruh Croppa and Aghinrawn streams.
The passages connecting the Junction with New Chamber are interpreted as the previous course of the Owenbrean River from Skreen Hill 1 to The Junction. These passages have now been largely abandoned and are only active in flood conditions due to capture of the Owenbrean River by the sumped passage connecting the end of Skreen Hill 1 to The Junction.
III - Surface Karst
The surface karst in the Marble Arch area shows many features common to a mature upland karst area. Although limestone pavements are poorly developed due to extensive Quaternary deposits, other features are particularly well developed.
The Sruh Croppa and Owenbrean Rivers are good examples of episodic streams, the flow sinking further downstream in the river beds as flow increases. Monastir and Pollasumera are well developed blind valleys, with typical limestone gorges immediately upstream. The development of these gorges and blind valleys can be interpreted as resulting from downcutting induced by glacial deepening of the MacNean Valley.
The area contains many dry valleys, the most evident being those trending from Monastir and Cat's Hole towards the head of the Cladagh Glen. These may have been formed by surface river flow in permafrost conditions. The small dry valley continuing from Pollasumera towards Legnabrocky Rock may be related to a palaeocourse of the Owenbrean River, which may have originally sunk somewhere to the west of the current Owenbrean River passage between Pollasumera and Legnabrocky Rock.
The area of the present resurgence of the Cladagh River, the Marble Arch and the many associated collapse dolines are typical of resurgence collapse, a steephead forming as passages at the resurgence progressively collapse upstream into the river below.|
| The caves and surface karst of the Marble Arch System and surrounding area are one of the best developed and most extensive upland dendritic vadose river caves in Britain and Ireland. Much of the surface and underground features remain in a good state of conservation, although some parts of the system have been significantly altered by commercial development and erosion from frequent use by cavers and outdoor education - pursuit groups.|
| For information and reference lists on the systems and features of other karst areas within the Marlbank-Cuilcagh Mountain Region see;|
|Key Site 1153 - East Cuilcagh Key Site 1154 - Tullyhona, Brookfield and Trien Key Site 1155 - Prod's Pot - Cascades Rising Area Key Site 1157 - Western Marlbank.|
|A large number of biological specimens have been collected from the Marble Arch System in the past and these are listed in Hazleton et al. (1974). Sites from which biological records have been compiled are Bruce's Pot, Legnabrocky Pot, Marble Arch Cave, Pollasumera, Pollnagollum and Upper Cradle Hole. In addition, otters, brown trout and eels have been recorded from Lower Cradle.|
|Planning:||HISTORY OF EXPLORATION Systematic exploration in the Marble Arch system began with the visit by Martel of Paris and Jameson of Dublin in 1895 who visited the Grand Gallery, Lower Cradle and Monastir Cave. Between 1907 and 1947 the YRC explored Pollasumera (1907,8), Pollbwee (1908), Upper Cradle (1908), Lower Cradle - Grand Gallery connection (1935), Skreen Hill 1 (1936) and Pollnagollum of the Boats (1938,9). In the 1950's the CPC explored Pollnabrindle (1950) and Legnabrocky Pot (1953). Pollasillagh was explored upstream in 1956 (W. Reay) and downstream in 1957 (H. Holgate). SMCC explored Aghinrawn, Bruce's Pot, Upper Cradle and the Monastir extensions in 1958. John Thomas' Hole was explored by John Thomas McGovern in 1964. Within Marble Arch itself a major extension was discovered in 1966 when Boon and Cobley discovered the bypass from Skreen Hill 1 into Skreen Hill 2 and Legnabrocky Way. The Skreen Hill 3 Sump was passed by a combined ICC-CDG party in 1967, the salient features (Frake's Way, Ogden's Hall and Vicker's Choke) being named after three of the explorers who died in a flood in Mossdale Caverns (Yorkshire) later that year. The RG made a number of extensions in various parts of the system in the 70's and the Upper Cradle, Lower Cradle and John Thomas' downstream sumps were explored by the CDG in 1978.|
