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Earth Science Conservation Review
| Noon's Hole-Arch Cave; Noon's Hole-Arch Cave System | Fermanagh |
| Site number: | 405 | File Number: | H04 |
| ESCC: | IC | ||
| Locality Type: | Cave, Cave System | Status: | ASSI |
| Grid Reference: | H09364830 | ||
| Google maps: | 54.38371,-7.85684 | ||
| County: | Fermanagh | Council area: | Fermanagh & Omagh District Council |
| Period: | Quaternary, Carboniferous | ||
| Stages: | Asbian, Holocene, Visean | ||
| Lithostrat: | Dartry Limestone Formation, Glenade Sandstone Formation, Glencar Limestone Formation, Knockmore Limestone Member, Meenymore Formation | ||
| Site Description | |
|---|---|
| Description: | |
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. Noon's Hole (230m amsl) lies at the contact between the Dartry and Knockmore limestones in a large (200 x 100m) shallow depression. The relatively small surface entrance to Noon's Hole pothole leads directly to the 82 metre vadose shaft complex below. The first few metres of the shaft are developed in the cherty facies of the Dartry Limestone in a dominant fracture. 15m from the surface the shaft development, while still on the fracture, is in the purer Knockmore Limestone and the diameter increases to ~6m before a ledge breaks the waterfall 35m from the surface. The shaft is split by a natural bridge at this ledge and the water flows to one side to fall a further 12m to the next ledge. This ledge catches the sediment load of the stream (and any other natural or man-made material falling down the shaft) creating a cobble floored pool. The fluted walls at this level expose fine crinoid fossils. Again, the shaft splits, and in normal water flow a series of vertical conduits takes the stream down to a sump pool. An adjacent periodically active shaft series leads to a cobble floored chamber with a canyon passage leading into the horizontally developed passages of the Afternoon Series. These phreatic joint controlled passages flood regularly to the roof but they do not carry more than a trickle in normal water levels. Deep pools and a vadose trench are found in the floor and in the roof large pendants are common. 50m from the base of the shaft there is a T junction and the downstream flow is east through passage of similar character but with an increasing number of deep pools. After 150m the stream flows into a sump 88m below surface (142m amsl). The main flow from the entrance shaft joins somewhere in this section but it is not discernible. The 45m phreatic section leads to the Arch 2 streamway. The passage leading west at the T junction is only active in high water, bringing water from the Afternoon Series upstream sump. The passage walls are clean to a height of 1.75m and above this level they are coated in mud with a manganese oxide crust. The predominant E-W joint control in this area is crosscut by three N-S fault fractures at No Ones Hole, Fault Chamber and Crucifixion Crawl. Breccias, fault mullions and slickensides can be seen clearly on the fault faces. The Fault Chamber fault is transtensional and there is a notably thick breccia in this area. Crucifixion Crawl is a 15m long small tube connecting the Afternoon Series to High Noon's. Where they meet the High Noon's passage is an archetypal elliptical joint controlled passage (0.75m wide by 5 m high) with a vadose trench in the floor. Crucifixion Crawl meets it at right angles with upstream to the south and downstream north. This passage is only active in flood but at one point 20m downstream the active streamway can be heard below. 300m of upstream passage can be traversed passing areas of major breakdown to a sump which lies ~400m to the north of Pollanaffrin and Pollaphylla. Downstream of Crucifixion Crawl the passage character changes. A flood water outlet on the east wall lies at the beginning of a sediment infill floor and fault associated breakdown is encountered in the roof. A 10m section of fossil phreatic tube half filled with sediment has a fine half tube in the roof joint before the passage becomes bedding controlled. 