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Earth Science Conservation Review
| Keenaghan Lough - Carboniferous | Fermanagh |
| Site number: | 218 | File Number: | G95 |
| ESCC: | EO | ||
| Locality Type: | Inland exposure | Status: | ESCR |
| Grid Reference: | G97305999 Centroid | ||
| Google maps: | 54.488,-8.04164 | ||
| County: | Fermanagh | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous | ||
| Stages: | Visean | ||
| Lithostrat: | Keenaghan Shale Formation, Tyrone Group | ||
| Site Description | |
|---|---|
| Highlights: | |
The exposure reveals the plane of unconformity between the Keenaghan Shale Formation and the Lough Derg Group. | |
| Description: | |
The Keenaghan Shale Formation is very badly exposed within its area of outcrop on the shores of Keenaghan Lough and Lough Scolban (GSNI, 1994, 1:50,000 Sheet 32). It consists of about 20m of micaceous black shales, silty shales, thin and lenticular beds of coarse-grained, calcareous, grey sandstone, thin beds of laminated algal (cyanobacterial) limestone and of unlaminated micrites. One of the better outcrops, which exposes clearly the sub- Carboniferous unconformity, occurs on the shore of Keenaghan Lough at its NW corner. Strata at this locality are inclined southwards at 20 deg. and include, in particular a bedding surface on a layer of laminated carbonates bearing well preserved desiccation cracks. The infill of the cracks and the enclosing lithologies consist of dark grey carbonaceous shale. A temporary excavation behind the cottage, located 450m east of this locality exposed soft black shales and silty shales. Palynological analysis of the shales identified a limited miospore population that included the following forms: Auroraspora macra Calamospora spp. Lycospora pusilla (rare) Prolycospora rugulosa (common) Punctatisporties spp. Retusotriletes spp. Rugospora minuta Spelaeotriletes spp. S. cf. pretiosus The occurrence of Lycospora pusilla in early Carboniferous assemblages is taken to indicate a Vis‚an age. In this instance the relative scarcity of that miospore species and the abundance of Prolycospora rugulosa certainly indicates an assignment to the Pu Biozone, and a possible early Chadian (late Tournaisian) age. | |
| Interpretation: | |
The assignment of an early Chadian age to the Keenaghan Shale Formation is still not satisfactorily proven. However in view of the occurrence of Waulsortian mudmounds (Magherameena Member) at the base of the succeeding Ballyshannon Limestone Formation it is likely that this dating is correct although no corroborating evidence has yet been found in the mudmounds. Nevertheless the sedimentary rocks of the Keenaghan Shale belong to the sabkha facies and illustrate that sedimentation, in late Tournaisian - early Vis‚an times commenced only just before the arrival of the main Vis‚an marine transgression. In the Enniskillen area of Subarea-1, over 30km SE of Keenaghan Lough, similar Waulsortian mudmounds are underlain by a very thick marine and peritidal sequence. | |
| Conclusions: | |
The 'basal clastic' Keenaghan Shale Formation is exposed on the north shore of Keenaghan Lough. The contrast between these strata and the Omagh Sandstone Group and Claragh Sandstone Formation, east of the Pettigoe Fault is enormous and testifies to very different palaeogeographic histories in the two areas. | |
| Notes: | |
For information on other sites in Subarea-3 see; Key Site 1176 - Subarea-3; Kesh-Omagh. This area is also important for Mineralogy and Metallogenesis. See Key Site 543 - Keenaghan, on Belleek-Kesh road. | |
| Keywords | |
|---|---|
| Rocks: | Sand, Sandstone, Shale |
| Fossil Groups: | Miospore |
| Measurements | |||||
|---|---|---|---|---|---|
| Length: | 20 m | Width: | Height: | ||
| Depth: | Area: | ||||
| Map(s): | GSNI (1994) 1:50,000 Solid Geology Sheet 32. | ||
| Record type: | ESCR report | ||
| Entered by: | Crowther, P.R. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Keenaghan Lough - Carboniferous, County Fermanagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=218. Accessed on 2026-11-06. |
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