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Earth Science Conservation Review
| Benburb | Tyrone |
| Site number: | 8 | File Number: | H85 |
| ESCC: | EO | ||
| Locality Type: | Stream section | Status: | ASSI |
| Grid Reference: | H810521 Approximate | ||
| Google maps: | 54.41149,-6.75244 | ||
| County: | Tyrone | Council area: | Mid Ulster District Council |
| Period: | Quaternary | ||
| Stages: | Gortian, Pleistocene | ||
| Site Description | |
|---|---|
| Highlights: | |
The interglacial peat deposit at Benburb is sealed by glacigenic diamict. It is the only interglacial peat deposit known at present in Northern Ireland (Boulter and Mitchell, 1977; Gennard, 1984). Floristically its pollen content is similar to about ten other interglacial sites in Ireland which are thought to belong to the Gortian temperate stage (Coxon, 1993). It contains the protocratic, early and late temperate stages of this interglacial cycle. Floristic studies of the sequence highlight many of the problems involved in the correlations between interglacial sequences in Ireland and those in England. | |
| Introduction: | |
The original exposures of the interglacial peat were discovered in the bank of a small tributary of the River Blackwater about 500m southwest of Benburb village (Boulter and Micthell, 1977). Two farther exposures were located in the immediate vicinity with exposures of 13m on the west bank of the tributary stream. The peat extended to at least 2.1m below the river bed (Gennard, 1984). Originally Boulter and Mitchell (1977) suggested that the peat was overlain by a boulder clay which was deposited during the final stages of the Late Midlandian glaciation. Gennard (1986) suggested that the peat occurs stratigraphically below the local drumlin fields and probably was more extensive prior to drumlin formation. The peat is compressed and the lack of firm stratigraphic control and poor exposures does not rule out the possibility that the peat is not in situ. | |
| Description: | |
The lithological variations described from the Benburb sequence are based on core B which was obtained by percussion drilling. The resulting pollen diagrams were constructed using the numerical zonation programme developed by Gordon and Birks (1972). It does not confine the date to any preconceived pattern of plant succession. The zonation was as follows: PAZ 0, 4.15- 3.95m; PAZ 1, 3.95- 3.60m; PAZ 2, 3.60-3.50m; PAZ 3, 3.50-3.25m; PAZ 4, 3.25-2.75m. PAZ 1 From level 3.84m the greatest contributors are Pinus (>80%) and Betula (<10%). Alnus, Salix, Juniperus and Coryloid pollen are also present. Non-aboreal pollen include Gramineae (<50%), Cyperaceae (<10%), aquatics and members of a rich herbaceous flora. PAZ 2 This zone comprises only three spectra. Pinus and Taxus pollen are strongly represented. Alnus levels rise to 36% and Gramineae falls to 10%. Levels of Coryloid pollen rise to a peak of 10% and Betula falls to below 5%. Fraxinus and Ulmus are present is small quantities. PAZ 3 Pinus pollen falls from 25% to around 15% and the wet-land vegetation is supplemented by mixed deciduous forest comprising Quercus, Fraxinus and Ulmus. Fagus grains were recorded only at this level. Hedera and Ilex are also present. PAZ 4A Abies pollen enters the diagram for the first time and suggests that the vegetation surrounding the area was predominantly Abies forest. Rhododendron and species X also are distinctive fossils at this level. PAZ 4B Abies falls away despite a peak at levels 2.88m and 2.92m, as does Alnus and Coryloid pollen, leaving Taxus as the dominant arboreal species. Picea which is present throughout the diagram in small quantities, rises to a maximum in this zone. However a return of Pinus and Betula is not marked and they do not comprise the dominant arboreal species at the top of the sequence. To some extent this apparent absence may be a reflection of low pollen concentrations. Macrofossil analysis showed that Najas flexilis Rostk and Schmidt is the most abundant species found in PAZ 0 and it is circumboreal in distribution. The majority of seeds recovered from PAZ 0 are from submerged or floating aquatics. The presence of land plants around the pond is indicated by the fruits of Alnus, Betula pubescens Ehrh and Betula pendula Roth. B. pendula during PAZ 1. In PAZ 2 seeds of Erica ciliris L and leaves of Sphagnum were found. Most of the remains represent the local flora of the water edge. In PAZ 3 macrofossils of Sphagnum occur together with Alnus glutinosa Gaertn. fruit. In PAZ 4 leaves of Abies alba are typically present. Gennard (1984) concludes from the carbonate levels (5-8%) that the peat has not been leached and is sealed by two clay units. It is also suggested that the lack of clear bedding planes and the fairly uniform nature of the peat suggests that nonconformities are absent (Gennard, 1984). | |
| Importance: | |
The peat stratigraphy at Benburb is sealed by a glacial till and as such is the only interglacial record known in Northern Ireland. It is therefore of national importance as a stratigraphic type site. On a wider front it should play a critical role in the formulation of geological concepts concerning the interpretations of floristic differences within interglacial sequences. | |
| Interpretation: | |
