ESCR - Ballykelly, Sistrakeel and Fruitfield deglacial series

Earth Science Conservation Review

Summary Full report
Ballykelly, Sistrakeel and Fruitfield deglacial series	Londonderry

Site number:	2	File Number:	C62
ESCC:	EO
Locality Type:	Inland exposure, River bank	Status:	TBC
Grid Reference:	C630224 Centroid
Google maps:	55.04544,-7.01441
County:	Londonderry	Council area:	Causeway Coast & Glens Borough Council
Period:	Quaternary
Stages:	Pleistocene

Site Description
Highlights:
The significance of the Quaternary landforms and stratigraphy around Ballykelly have been debated since Portlock's (1843) pioneer survey. In a general sense later workers such as Colhoun (1971) and Stephens et al., (1975) considered that the shelly diamicts of north Co. Londonderry were tills and associated with onshore movement of Scottish ice during the penultimate cold stage. Recent sedimentological investigations and amino acid dating of these sequences suggest that some shelly sequences are in situ (eg. Sistrakeel, Tygore/Carnakilly) and represent marine transgressions during the Early Midlandian. The overlying hummocky moraine between Limavady and Ballykelly represents a later incursion of Scottish ice during the Late Midlandian. When this ice withdrew a magnificant flat topped, Late-glacial delta formed at Fruitfield, near Limavady.
Introduction:
Three distinct Quaternary events are recorded in the stratigraphy and landforms between Ballykelly and Limavady: 1: Exposures along the flanks of small northward draining streams draining into Lough Foyle show efflux sequences of glaciomarine sediments up to 52m O.D. in front of a steep cliff. These sequences are probably of Early Midlandian age. 2: The well-developed zone of moraine between Limavady and Ballykelly is associated with deltaic and ice contact sedimentation from Scottish ice during the Late Midlandian. 3: The extensive flat delta around Limavady and Fruitfield formed after Scottish ice withdrew north eastwards at a time of High Relative Sea Level.
Description:
A section along the Ballykelly river at Sistrakeel contains five major lithofacies above stream level. Facies 1, immediately above river level, consists of stacked beds of sandy diamict separated by sandy stringers. Shell fragments and whole shells of Nuclana pernula are common. Contact with the overlying amalgamated beds of cobble gravel is transitional. The gravels of facies 2 are mainly clast-supported with strong A(p) fabrics. Facies 3 is a massive mud containing unabraided shells of Arctica islandica and a cool foraminiferal assemblage. Facies 3 grades upwards into laminated silts and stratified diamict of facies 4. The diamict comprising facies 5 is texturally similar to facies 4, but is massive, overconsolidated and shows irregular shear structures. AMS estimates on shells of Arctica islandica provided dates beyond the range of 14C dating (>45ka B.P.). Amino acid estimates suggest an Early Midlandian age. A well-defined series of ridges and hummocky ground in the lower Roe valley form a morainic complex which overlies the shelly muds and diamicts described above. The most southerly ridges occur as a broad arcuate belt of gravelly ridges at Clagan, Drumraighland and Moys. Eastwards they are replaced by hummocky till moraine which occurs at Ardmore, Glenkeen, Drumalief and Shanvey. An inner line of hummocky ridges occurs along the road between Limavady and Ballykelly forest. A temporary section suggests that the feature is composed of deltaic foresets dipping southwards. The extensive flat area from Limavady northwards to Drumbane is a large glacially-influenced delta composed of cross-bedded gravels dipping northwards. It is up to approximately 27m O.D. and is associated with high relative sea level. The meltwater channels of the Roe, Curley and Castle rivers have dissected the feature around Limavady. The northern slopes of the feature have been dissected by late and post glacial marine erosion.
Importance:
I - The three stratigraphic and morphological assemblages along the southern margins of Lough Foyle provide critical evidence for ice age events in this local area. II - The sites and landforms are important nationally for the following reasons: (i) - The Sistrakeel sequence is one of the oldest glacial sequences known in Northern Ireland. This site is stratigraphically complex and provides a window into depositional settings and ice sheet activity during the Early Midlandian. Similar sites have not been identified elsewhere which demonstrate unequivocally that major lowland ice sheets existed in northwest Britain during the Early Midlandian. (ii) - The morainic complex records a Late Midlandian ice advance from western Scotland into Lough Foyle. It demonstrates important temporal contrasts in ice sheet activity towards the north western sector of the last British ice sheet. (iii) - The morphology and stratigraphic elements of the moraine are unique in Northern Ireland. The only similar feature in GB occurs in Holderness. Both features document surging of the ice sheet margin and this has an impact on future modelling of ice sheet activity close to the continental shelf. (iv) - The Fruitfield delta is the largest extraglacial delta of late glacial age in Northern Ireland and forms part of the late glacial raised coastal features of the north coast. Generally the earliest elements of the eustatic/isostatic/tectonic system are poorly if at all preserved due to subsequent marine erosion. III - The Quaternary elements around Ballykelly have important implications for the advancement of geological concepts. These include: (i) - The glaciomarine muds at Sistrakeel demonstrate deep isosatic depression during the Early Midlandian and therefore indicate the growth of large, lowland ice sheets. To date few sites in Great Britain preserve this evidence which is critical for palaeoenvironmental and climatic reconstructions in the north eastern Atlantic fringes. (ii) - The elements within the morainic complex in the lower Roe are similar to features formed by surging ice lobes in modern settings (cf. Solheim and Pfirman, 1985). Therefore in sedimentological terms it is important to recognise the origins of specific moraines as a prerequisite to realistic ice sheet modelling and activity.
