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Earth Science Conservation Review
| Crockanaver Quarry, Ederny | Fermanagh |
| Site number: | 226 | File Number: | H26 |
| ESCC: | ED | ||
| Locality Type: | Quarry (disused) | Status: | ASSI |
| Grid Reference: | H223635 Centroid | ||
| Google maps: | 54.51985,-7.65562 | ||
| County: | Fermanagh | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous | ||
| Stages: | Arundian, Chadian, Visean | ||
| Lithostrat: | Ballyshannon Limestone Formation, Crockanaver Limestone Member, Tyrone Group | ||
| Site Description | |
|---|---|
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| Highlights: | |
The stratotype section in Crockanaver Quarry exposes a thick sequence of the Crockanaver Member lying above limestones and thin shales typical of the Ballyshannon Limestone Formation. The base of the member is exposed. | |
| Description: | |
Crockanaver Quarry is located at the western end of Carn ridge, in the southwestern part, and near the southern faulted margin, of the Carboniferous outcrop in the Kesh-Omagh area. Located between the Cool and Castle Archdale faults (1:50,000 Sheets 32 and 33) the Ballyshannon Limestone crops out over the largest part of this area and is well exposed in many quarries. Crockanaver Quarry exposes about 20m of strata near the top of the Ballyshannon Formation. The highest beds, which belong to the Ederny Limestone Member, crop out in low rock ridges south of the farm road that fringes the southern margin of the quarry, and do not occur in this quarry. The contact between this member and the top of the underlying Crockanaver Limestone Member is concealed. The lowest 12m of strata in the quarry are thin to very thick dark grey medium-grained crinoidal packstones, variably argillaceous, that are interbedded with and merge gradationally into earthy shales and shaley siltstones usually up to 0.1m thick but, at the base of the quarry in the northeast corner, attaining a thickness of 0.6m. Fossils occur sporadically throughout these strata, in particular brachiopods, including rare specimens of Delepinea carinata, indicating a mid-Arundian age, and occasional colonies of the coral Siphonodendron martini. In the Ballyshannon Limestone Formation in the Kesh-Omagh area, the occurrence of chert is restricted to one thin section near the top of the formation. In Crockanaver Quarry nodules and discontinuous layers of blue-black chert  The Crockanaver Limestone Member is not more than 10m thick and consists of thin to thick beds of medium fawn to pale grey crinoidal grainstones with no shales. Fossils are invariably fragmented and all fragments are usually micritised. The one exception to this is the brachiopod Composita ambigua which occurs commonly as unbroken specimens with both valves conjoined. Corals do not occur in the member. In the stratotype quarry the contact between the base of the Crockanaver Member and the underlying dark grey packstones with shales is very sharp.  | |
| Interpretation: | |
Coarse, shale-free, grainstones such as the Crockanaver Limestone Member are believed to indicate deposition of lime sand in shallow, agitated water. The presence of strong currents is responsible for winnowing-out all fine-grained lime mud or terriginous muds, leaving behind only the coarsest particles of carbonate debris and, more rarely quartz grains. The carbonate sand is loosely packed and individual grains are cemented together by coarse calcite spar. The lenticular shape of individual outcrops of the Crockanaver Member, and its discontinuous outcrop pattern, suggests that shallowing of the sea bed was not a universal feature of the basin at this time. The grainstones probably developed as shallow water, submarine, carbonate sand banks on what was still a very shallow water and widespread platform at that time in much of NW Ireland. | |
| Conclusions: | |
Crockanaver Quarry is the stratotype section for the Crockanaver Limestone Member of the Ballyshannon Limestone Formation. | |
| Notes: | |
For information on other sites in Subarea-3 see; Key Site 1176 - Subarea-3; Kesh-Omagh. | |
| Keywords | |
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| Rocks: | Crinoidal limestone, Limestone |
| Fossil Groups: | Brachiopod, Coral |
| Relations: | Marine sediments |
| Access | |
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| Approach: | 1.5km south of Ederny. |
| Map(s): | GSNI 1:50,000 Solid Geology Sheets 32 & 33. | ||
| Record type: | ESCR report | ||
| Entered by: | Doughty, P.J. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Crockanaver Quarry, Ederny, County Fermanagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=226. Accessed on 2026-11-06. |
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