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Earth Science Conservation Review
| Tullyconnell | Tyrone |
| Site number: | 121 | ||
| ESCC: | EO | ||
| Locality Type: | Subcrop | Status: | ESCR |
| Grid Reference: | H844747 Centroid | ||
| Google maps: | 54.6139,-6.69363 | ||
| County: | Tyrone | Council area: | Mid Ulster District Council |
| Period: | Permian | ||
| Stages: | Upper Permian | ||
| Lithostrat: | Magnesian Limestone | ||
| Site Description | |
|---|---|
| Highlights: | |
The Magnesian Limestone in the area around Grange, Co. Tyrone attains its maximum thickness in Northern Ireland and is the most westerly outcrop of marine Permian strata in Europe. Fossils are significantly more abundant, diverse and better preserved than from outcrops elsewhere in the province. | |
| Introduction: | |
Dolomitic yellow limestones yielding late Permian fossils formerly were exposed at the village of Grange, five km SE of Dungannon, Co. Tyrone. More recently, fragments of the same limestone were recovered from revegetated excavations in the townland of Tullyconnell, one km to the east (Grid ref. H/844747). The outcrop of the limestone was mapped by Portlock (1843) but mistaken for Carboniferous sandstone. Subsequently it was described in some detail by King (1856), who was the first to note the occurrence of Permian rocks in this area. It was mentioned again by Hardman (1877). The only significant accounts published this century are those by Fowler (1955) and Fowler and Robbie (1961), describing the succession in a series of five boreholes, and by Pattison (1970), who reviewed the late Permian marine fauna from Northern Ireland and north-west England. | |
| Description: | |
Other than the foreshore outcrop at Cultra, the outcrop of Magnesian Limestone at Tullyconnell is the only area in Northern Ireland from which Permian marine fossils have been obtained and, of the two sites, it has yielded a significantly richer and more diverse fauna. Professor William King described the limestone at Tullyconnell as "chemically and lithologically the same as much of the Magnesian Limestone in the county of Durham", also stating that "the same may be said of the Cultra 'fossiliferous dolomite'" (King 1856). King identified 13 fossil species from the Magnesian Limestone at Tullyconnell, giving brief descriptions and illustrations of each of these. King described at some length the field evidence for ascertaining the outcrop of Permian strata in this area and their relationship to strata above and below. Exposures at that time, although much more extensive than at the present day, evidently were rather limited and so the exact relationship between the various strata remained uncertain. He concluded that the Magnesian Limestone was overlain, at no great distance, by 'New Red Sandstone'. This sandstone was worked for building stone in a quarry about a mile to the north, near Ardtrea; this implies that the red sandstone probably is the Sherwood Sandstone rather than a representative of the Connswater Marls which also are predominantly red but are not suitable for building stone. Northeastward dipping Carboniferous Limestone was exposed about a mile to the south of the Magnesian Limestone but he concluded that the Coal Measures were absent, either through pre-Permian erosion or cut out by a major fault running through Tullyconnell Hill. This basic sequence, with Carboniferous Limestone overlain unconformably by the Permian succession, which in turn is succeeded conformably by Triassic sandstones, has been confirmed in all of the boreholes described by Fowler (1955) and Fowler and Robbie (1961). King's (1856) description of the outcrop appears to have been hampered by the short time he had at the site. The subsequent geological survey of the locality by Hardman (1877) allowed him to describe the deposit in greater detail. The Permian rocks were "best seen in a short section under the bank of the road leading to Ardtrea, townland of Tullyconnell, the whole extending for only 48 feet". The limestone was said to consist of a few alternations of yellow, reddish or variegated dolomitic limestones, some with a sandy texture. Fossils were abundant in both the uppermost and lowermost beds. However, by the time it was described by Fowler (1955) the exposure was much degraded and confined to fragments on the