Interpretation:
The cake-like stratigraphic geometry of the facies at Sistrakeel, their lateral tabular continuity and absence of glaciotectonic deformation suggests that the sequence is in situ rather than part of an ice-rafted block. Interbedded and transitional contacts point to penecontemporaneous deposition controlled by changes in the dominant processes. The stacked beds of sandy diamict (facies 1) formed by repeated mass flows of heterogeneous debris whereas the overlying imbricated cobble gravels (facies 2) are attributed to high energy jet sedimentation. Overlying mud (facies 3) records a shut down or switch in the locus of jet activity followed by plume sedimentation with minimal ice rafting in a glaciomarine setting. Laminated muds and stratified diamict (facies 4) indicate a phase of traction current activity and mass flow as the mud was reworked. Facies 5 comprises a massive diamict with many characteristics indicative of a basal till derived from fine-grained marine muds. Erratics of basalt and chalk in this facies suggest deposition by Scottish ice which eroded the northern face of the Binevenagh scarp and moved into the Lough Foyle lowlands. Dating of marine shells in the muds suggest that this event occurred during the Early Midlandian. The presence of in situ marine muds at 52m O.D. points to substantial isostatic deflection at this time which is linked with the growth of major lowland ice sheets in the north of Ireland and western Scotland. The arcuate belt of ridges and hummocky moraine which sweeps southwards into the lower Roe basin has a gross structure similar to that formed during a major ice surge (eg. Solheim and Pfirman, 1985). Three main structural units are identified. The outer morphologically complex pattern of ridges consists of hummocky till, and ice-pushed, coarse-grained, gravelly sediments represent the maximum extent of the surge subparallel to the glacier. The inner hummocky ridges of cross-bedded sediments and large scale gravelly foresets dipping south, represent subglacial meltwater discharge into open water along the central axis of the ice lobe. At the base of the sequence a variety of shelly diamicts and subaqueous sequences (Early Midlandian age) have been overridden by the ice and show a progressive upwards increase in the degree of glacial deformation and homogenisation (eg. Mullane). The flat delta around Limavady represents meltwater discharge along the Roe valley from decaying ice masses farther south in the Dungiven depression. Its height was probably controlled by high relative sea level during the late glacial. At Fruitfield ice wedge pseudomorphs were recorded truncating the deltaic gravels. Erosion and deep incision of the once continuous delta surface has been progressive as relative sea level fell during post-glacial isostatic uplift.
Conclusions:
Three distinct Quaternary events from the Ballykelly area are well-documented in the stratigraphic and morphological record. The raised glaciomarine muds and glacial efflux sequence at Sistrakeel are associated with a basal discharge from Scottish ice during the Early Midlandian. The overlying morainic complex records a major surge event during the Late Midlandian and is related to Scottish ice. Extraglacial deltaic sedimentation into a high late glacial sea level post dates the ice sheet surge from western Scotland.
Notes:
Sistrakeel: This section occurs along the flanks of the Ballykelly river and is currently being eroded during major floods. As a result fresh exposure is maintained. The site does not need protection from this agency. However the land immediately above the site and adjacent to the minor road is currently being used as an unauthorised dump which tends to drape critical parts of the section. A "No dumping" notice exists but periodic dumping of a wide variety of household farm waste (bales) and excavated ground fill are beginning to obscure the excellent exposures. There are also several drains crossing the site transporting run-off from farm yard sources (silage effluent; manure) which is high in suspended organic and other detritus. This runs directly into the river which generally has a low discharge and cannot cope effectively with the organic waste. Generally there is an unhealthy smell around the site. Ballykelly morainic complex: This is largely intact with only one major sand pit which has now been landscaped. Aesthetically it provides rolling topography and pleasing topographic contrasts within the lower Roe valley. Land use is mainly grazing and silage production with a few fields used for crops. A disturbing feature around the old sand pit is the presence of a dirt track used by motor cycles. Fruitfield Delta: The town of Limavady is built on this feature. The extension of the delta top northwards is used for grazing and has been used as an airport during the last war. It is relatively unspoilt and forms a magnificent terrace below the Binevenagh scarp. The post- glacial, flat-bottomed meltwater channels incised into the delta are wooded and provide wetland sites and biological diversity in this area.

