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Earth Science Conservation Review
| Bannagh River | Fermanagh |
| Site number: | 231 | File Number: | H16 |
| ESCC: | EO | ||
| Locality Type: | River bank | Status: | local interest |
| Grid Reference: | H16756706,H16906750 End(s) of linear site, Not Entered | ||
| Google maps: | 54.55151,-7.74189 | ||
| County: | Fermanagh | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous | ||
| Stages: | Arundian, Visean | ||
| Lithostrat: | Drumchorick Siltstone Formation, Mullaghmore Sandstone, Tyrone Group | ||
| Site Description | |
|---|---|
| Highlights: | |
The riverbank and waterfall sections in the Mullaghmore Sandstone Formation in the Bannagh River expose a varied selection of the lithologies that comprise this formation. The contact with the succeeding Drumchorick Formation is exposed in the waterfall section. | |
| Description: | |
The section of the Bannagh River in which occur the relevant exposures of the Mullaghmore Formation extends for about 500m from a cliff exposure at H1675 6706 to the topmost waterfall (H1690 6750) at the NE end of the section. Exposures are discontinuous but demonstrate clearly the variable nature of the sedimentary rocks in this formation and, in particular, the relatively small proportion of sandstones in the sequence. The Mullaghmore Sandstone Formation consists primarily of sediments that were deposited in a deltaic environment, but there are many indications of marine conditions prevailing, at some horizons to the extent that fossiliferous limestones occur in the sequence. In any of the four main exposures (Sections A-D) that occur in this part of the Bannagh River, the facies represented by these sedimentary rocks are believed to represent shallow water, prodelta deposits. The virtual absence of channellised sandstones and of coarsening upwards sequences emphasises the distal location of this area to the sediment source and the prevalence of marine influences compared to fluvial, non-marine environments. Flooding of these intertidal bays and lagoons by the sea was a frequent occurrence and thin fossiliferous limestones or rippled very calcareous bioclastic sandstones occur commonly. The strata exposed in sections A and B are representative of these conditions. Section C contains many more examples of marine sediments but also demonstrates how fossils are often concentrated in thin beds, frequently with erosive bases and a lenticular outline. Thin channel sandstones, rippled sandstone surfaces and cross- laminations all indicate a current dominated environment with fossil debris carried into the area by storm-generated events. At the base of this section is a limestone bed 0.29m thick. This consists of coarse-grained bioclastic packstone-grainstone with abundant bioclast debris of crinoid ossicles, bryozoa, brachiopods, algae and the foraminifera Paraarchaediscus stage involutus and Viseidiscus sp. which suggest a late Arundian age. Near the base of this section are 0.9m of grey-brown micaceous mudstones and some 0.48m below their top is a single bedding surface that contains abundant remains of echinoderms. These occur as both starfish of the Subclass Asteroidea, which are rare and apparently indeterminate, and as brittle stars, which are very common, and belong to the Subclass Ophiuroidea. Specimens of the brittle stars are usually up to 0.02m diameter and although not well enough preserved for proper determination, Dr. A.B. Smith (British Museum, Natural History) believes that they belong to the genus Stephanoura, which is restricted to the late Devonian of Belgium. As far as the author is aware this is the only record of starfish and brittle stars in the Carboniferous of N. Ireland. The highest beds of the Mullaghmore Sandstone Formation in the Bannagh River are exposed in a series of waterfalls (Section D) at the NE end of the section. Lying on top of the upper falls and exposed on both banks of the river, is a bed 1.1m thick, consisting mainly of medium to dark grey calcareous sandstone, sandy limestone and bioturbated calcareous shaley sandstone. The base of this bed represents the base of the Drumchorick Siltstone Formation and strata exposed in the river east of the falls belongs to this formation. The highest beds of the Mullaghmore Sandstone Formation consist of medium to dark grey, thin bedded micaceous mudstones, siltstones and very fine-grained sandstones. DRUMCHORICK SILTSTONE FORMATION At the eastern end of this site in the Bannagh River, at H16 67 some 30m NE of the upper falls, on the north bank are mounds of rock that were dredged from the river. Much of the rock was derived from a 0.66m thick bed of dark grey silty and sandy limestone located some 2-3m above the formation base. Lithologically the bed is variably silty and shaley and varies from a fine-grained bioclastic sandy packstone to a very calcareous sandstone. The rock is intensely bioturbated and burrows including Planolites, Rhizocorallium and Thalassinoides are very common. The macrofauna is somewhat limited in composition but includes abundant, often very large, crinoid ossicles and brachiopods, in particular large examples of Linoprotonia cf. hemisphaerica and specimens of Composita cf. ficoidea and Schizophoria sp. The microbiota of this bed is limited to a few foraminifera and algae but a diverse assemblage from higher stratigraphic levels in the formation includes various species of Paraarchaediscus, Paraarchaediscus stage involutus and possibly stage concavus and Eotextularia sp. The overall composition of the foraminifera assemblage indicates a latest Arundian age for the Drumchorick Siltstone Formation. | |
| Interpretation: | |
NTERPRETATION/ | |
| Conclusions: | |
Of the many sections through various parts of the Mullaghmore Sandstone Formation in the Kesh-Omagh area the exposures in the Bannagh River provide ample examples of the lithological variability of this formation. This section emphasises the consistent marine influence on rocks in the upper part of the Mullaghmore Sandstone and demonstrates the gradational transition into the basal beds of the succeeding Drumchorick Siltstone Formation. | |
| Notes: | |
For information on other sites in Subarea-3 see; Key Site 1176 - Subarea-3; Kesh-Omagh. | |
| Keywords | |
|---|---|
| Rocks: | Mudstone, Sand, Sandstone |
| Fossil Groups: | Brachiopod, Crinoid, Echinoderm, Foraminifera, Polyzoan, Trace fossil |
| Fossil List: | Composita cf. ficoidea, Linoprotonia hemisphaerica , Paraarchaediscus stage involutus , Stephanoura sp. , Viseidiscus sp. |
| Structures: | cross-bedding, ripple marks |
| Paleoenv: | delta |
| Access | |
|---|---|
| Approach: | ~4km NNW of Kesh. |
| Record type: | ESCR report | ||
| Entered by: | Doughty, P.J. | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Bannagh River, County Fermanagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=231. Accessed on 2026-11-05. |
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