surface of the grassed-over diggings and a few angular boulders and fragments on the bank of the nearby stream. The fullest description of the Permian succession in this area was obtained from five boreholes sunk to the east of Grange between 1948 and 1955 and described by Fowler (1955) and Fowler and Robbie (1961). Thickness of the Magnesian Limestone in the three boreholes varied from 18.3 metres to 23.2 metres (59.5 feet to 75.5 feet). In all of the boreholes the Magnesian Limestone was underlain by 0.1-7.7 metres of dull brownish-red sands lying unconformably upon Carboniferous Limestone. The Magnesian Limestone is overlain by red sandstones or evaporitic siltstones of presumed Permian age, passing up into several hundred metres of Triassic Sherwood Sandstone and, in the case of the Mullaghglass Borehole, a substantial thickness of the Mercia Mudstone Group preserved above this. Fowler (1955) and Fowler and Robbie (1961) described the Magnesian Limestone as a calcareous dolomitic limestone, predominantly yellow or cream in colour but occasionally grey or pink. Typically it is fine to medium grained but may be quite coarse grained where oolitic and porous. Quartz pebbles and grains occur scattered throughout the entire thickness of the limestone. The area was visited in June 1998 and again in March 1999. The only exposure located was that on the east bank of the Killymoon River near Tullyhogue (Grid ref. H/823750). Patchy exposures over about a 15 metre stretch of riverbank at the foot of a drumlin expose a total thickness of about 2 metres of thinly-bedded, but apparently unfossiliferous, saccharoidal dolomite. However, fossiliferous fragments of Magnesian Limestone were found in surface brash at several locations around Tullyconnell Hill and indicate that the main outcrop here lies at very shallow depth below the drift cover. Pattison (1970) recognised four distinct types of fossil assemblage in the boreholes of the Grange area. The most diverse assemblage (Type D) included bryozoa as well as gastropods and bivalves while the most impoverished (Type A) was dominated by Bakevellia binneyi with only a few other bivalves and rare gastropods. He was able to recognise a sequence of relative abundance within the common bivalve genera, which he equated to decreasing tolerance of adverse conditions, the sequence running as follows; Bakevellia - Schizodus - Permophorus - Liebea - Pseudomonotis and/or Parallelodon. Fossils were present throughout most of the thickness of the Magnesian Limestone but a variable thickness of unfossiliferous limestone was seen in each of the boreholes, typically from 10 to 15 metres above the base. The rich fauna obtained from the boreholes was identified by C.J.Stubblefield and subsequently was re-examined by Pattison (1970). He noted that, by comparison with the Magnesian Limestone of north-east England, there were relatively few species represented and they were of smaller average size. Specimens reported by King (1855) but not subsequently confirmed by Pattison (1970) are denoted with an asterisk. ANTHOZOA * 'Favosites' mackrothii Geinitz BRYOZOA Bryozoa locally are common but most are fragmented and difficult to determine to generic level. Batostomella columnaris (Schlotheim), Batostomella ?crassa (Lonsdale), Thamniscus dubius (Schlotheim) MOLLUSCA - BIVALVIA Bakevillia (Bakevillia) binneyi (Brown), Bakevillia (Bakevillia) ceratophaga (Schlotheim), cf. Elimata permiana (King), Liebea squamosa (J. de C.Sowerby), Permophorus costatus (Brown), cf. Pseudomonotis sp., Schizodus obscurus (J.Sowerby) MOLLUSCA - GASTROPODA Gastropods make up a significant proportion of the fauna of the Magnesian Limestone of this area but invariably are preserved only as internal or external moulds and many cannot be identified to generic level: * Coelostylina ? leighi (Brown), Coelostylina ?obtusa (Brown), Glyptospira ?helicina (Schlotheim), Glyptospira ?tunstallensis (King), cf. Mourlonia ?antrina Schlotheim, cf. Naticopsis minima (Brown), cf. 'Rissoa' altenburgensis (Geinitz) ARTHROPODA - OSTRACODA Very few ostracods have been seen and all are small, commonly crushed and preserved as internal moulds. Identifications are, at best, tentative: Carbonita ?tumida Kellett, ?Kirkbya permiana King FORAMINIFERA Agathammina pusilla (Geinitz), * ?Agathammina milioloides (Jones, Parker and Kirkby), Calcitornella ?minutissima (Howse), cf. Cyclogyra sp., cf. Hemigordius ? sp. THALLOPHYTA Filograna ?permiana King; recorded by Fowler (1955) but considered doubtful by Pattison (1970) | |
