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Earth Science Conservation Review
| Largy Quarry | Fermanagh |
| Site number: | 243 | File Number: | H24 |
| ESCC: | ED | ||
| Locality Type: | Quarry (disused) | Status: | ASSI |
| Grid Reference: | H299476 Approximate | ||
| Google maps: | 54.37663,-7.53987 | ||
| County: | Fermanagh | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous | ||
| Stages: | Visean | ||
| Lithostrat: | Ballyreagh Conglomerate Formation, Kilskeery Group, Topped Mountain Sandstone Formation | ||
| Site Description | |
|---|---|
| Highlights: | |
Largy Quarry offers one of the best sections through the upper part of the Topped Mountain Sandstone Formation. Interbedded with the sandstones are conglomerates and pebbly sandstones that are virtually indistinguishable from lithologies normally associated with the succeeding Ballyreagh Conglomerate Formation. | |
| Description: | |
Largy Quarry is located on the east face of Largy Mountain, 5km west of the village of Tempo and quarrying operations continue intermittently. The quarry exposes about 20m of strata inclined at about 20 deg. to the NW. Coarse-grained pale grey, green and dull fawn arkosic sandstones dominate the sequence but are interbedded with thin to thick pebbly sandstones and fine to coarse, matrix-supported conglomerates. Large scale examples of very low angle planar cross-laminations are evident in the west wall of the quarry overlain and underlain by parallel laminated beds. Bedding thickness varies from thin to very thick and at some levels, particularly near the top of the south face, laminae of green or purple mudstone intervene between sandstones. These mudstones do not contain miospores but are frequently associated with deep, sand-filled desiccation cracks and crude, non-directional ripples. The range of clasts that occur in conglomerates and pebbly sandstones is relatively small but is nevertheless distinctive in that they contain considerable quantities of Lower Palaeozoic greywacke and in this are quite different from both the Westphalian Drumlish Conglomerate and the Devonian Gortfinbar Conglomerate. Other clast types include abundant fawn to purple- grey trachyandesite, rare quartz and very rare pink coarse- grained granite and numerous clasts of reworked contemporaneous purple-brown mudstone, siltstone and sandstone. These are usually contained in a matrix consisting of very coarse sand mixed with angular lithic fragments. Clasts rarely exceed a diameter of 10cm in Largy Quarry although boulders over 0.3m diameter are recorded in the Ballyreagh Conglomerate. | |
| Interpretation: | |
The sedimentary rocks that constitute the three formations of the Kilskeery Group record the history of punctuated subsidence of a non-marine basin. Gradual and sustained subsidence of this basin in late Asbian times accommodated the 1000m of sand-dominated sediments of the Topped Mountain Formation. Accelerated uplift in the early Brigantian, of the southern margin of this northern land area led to increased erosion and southward progradation of alluvial fans, in the process depositing largely coarse-grained and conglomeratic debris of the Ballyreagh Formation. A gradual diminution in the rate of uplift of the metamorphic and Lower Palaeozic massif in the late Brigantian led to its eventual burial by the distal alluvial plain and playa-lake sediments of the Ballinamallard Mudstone Formation in the south, and possibly by the Greenan Sandstone in the north (Mitchell & Owens, 1990). This situation persisted into Pendleian times at which point the sedimentary record ends. | |
| Notes: | |
For information on other sites in Subarea-4 see; Key Site 1177 - Subarea-4; Fintona Block. This area is also important for Mineralogy and Metallogenesis. See Key Site 560 - Largy Hill. | |
| Keywords | |
|---|---|
| Rocks: | Conglomerate, Mudstone, Sand, Sandstone |
| Structures: | cross-bedding, dessication cracks, ripple marks |
| Access | |
|---|---|
| Approach: | 5km west of the village of Tempo. |
| References (1) | |||
|---|---|---|---|
| Blieck, A., 1991. Reappraisal of the heterostracans (agnathan vertebrates ) of Northern Ireland. Irish Journal of Earth Sciences, vol. 11 pt. 1, pp.65-69. | |||
| Map(s): | See 1:50,000 O.S. Sheet 18 (Enniskillen); GSNI (1982) 1:50,000 Solid Geology of Sheet 45 (Enniskillen). | ||
| Record type: | ESCR report | ||
| Entered by: | Doughty, P.J. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Largy Quarry, County Fermanagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=243. Accessed on 2026-11-06. |
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