|Management:||The Marble Arch Cave System has a wide and varied group of interested parties involved in using the cave. Much of the easily accessible cave (Grand Gallery, Skreen Hill 1) is used as a tourist show cave, managed by Fermanagh District Council. Marble Arch Cave (Grand Gallery and Skreen Hill 1 & 2) and Lower Cradle are extensively used by education groups and outdoor pursuit groups. All parts of the system are used by caving groups. Internal threats: 1 - Show Cave: The development of Marble Arch Show Cave has led to a wide variety of major and minor modifications within the cave system, a number of which have significant implications for the cave features and environment. The show cave extends from the Wet Entrance to the Junction, and to Skreen Hill 1 via 'New' chamber. Modifications to the cave Pathways:- A significant amount of concrete material has been introduced to the cave passages in the form of pathways. Considerable amounts of natural sediments (sandstone cobbles) within the cave were utilised in the construction of the pathways. Lighting:- A large number of light fittings have been installed within the cave. A common problem with lighting in show caves has been the growth of mosses, algae and lichens on cave walls and calcite speleothems, due to the presence of light and heat.|
|Marble Arch: lamp flora, Skreen Hill One.|
|Marble Arch: lamp flora, Skreen Hill One.|
Artificial Entrance:- During the development of the show cave an artificial entrance (The Armco)
|Marble Arch: lamp flora, Skreen Hill One.|
was constructed to provide a second exit from the system close to the end of the tourist route. This was effected by excavating a drift filled doline overlying the Skreen Hill 1 passage. The addition of this entrance has changed the cave climate in Skreen Hill 1, introducing a significant draft which may lead to alterations in speleothem growth patterns. Weirs:- A number of artificial weirs have been constructed at various points within the system. Of these two have altered the cave environment significantly. One, situated at the Wet Entrance, has been constructed to deepen the lake leading to the Junction to allow sufficient water to use boats on the lake. The second has been constructed upstream of the end of the show cave, to slow flood pulses in the Skreen Hill 1 streamway. The first weir has succeeded in deepening the entrance lake, but has also increased the amount of sediment deposition in this area. The second weir, while slowing the flood pulses to some degree, has led to serious backing up of water in the passages above the weir where this has not been previously recorded. Surface modifications:- A large visitor centre, reception and cafe complex has been constructed adjacent to the entrance of the show cave to service visitors to the cave. There are a number of pollution hazards associated with the human activities associated with this complex. While these have generally been minimised, with no visible pollution from, for example, sewerage or cement, diesel has leaked into the system from corroded feed pipes in the central heating system of the complex. 2 - Outdoor Education - Pursuit Centres: The sites predominantly used by these groups are Lower and Upper Cradle, which are largely high-medium energy systems. Use of these sites by these groups has been encouraged by SUI (honeypotting), as they are good examples of natural cave which are capable (with educated usage) of sustaining relatively high numbers of visitors. 3 - Cavers: Marble Arch caves are a popular system for cavers, particularly with groups including relative novices. Certain parts of the system have suffered erosion over the years, particularly low energy sections such as the Skreen Hill Sump Bypass and Legnabrocky Way. Within the Skreen Hill Sump Bypass some mud deposits on the main route have been disturbed and a number of minor speleothems damaged. In Legnabrocky Way mud deposits have been disturbed and speleothems damaged. Areas which are considered especially sensitive have now been taped by local cavers. Conservation information on this section of cave has been published by SUI. External Threats: The external threats to the Marble Arch Cave System include pollution from agricultural and other effluent, increased sediment input from gripping and peat extraction within the catchment of the system, infilling of dolines and covering of free karren during land improvement and construction of buildings, and dumping of fallen animals and household waste in potholes, sinks and dolines.
|Marble Arch: Skreen Hill One, looking upstream from Armco steps.|
|Threats:||Tourism related development; pollution from farming and other effluent; dumping; increased sediment input.|
|Uses:||Tourist attraction; outdoor pursuits; caving; educational parties; research.|
|Potential:||Future exploration within the Marble Arch System is likely to be directed at establishing links between areas of cave which are currently only linked hydrologically. A number of areas where through trips could be established are present but it is unlikely that local cavers will attempt to engineer such trips. There may be a number of high level fossil passages which remain undiscovered in the Legnabrocky Way - Skreen Hill Bypass areas. There is considerable potential for academic research within the Marble Arch System.|