| Importance: | |
The Magnesian Limestone at Tullyconnell is important as one of only two fossiliferous Permian outcrops in Northern Ireland, and indeed Ireland as a whole. Although the outcrop at Cultra is much better exposed, the fauna obtained from Tullyconnell is more diverse and better preserved, allowing more meaningful comparison and correlation with the classic Permian succession of north-east England. In terms of its international significance, the locality represents the most westerly outcrop of the Magnesian Limestone and its correlatives in Europe. An understanding of the fauna, and the possible controls on its diversity, is critical to any interpretation of the extent and effects of late Permian marine transgressions. | |
| Interpretation: | |
King (1856) clearly was correct in correlating the fauna at Tullyconnell with that of the Magnesian Limestone of north-east England but his precise correlation with the Upper Magnesian Limestone has not gone unchallenged. The identity of the fossils he found, taken in conjunction with the chemical and lithological similarities already alluded to, led him to conclude that the Tullyconnell and Cultra outcrops of Magnesian Limestone could be correlated with the "first member [Upper Magnesian Limestone] as it occurs in Durham". Only five years later Kirkby (1861) disputed this, regarding the fauna as more indicative of correlation with the Lower Limestone of south Yorkshire. Fowler (1955), however, considered the absence of brachiopods from the fauna at Tullyconnell and Cultra, and the presence of evaporites immediately above the Magnesian Limestone in two of the boreholes, to indicate a correlation with the Upper Magnesian Limestone of north-east England, as originally proposed by King (1855), although noting the difficulties of correlation over the considerable distance between this outcrop and north-east England. Pattison (1970) further discussed the difficulties of correlating the Magnesian Limestone of Northern Ireland with that of north-east England and the Zechstein Cycles of northern Germany. These difficulties arise mainly from the preponderance of facies dependent fossils and the relatively long stratigraphic ranges of many of the common taxa. Nonetheless, he was able to conclude that the Magnesian Limestone of Co. Tyrone can be correlated with the carbonate phase of either the Z1 or Z2 cycles, or possibly both, but almost certainly does not correlate with Z3. This view is maintained in the most recent correlation (Smith et al. 1974) which places the Magnesian Limestone of Co. Tyrone and Cultra as early Upper Permian in age on the basis of overall lithological character and the sparse bivalve and gastropod fauna. Hence it can be correlated with the Lower, or possibly Middle, Magnesian Limestone of the Durham region. The consistent presence of an unfossiliferous gap within the Magnesian Limestone of Co. Tyrone has been taken as evidence for correlating the Magnesian Limestone of Co. Tyrone with more than one of the Zechstein/ Magnesian Limestone cycles of Northern Germany and north-east England (Stubblefield in Fowler 1955). Pattison's (1970) detailed study concluded that the fauna of the 'Bakevellia Sea', which extended west of the Pennines across into Northern Ireland, was comparable with that of near-shore carbonates in the first cycle of the English 'Zechstein Sea', which extended to the east of the Pennines. However, field evidence suggests that the marine Permian carbonates west of the Pennines were deposited in several discrete basins, one of these being located in Co. Tyrone. This basin must at some point have been linked with the Zechstein Sea but Pattison (1970) suggested that this was not a direct east-west link but more probably was via a channel extending north. The low diversity of the fauna in Northern Ireland, in particular the absence of echinoderms or cephalopods and the virtual absence of brachiopods (they are known only from Cultra), and the small size of individual taxa when compared with material from north-east England, was attributed by Pattison (1970) to adverse conditions associated with the tenuous link between