Home
Introduction
Geology of NI
Introduction to the database
ESCR site list
Map
Selected sites to visit
Additional NIEA information
Previous SiteNext Site

Earth Science Conservation Review

Summary Full report
Lisnaskea road cuttingFermanagh
Site number:206File Number:H33
ESCC:ED
Locality Type:Roadside section Status: ESCR
Grid Reference: H36213375 Centroid
Google maps: 54.25136,-7.44461
County: FermanaghCouncil area:Fermanagh & Omagh District Council
Period:Carboniferous
Stages:Visean
Lithostrat:Benbulben Shale Formation, Dartry Limestone Formation
Site Description
image: 0206a.jpg Roadside cutting at Lisnaskea, Co. Fermanagh, exposing contact between calcareous shales at top of Benbulben Shale Formation (hammer head rests on top shale bed) and overlying cherty limestones of Dartry Limestone Formation.
Roadside cutting at Lisnaskea, Co. Fermanagh, exposing contact between calcareous shales at top of Benbulben Shale Formation (hammer head rests on top shale bed) and overlying cherty limestones of Dartry Limestone Formation.
Highlights:
As far as is known this road section is the only locality in Subarea-2 that exposes the contact between the Benbulben Shale Formation and the succeeding Dartry Limestone Formation.

Description:
The road cutting is located on the southeast side of the Derrylin Road, 60m north of Balfour Castle on the west side of Lisnaskea and measures about 30m long. Some 7m of strata, dipping east at between 6-8 deg., are exposed of which the top 4.6m are the basal beds of the Dartry Limestone Formation and the remaining 2-3m represent the top beds of the Benbulben Shale Formation.

The Glencar Limestone Formation is not represented in this section or in this part of south Co. Fermanagh.

I - BENBULBEN SHALE FORMATION

Between 2 and 3m of dark grey-brown calcareous mudstones and thin limestones occur at the SW end of the cutting and represent the Benbulben Shale.
image: 0206b.jpg Detail of contact between Benbulben Shale Formation and overlying Dartry Limestone Formation (at top of ruler).
Detail of contact between Benbulben Shale Formation and overlying Dartry Limestone Formation (at top of ruler).
The top bed of this formation, beneath the lowest limestone of the Dartry Formation, comprises 0.1m of hard, calcareous, bioturbated mudstone. Macrofauna is very scarce and is restricted to occasional solitary crinoid ossicles and small brachiopods. Near the base of the section are two thin limestone beds which consist of very fine-grained spicular dolosiltstone. They contain a stunted, low diversity microbiota including the foraminifera;

Earlandia sp. lituotubellid indet. Mediocris sp. Paraarchaediscus sp. Priscella sp. Pseudoammodiscus sp. Septabrunsiina sp. Viseidiscus sp. and a single bilaminar fragment of the alga Koninckopora.

II - DARTRY LIMESTONE FORMATION

The 4.6m of strata forming the top part of the sequence in this road cutting are assigned to the Dartry Limestone Formation. They consist of interbedded thin to thick limestones and thin splintery calcareous mudstones. Bedding in the limestones is conspicuously undulose but this appears to be a compaction feature unrelated, in contrast to many other levels in this formation, to the growth of large nodules of black secondary chert. Chert, where present, takes the form of small, scattered nodules and a 0.02m bed, about 0.4m above the formation base. Lithologically the limestones are very fine-grained spicular, bioturbated packstones and lime mudstones with fish and conodont debris. The microbiota is both stunted and impoverished and, in the lowest bed of the formation, includes the following foraminifera and algae;

Archaediscus sp? Earlandia sp. Endothyra sp. Paraarchaediscus sp. Priscella sp. Pseudoammodiscus sp. Tetrataxis sp. Viseidiscus sp.

Calcisphaeres Koninckopora inflata

No macrofauna was recovered from these strata.
Interpretation:
The transitional strata between the Benbulben Shale Formation and the Dartry Limestone Formation indicate a rapid decline in the amount of mud and silt detritus reaching the basin. The virtual absence of macrofauna is a good indication of an unfavourable environment and this impression is reinforced by the stunted nature of the foraminifera and virtual absence of algae. The latter fact, coupled with the occurrence of Viseidiscus in post- Arundian sediments, is taken to indicate deposition in a relatively deep water carbonate facies with a transported microfauna and flora.

Conclusions:
In Subarea-2 the road cutting at Lisnaskea is a unique section exposing strata covering the boundary between the Benbulben Shale and Dartry Limestone formations.
Notes:


For information on other sites in Subarea-2 see;

Key Site 1175 - Subarea-2; Lisnaskea-Fivemiletown.
Keywords
Rocks:Limestone, Mudstone
Fossil Groups:Foraminifera
Fossil List:Viseidiscus sp.
Relations:Marine sediments
Measurements
Length:~30 mWidth:Height:7 m
Depth:Area:  
Access
Approach:The road cutting is located on the SE side of the Derrylin Road, 60m north of Balfour Castle on the west side of Lisnaskea.
Record type: ESCR report    
Entered by: Doughty, P.J.
 Enlander, I., Dempster, M. & Doughty, P., 2026. Lisnaskea road cutting, County Fermanagh, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=206. Accessed on 2026-11-06.

Previous SiteNext Site
Finding out more
Acknowledgments
Habitas
© National Museums NI 2003-24