The independent pollen zonation (PAZ 1 - 4) confirms that the Benburb sequence is the first interglacial to be recorded in the north of Ireland (Gennard, 1984). The core represents three stages of the interglacial - the protocratic stage and the Early and Late Temperate stages. The basic pollen assemblages are similar to those of Gortian sites elsewhere in Ireland (Coxon, 1993) and include the association of Abies, Taxus, species X and Rhododendron in the late temperate stage. However certain differences exist between the assemblages at Benburb and other Gortian sites in Ireland (Gennard, 1984; Coxon, 1994). In PAZ 1 levels of Hippophae are low at Benburb but it can hardly be considered as an indicator of a specific interglacial (Godwin, 1978). Coryloid pollen is found early in PAZ 1 at Benburb but enters the profile in association with Quercus and Hedera (Jessen et al., 1959; Watts, 1959) at Gort and Baggotstown. Statistically Ulmus levels at Benburb are greater than those found at Gortian sites. Buxus pollen occurs exclusively in the mixed deciduous forest assemblage at Benburb, and is not found in association with the zone dominanted by Abies as is typical of other Gortian sites. Finally Azolla filiculoides which is often used to characterize interglacials prior to the last interglacial is absent form Benburb. The differences between the Benburb assemblages and other Gortian sites may be interpreted in several ways. Differences in their floristic composition may reflect a geographic variation within the same interglacial. A similar variation is known to exist within the postglacial (Birks et al., 1975). Here geographic spectra based on levels of Pinus, Betula, Quercus, Ulmus, Alnus, Corylus and Tilia prior to 5,000 B.P. divided western Ireland, and eastern/northern Scotland from the rest of Britain. Alternatively it could be argued that the presence of only one till above the interglacial peats suggests a last interglacial age even though the critical stratigraphic marker of Carpinus pollen is not present. | |
| Conclusions: | |
The peaty sequence at Benburb is sealed by a drumlin farming till and therefore predates the last cold stage. The four major pollen assemblage zones are representative of an interglacial cycle though the final telocratic phase has been truncated or is a non-sequence. Pollen assemblages and marker taxa from Benburb are fairly similar to Gortian sites elsewhere in Ireland and suggest a penultiminate interglacial age. Floristic differences between Benburb and other Gortian sites may well reflect geographic variability in floristic composition within the same interglacial. | |
| Notes: | |
Most of the peat is sealed beneath a few metres of glacial till and is only partly exposed along the banks of the tributary stream. The boundary drawn cannot predict the true subsurface extent of the peats. | |
| Keywords | |
|---|---|
| Fossil Groups: | Plant |
| Relations: | Interglacial deposit |
| Geomorph: | interglacial peat, pollen analysis, till |
| Paleoenv: | lacustrine |
| Measurements | |||||
|---|---|---|---|---|---|
| Length: | 13 m | Width: | Height: | ||
| Depth: | Area: | ||||
| Access | |
|---|---|
| Approach: | Just off the lane leading to Benburb weaving factory. |
| Management: | |
As the interglacial peat is mainly buried farming activities will not influence or damage the site. Possibly the site could be best preserved if it was simply left without any active management policy. However any deep excavations or extension of the factory area would damage the scientific potential of the site. The site can withstand reasonable scientific investigation. Notifiable operations therefore include: 1: Disturbance/modification of the land surface, subsurface, water levels or water courses. Whether by engineering works, drainage works or spreading/dumping/storage of materials. 2: Field drainage or field boundary change. 3: Use of machinery likely to damage existing exposures. 4: Any extraction, e.g deepening of drains. 5: Afforestation or tree planting. 6: Dumping, spreading, discharge or storage of any materials. | |
| Threats: | Deep excavations; extensions to the factory area. |
| Uses | |
| Uses: | The surrounding fields are used mainly for silage and grazing. A factory is sited near the exit of the small stream on the north bank of the Blackwater river. |
| References (6) | |||
|---|---|---|---|
| Birks, H.J.B., Decon, J. & Peglar, S., 1975. Pollen maps for the British Isles 5000 years ago. Proceedings of the Royal Society, London, vol. B189, pp.87-105. | |||
| Boulter, N. & Mitchell, W.I., 1977. Middle Pleistocene (Gortian) deposits from Benburb, Northern Ireland. Irish Naturalists Journal, vol. 19, pp.2-3. | |||
| Coxon, p., 1993. Irish Pleistocene biostratigraphy. Irish Journal of Earth Sciences, vol. 12, pp.83-105. | |||
| Gordon, A.D. & Birks, H.J.B., 1972. Numerical methods in Quaternary palaeoecology. New Phytologist, vol. 71, pp.961-976. | |||
| Jessen, K., Anderson, S.T. & Farrington, A., 1959. The interglacial deposit near Gort, Co. Galway, Ireland. Proceedings of the Royal Irish Academy, vol. 60B, pp.3-77. | |||
| Watts, W.A., 1959. Interglacial deposits at Kilbeg and Newtown, Co. Waterford. Proceedings of the Royal Irish Academy, vol. 60B, pp.79-134. | |||
| Map(s): | See the 1:50,000 O.S. Sheet 19 (Armagh). | ||
| Record type: | Environment Serv. GIS, ESCR report | ||
| Entered by: | Crowther, P.R. | ||
| Last updated: | 23 Dec 2003 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Benburb, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=8. Accessed on 2026-11-05. |
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