40m of low (1.5m), wide (7m), flat roofed, sediment-floored passage has fine stalactites, stalagmites, columns and static pools before Artie's Chamber. At Artie's Chamber a side passage joins High Noon's from the west. From Artie's Chamber to the terminal High Noon's Sump (150m) five inlets join the passage on the left wall from the west and north as the passage changes direction through 180 deg. The first inlet joins the main passage at Artie's Chamber, emanating from an aven in the left branch of the side passage. The right branch of the side passage intersects the F.A. stream flowing to the south. The fossil sections of the second inlet passages (Nollaig Way and Christmas Gallery) have good speleothems, particularly straw stalactites. The third and fourth inlets have not been extensively explored but the fifth gives access to Chamber Passage and the connection with Arch 2. Where these inlets join High Noon's there are a number of flowstone features and gour pool suites. Chamber Passage is a large area of collapse some 80m long and in parts up to 10m wide which is reached by negotiating at boulder collapse in the fifth inlet. Streamlets have formed gours pools on the floor of Chamber Passage; between the boulders and some of the collapse boulders are calcite covered. On the eastern wall at the northern end of the Chamber Passage static water lies between the boulders in pools, and tight joints and rifts lead to the Ox Bow in Arch 2. Through Arch 2 (1km long) many classic passage forms and cave deposits are present. Just downstream of the sump from the Afternoon Series, phreatic cross sections with a vadose canyon are seen before the passage develops into a vadose streamway averaging 9m by 9m. The stream runs over a boulder strewn floor bounded by mud and sand banks. Above normal stream levels there are many areas of calcite speleothems developed on the roof, walls and sediment banks. The water from High Noon's enters this passage from the west from the Main Stream Inlet Sump 50m upstream of the relict Ox Bow. At the calcited boulder choke at the southern end of the Ox Bow is the connection through to Chamber Passage. The Ox Bow passage displays classic bedding breakdown. Returning to the active streamway past the Ox Bow, the passage progressively turns through 180 deg. over 100m joining a strong joint trending south. The passage has a number of deep lakes and many high avens in the roof with calcite speleothems well developed in the roof joint. Areas of collapse also host fine speleothem deposits above the streamway including a particularly impressive field of stalagmite bosses and a 2m calcite column. A chamber and major area of breakdown precedes the change in passage character from active vadose passage to an active phreatic zone. In this area the joint controlled, predominantly phreatic Sump Inlet Passage joins the main conduit from the south. The water emerges from the Arch sumps into the Arch 1 streamway which is similar in character to parts of Arch 2. A series of deep lakes interspersed with boulder floored streamway leads to the resurgence. As with Arch 2 passage there are high avens in the roof and just before the resurgence the passage is crosscut by a number of major fissures. There are some minor areas of speleothem deposits, particularly in Formation Passage, and breccia is also evident in the only major inlet passage at Midway Chamber. | |
| Notes: | |
Noon's Hole-Arch Cave System is a feature of the Noon's Hole-Arch Cave area of the Belmore, Ballintempo and Tullybrack Uplands. For general information on the systems and features of the Noon's Hole-Arch Cave area, including this one, and a reference list, see site description 'Belmore, Ballintempo & Tullybrack Uplands; Noon's Hole-Arch Cave'. | |
| Keywords | |
|---|---|
| Minerals: | Calcite |
| Rocks: | Breccia, Chert, Limestone |
| Fossil Groups: | Crinoid |
| Structures: | bedding, fault, joints, rift, slickensides |
| Geomorph: | breakdown, cave, cave pearls, clastic sediments, column, dendritic river cave, flowstone, gour pool, helictite, natural bridge, organic sediments, speleothem, stalactite, stalagmite, straw, sump |
| Measurements | |||||
|---|---|---|---|---|---|
| Length: | 3500 m | Width: | Height: | ||
| Depth: | 120 m | Area: | |||
| Access | |
|---|---|
| Threats: | Accidental damage by cavers; dumping of household and farm waste; farming effluent. |
| Record type: | ESCR report | ||
| Entered by: | Doughty, P.J. | ||
| Last updated: | 24 Dec 2003 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Noon's Hole-Arch Cave; Noon's Hole-Arch Cave System, County Fermanagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=405. Accessed on 2026-11-08. |
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