| Site Description |
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| Highlights: |
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| The Noon's Hole (Sumera) shaft and the system's resurgence at Arch Cave (Ooghboraghan) hold important positions in both speleological and local history, having been visited and described by Martel (1895) and as the location of the involuntary descent by the unfortunate traitor Dominic Noon. |
| To the modern speleologist the expedition from sink to resurgence is regarded as one of the finest in Britain and Ireland. This traverse includes the descent of the deepest and finest pothole in Ireland, negotiating the kilometre of large (average 9 x 9m) speleothem-rich active streamway of Arch 2, diving through a phreatic section and emerging at the magnificent Arch Cave. The total catchment area is ~3.5km2 and, while the surface has a number of interesting karst features, there is little indication of the fine and complex cave system below. |
| Introduction: |
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| The Noon's-Arch area consists of a series of benches and scarp slopes trending from the Big Dog uplands in the west to the Sillees valley in the east. The catchment is bounded to the north by the, as yet undefined, karst watershed between the Noon's-Arch System and the Pollnamadda (Pollaraftra) drainage. To the south the area is bounded by the Pollanaffrin fault which appears to form a hydrological boundary. Within this relatively small surface area a number of streams flow east from the Glenade Sandstone plateau and sink at, or near, the Meenymore Formation- Dartry Limestone contact. The water resurges from a large cave entrance, Arch Cave at the Dartry-Glencar contact and cascades down a series of waterfalls to the valley floor. |
| Major Speleological Sites: Noon's Hole (H0936 4830) - Arch Cave (H1037 4790), total surveyed passage length 3500m, total depth is 120m and the main shaft is 82m deep, Pollanaffrin (H0935 4754) surveyed passage length 245m. |
| Minor Speleological Sites: Aughakeeran Pot (Pollaphylla or Pollasod) (H0934 4765), Seltanahunny Sink (H0896 4860), Old Barr Sink (H0924 4844), Crunthelagh Sink (H0937 4793), Killydrum sink (H0995 4771). |
| Surface sites: Extensive limestone pavement, Sheet 191 and sheet 210 in grid squares H08 49 (southeast corner); H09 49 (southwest corner); H09 48 (large area); H09 47 (small area in north). |
| Total length of surveyed passage: ~3745m. Approximate area of exposed karren: ~1km2. Noon's-Arch catchment area: ~3.5km2. Total area: ~3.5km2. |
| Description: |
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| I - Hydrology |
| Rainfall gathering on the peat covered Glenade Sandstone plateau of Glenkeel and Old Barr flows west and falls over a scarp at the Glenade-Meenymore contact on to a limestone bench between the 240m and 230m contours. On the bench the streams eventually sink in the Dartry Limestone to join a complex underground drainage system developed in the Knockmore Limestone. One major stream sinks into Noon's Hole and another sinks at Pollanaffrin to the south. A number of smaller allogenic sinks are found on the continuation of the limestone bench north towards Pollnamadda. On a lower and less prominent bench along the 190m contour, autogenic water sinks at Killydrum and other unnamed sites. |
| The stream which sinks at Noon's Hole flows via a phreatic section to Arch 2 passage and resurges at Arch Cave (Ooghboraghan). This stream has been followed for its entire underground route. The water sinking at Pollanaffrin and Pollaphylla has not been dye traced but is assumed to enter the cave through the boulder choke in High Noon's Left. Its course cannot be followed though High Noon's, and it is assumed to join the stream sinking at Noon's Hole via the Main Stream Inlet Sump in Arch 2. |
| Prior to reaching Arch 2 the High Noon's stream is joined by a number of inlets presumed to be derived from sinks on the surface to the north and northwest of Noon's Hole (e.g. Old Barr Sink and Seltanahunny). This series of inlets enters the passages from Artie's Chamber to Chamber Passage in High Noon's. The main stream in Arch 2 is joined by two further inlets; one enters from the north via Aliway and the other (which is assumed to be from Killydrum sink) enters from the south via Sump Inlet Passage. The resurgence for the main stream is at Arch Cave at 100m amsl forming a tributary to the Screenagh River. |
| II - Underground Karst |
| (i) Noon's Hole-Arch Cave System |
| The Noon's Hole-Arch Cave is a complex dendritic system controlled by a set of dominant N-S fissures which are linked by a weaker set of E-W joints. Vertical and horizontal passages are developed predominantly in the Knockmore Limestone Member which in this area is dipping gently (~5 deg.) to the west. |
| For detailed site descriptions see; |
| Key Site 405 - Noon's Hole-Arch Cave System |
| (ii) Pollanaffrin |
| For detailed site description see; |
| Key Site 407 - Pollanaffrin. |
| (iii) Minor speleological sites |
| For detailed site descriptions see; |
| Key Site 408 - Aughakeeran Pot Key Site 409 - Seltanahunny Sink Key Site 410 - Old Barr Sink Key Site 411 - Crunthelagh Sink Key Site 412 - Killydrum Sink Key Site 413 - Limestone pavement. |
| III - Surface Karst |
| The two benches separated by a scarp dominate the topography of this area. The upper bench is comprised of the cherty facies and Knockmore Limestone Members which dip gently west-southwest. The good limestone pavements described in the Pollaraftra area continue south on the upper bench and include an area just south of the car park which contains abundant silicified colonial and solitary rugose corals including Siphonodendron junceum, S. pauciradiale, S. martini and Rotiphyllum sp. |
| Small limestone cliffs and solutional dolines add to the karst landscape in the area, but the most striking surface features are the pothole of Noon's Hole which lies on the edge of a large closed depression, the collapse doline at Pollanaffrin and the episodic stream sinks in the Edenybreslen river bed. At Arch Cave the large vaulted cave entrance, boulder strewn cascades and the waterfalls in the Glencar Limestone below the resurgence are archetypal karst features. |
