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Earth Science Conservation Review
| Plaister Quarry, Aughnacloy | Tyrone |
| Site number: | 256 | File Number: | H65 |
| ESCC: | ED | ||
| Locality Type: | Quarry (disused) | Status: | local interest |
| Grid Reference: | H678539 Centroid | ||
| Google maps: | 54.42958,-6.95529 | ||
| County: | Tyrone | Council area: | Mid Ulster District Council |
| Period: | Carboniferous | ||
| Stages: | Visean | ||
| Lithostrat: | Maydown Limestone Formation, Tyrone Group | ||
| Site Description | |
|---|---|
| Highlights: | |
Plaister Quarry exposes a small thickness of highly bioclastic limestones and thin splintery shales that are typical of the upper part of the Maydown Limestone Formation. A prolific fauna dominated by corals and brachiopods is of Asbian age. | |
| Description: | |
Plaister Quarry (H676 539) is located 2.25km NNE of the centre of Aughnacloy, in the eponymous townland. The strata in the quarry were equated, on the 1:50,000 geological map of the Clogher area (Sheet 46, 1983), with the Dartry Limestone Formation. This correlation is not correct as that formation is never as profusely fossiliferous as the lithologies found in this quarry. A better correlation would have been with the Glencar Limestone Formation which is similarly fossiliferous, but in a regional context, and given the variability of other Asbian lithologies in the Aughnacloy-Tynan area, the author believes that these strata are better assigned to the Maydown Limestone Formation. About 8m of interbedded limestones and silty shales inclined north-northwestwards at 20 deg. are exposed in the quarry. Limestones, which occur in beds between 0.1-0.5m thick and consist of blue-grey, very fossiliferous crinoidal packstones, are characteristically undulose. They are separated by dark grey-brown earthy shaley siltstones, with thin lenticular and nodular limestones, up to 0.2m thick. All lithologies are extremely fossiliferous and the following corals occur commonly: Dibunophyllum sp. Diphyphyllum sp. Hexaphyllia aff. mirabilis Lithostrotion portlocki Siphonodendron martini S. pauciradiale Siphonophyllia benburbensis Syringopora cf. ramulosa The occurrence of such a prolific coral fauna that includes S. pauciradiale and S. benburbensis is quite typical of the Maydown Limestone and is Asbian. Brachiopods also occur commonly and include the following forms: Alitaria panderi Antiquatonia aff. insculpta Buxtonia sp. Dielasma sp. Echinoconchus subelegans Gigantoproductus tulensis Krotovia spinulosa Leptagonia analoga Linoproductus sp. hemisphaericus group Plicochonetes sp. Productina margaritacea Schizophoria sp. Spirifer bisulcatus Spiriferellina octoplicata This association of brachiopods is very reminiscent of that in the Glencar Limestone Formation. Many of the taxa are common in reef facies assemblages but the important species is G. tulensis, whose stratigraphic range is restricted to the early Asbian. The macrofauna also includes a variety of bivalves, bryozoa, gastropods and trilobites. | |
| Interpretation: | |
The Asbian, probably early Asbian, age of the strata exposed in Plaister Quarry is demonstrated by elements of the prolific coral-brachiopod fauna that occurs there. Such an assemblage is quite atypical of the Dartry Limestone Formation, to which the rocks were attributed by the GSNI (1983), but very closely resembles, and is clearly equivalent both in terms of its age and its composition, that found in the Glencar Limestone Formation. Based on the very well exposed sequence at Benburb it is evident that lithologies typical of the Dartry Formation are not developed either there, or in the Aughnacloy-Tynan area. In view of the transitional nature of the shale-limestone lithologies and their relative proportions it was decided to incorporate all of them in the Maydown Limestone Formation, of early Asbian age, and the author believes that the strata exposed in Plaister Quarry represent the upper part of this formation. | |
| Conclusions: | |
Plaister Quarry represents a clean, shallow exposure of very fossiliferous limestones and shales of the Maydown Limestone Formation. Abundant fossils indicate an early Asbian age for the strata. | |
| Notes: | |
For information on other sites in Subarea-5 see; Key Site 1178 - Subarea-5; Clogher-Aughnacloy. | |
| Keywords | |
|---|---|
| Rocks: | Crinoidal limestone, Limestone |
| Fossil Groups: | Bivalve, Brachiopod, Coral, Gastropod, Polyzoan, Trilobite |
| Fossil List: | Gigantoproductus tulensis, Siphonodendron pauciradiale , Siphonophyllia benburbensis |
| Relations: | Marine sediments |
| Access | |
|---|---|
| Approach: | 2.25km NNE of the centre of Aughnacloy. |
| References (2) | |||
|---|---|---|---|
| Egan, F.W., 1873. Explanatory memoir to accompany Sheet 47 of the maps of the Geological Survey of Ireland, including the country around Armagh. Memoirs of the Geological Survey of Ireland, Dublin. | |||
| Mitchell, W.I. & Mitchell, M., 1982. The Lower Carboniferous (Upper Visean) succession at Benburb, Northern Ireland. Report of the Institute of Geological Sciences, numb. 82/12. | |||
| Record type: | ESCR report | ||
| Entered by: | Doughty, P.J. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Plaister Quarry, Aughnacloy, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=256. Accessed on 2026-11-08. |
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