the 'Bakevellia Sea' and the open ocean. More specifically this can be ascribed to unfavourable salinity levels, either hypersaline or hyposaline depending on the relative contributions from evaporation and from runoff from adjacent landmasses. The more diverse assemblages, in which bryozoa are a significant element, presumably relate to periods when salinity approached more closely to fully marine while increasing hyper- or hypo-salinity reduced faunal diversity or even eliminated preservable elements of the fauna altogether. Of all elements of the fauna, the bivalve Bakevellia seems to have been the most successful opportunist since it occurs not only where other fossils are absent but also forms the commonest component of the more diverse assemblages. | |
| Conclusions: | |
The Magnesian Limestone at Tullyconnell represents the most westerly outcrop of marine Permian rocks in Europe. The Magnesian Limestone in Co. Tyrone has yielded a more diverse and better preserved fauna than that from Cultra further to the east. The limestone and its fauna have significant implications for correlation with successions in north-east England and Northern Germany and for the reconstruction of the former extent of the Zechstein Sea. | |
| Notes: | |
For general information and references on the Palaeontology of Northern Ireland see Key Site 109 - Palaeontological sites of N. Ireland - Introduction For other site specific information and references on the Palaeontology of Northern Ireland see Key Site 110 - Ballycastle Pellet Chalk, Key Site 111 - Ballypalady Plant Bed, Key Site 112 - Carrick Lough, Bunnahone Lough and the Sillees River, Key Site 113 - Faragandoo, Key Site 114 - Minnis North Mudflow, Key Site 115 - Moyola River, Key Site 116 - Mullynaskeagh Clay Pit, Key Site 117 - Murlough Bay, Key Site 118 - Portnaloub, Key Site 119 - Sillees River, Glenasheevar, and Key Site 120 - Tircrevan Burn (palaeontology). | |
| Keywords | |
|---|---|
| Rocks: | Dolomite |
| Fossil Groups: | Arthropod, Bivalve, Coral, Foraminifera, Gastropod, Polyzoan |
| Access | |
|---|---|
| Management: | |
In the absence of any exposure at present no management plan can be instigated. However, since the Magnesian Limestone evidently lies at such a shallow depth in this area it may well be re-exposed during agricultural or building development, at which time appropriate steps will need to be taken to ensure a section is retained in some form. | |
| Uses | |
| Uses: | The land around the Permian outcrop at Tullyconnell is largely agricultural in its present use. Most is under pasture for cattle grazing but some arable is present on the lower ground. |
| References (8) | |||
|---|---|---|---|
| Fowler, A., 1955. The Permian of Grange, County Tyrone. Bulletins of the Geological Survey of Great Britain, vol. 8, pp.44-53. | |||
| Fowler, A. & Robbie, J.A., 1961. Geology of the country around Dungannon. Memoirs of the Geological Survey Northern Ireland, HMSO, Belfast. | |||
| Hardman, E.T., 1877. On the geology of the Tyrone coal-field and surrounding districts Memoirs of the Geological Survey of Ireland. | |||
| King, W., 1856. On the occurrence of Permian Magnesian Limestone at Tullyconnel, near Ardtrea, in the county of Tyrone Journal of the Geological Society of Dublin, vol. 3, pp.67-81. | |||
| Kirkby, J.W., 1861. On the Permian rocks of south Yorkshire; and on their palaeontological relations Quarterly Journal of the Geological Society of London, vol. 17, pp.287-325. | |||
| Manning, P.I., Robbie, J.A. & Fowler, A., 1970. Geology of Belfast and the Lagan Valley Memoirs of the Geological Survey Northern Ireland, vol. 36. | |||
| Pattison, J., 1970. A review of marine fossils from the Upper Permian rock of Northern Ireland and north-west England. Bulletins of the Geological Survey of Great Britain, vol. 32, pp.123-165. | |||
| Smith, D.B., Brunstom, R.G.W., Manning, P.I., Simpson, S. & Shotton, F.W., 1974. A correlation of Permian rocks in the British Isles. Journal of the Geological Society of London, vol. 130, pp.1-45. | |||
| Record type: | ESCR report | Recorded by: | Michael J. Simms, Department of Geology, Ulster Mu |
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Tullyconnell, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=121. Accessed on 2026-11-08. |
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