| Importance: |
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| This small area (3.5km2) contains some of the best underground karst in Northern Ireland. The cave system has the deepest series of unbroken vertical shafts in Ireland, both active and fossil phreatic horizontal passages, a major active stream passage with dramatic speleothem deposits and a classic, free draining, contact controlled resurgence. In speleological history and local history the cave holds an important place. |
| The belt of limestone pavement trending north from Noon's Hole to Pollaraftra is the most extensive and best developed limestone pavement in Northern Ireland. |
| Interpretation: |
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| I - Hydrology |
| The hydrology of the system is complex and the only certainty is the flow of water from the Noon's Hole shaft to the resurgence as the majority of its route can be physically followed. All the other hydrological connections are assumed. There is however some evidence of flow patterns in flood conditions from features in the upstream Afternoon Series. This passage is generally dry but seems to take flood water from High Noon's. The scallop marking clearly indicates the flow in this direction. The water may enter Afternoon via the upstream sump or through Crucifixion Crawl. |
| The passage walls in the Upstream Afternoon series are clean washed to a height of 1.75m and have fine sediments deposited above this level. This indicates initial fast flow then slowing and stilling of the water as the outlet is unable to cope with the volume. Debris indicates that in high flood the High Noon's passage fills almost to the roof but in normal conditions the route taken by the stream is unknown. The High Noon's downstream sump is impassable because of an underwater boulder choke which probably relates to the Chamber Passage break down zone. |
| The Sump Inlet Passage reportedly carries one third of the total flow emerging at the resurgence and in the past, before the discovery of High Noon's, was thought to be fed by water from Pollanaffrin and Pollaphylla. |
| II - Underground karst |
| The phases of speleogenesis in the Noon's Hole-Arch Cave system are, at present, undetermined. The system, however, appears relatively young in comparison to the main passages of Reyfad system, 1.5km to the south. The dimensions of Arch 2 and associated passages suggests a greater volume of water during earlier stages in its formation. There is little evidence that the main flow followed routes other than the known passages. The only exception to this may be indicated by the avens in an inlet passage near the upstream sump of Arch 2. |
| Much of the Afternoon and High Noon's Left passage shows strong phreatic features with some vadose entrenchment. High Noon's Right has undisturbed sediment infilling which indicates that flood water is at present diverted around this area. |
| As the Arch 2 stream passage carries a small volume of water in comparison to its size, there are large areas of abandoned passage above stream level. These areas have many very fine speleothems including straw stalactites, stalactites, stalagmites, columns, curtains, helictites, flowstone and gours. The "minaret" shaped passage cross-section close to Aliway in Arch 2 appears to be of phreatic origin but could equally be a symmetrical erosion notching induced by guarding of the passage floor by clastic sediments. |
| III - Surface karst |
| The surface karst features give little indication of the fine and complex cave system below. The dry valley north of Noon's Hole, the dry valley in which the road now lies and the dry valley of Carricknabiller below Pollanaffrin may be ice edge drainage features. This would also suggest that any passage development or deposition of fluvial sediments during glacial periods was limited due to lack of active water. |
| As with the whole Tullybrack area the karst features are superimposed on a glacially modified topography. |
| Conclusions: |
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| CONCLUSION |
| The Noon's Hole-Arch Cave area has been demonstrated to contain underground and surface karst features which are of National significance. The quantity, quality of karst geomorphological and geological features of scientific interest within this karst unit is important enough to justify any refuse clean up programme which may be needed to restore the quality of the site. |
| Notes: |
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| For information and reference lists on the systems and features of other karst areas within the Belmore, Ballintempo and Tullybrack Uplands see; |
| Key Site 1158 - Belmore Key Site 1159 - Boho Key Site 1160 - Reyfad-Carrickbeg Key Site 1162 - Knockmore-Pollaraftra. |
| BIOLOGICAL INTEREST |
| No biospeleological observations or collections have been undertaken in the Noon' Hole or Arch Cave area prior to this study. During the study limited faunal collections were completed. Bat observations were limited to looking for droppings and cursory examinations of accessible and potential roost sites. |
| The stream carries trogloxenes down the shafts into cave and brings organic material into the system providing food for faunal populations. The trogloxenes observed in the Afternoon Series included leeches and worms (family Lumbriculidae) and a number of the mudbanks were covered in worm casts. Collembola sp. (spring tails), snails and a pink mite were observed browsing on mud surfaces. |
| The fault breccia in Fault Chamber supports colonies of web spinning larva, probably of the fungus gnat (Speolepta leptgaster), and on the water surface of the upstream Afternoon Sump mites and grey flat worms (possibly Crenobia alpina) were observed. A number of fresh water shrimps were also seen in the sump (Gammarus sp.). As no information on recharge to the sump is known, no suggestions on the viability of a cavernicolous population can be given. |
| In Arch 2 streamway a dead rat was observed which is almost certainly associated with dumping of household waste. |
| In Arch 1 entrance small amounts of bat guano were found which suggests intermittent roosting. The stream in Arch 1 supports a fresh water shrimp (Gammarus sp.) population. |