Keywords
Rocks:	Gravel, Sand
Fossil Groups:	Foraminifera
Fossil List:	Nuclana pernula
Relations:	Glaciomarine deposit
Geomorph:	hummocky moraine
Paleoenv:	delta

Access
Approach:	Ballykelly village lies 4km west of Limavady on the A2. Sistrakeel lies 2.5km southwest of Ballykelly.
Management:
Sistrakeel: This site can withstand geological sampling and field inspections. Care must be exercised as the route from the road to the site, traverses the dumped debris and a steep slope to stream level. Supervision and agility are required to reach this site. Notifiable operations include modification of the land surface above the site, engineering works, use of machineary, afforestation, burning of waste and dumping or discharge of any material. It is suggested that if the exposure is left alone to erode slowly, further scientific data may be revealed. The site's value would be enhanced if the dumped debris were removed and future dumping prohibited. Ballykelly: This site is almost intact though one former sand/gravel quarry is now landscaped. One face could be preserved showing foresets dipping southwards. It could also provide sites suitable for nesting birds in sandy pockets. Clearly future excavations for sand and gravel extraction should be discouraged in areas of hummocky topography which contain a number of hill-head raths. An old pit immediately on the west bank of the Roe is abandoned and is reverting back to pasture. The entire moraine is of high scientific interest and any dumping, recreational or engineering works should be notifiable. The Fruitfield delta: The site surface to the north of Limavady is relatively unspoilt with the remains of an airfield, farmhouses, a small estate and a 'club'. Clearly it is an area which is likely to be exploited for housing or commercial purposes. This should be avoided because of the uniqueness of this delta and its importance to late glacial sea level studies. Notifiable operations include modification of the existing land surface, drainage, engineering works, recreational activity, use of extraction machinery, tree planting and dumping of any materials.
Threats:	Dumping; run-off carrying silage effluent and manure; development for housing or commercial purposes.
Uses
Uses:	Farmland; sand pits; urban development.

References (3)
Colhoun, E.A., 1971. The glacial stratigraphy of the Sperrin Mountains and its relation to the glacial stratigraphy of north-west Ireland. Proceedings of the Royal Irish Academy, vol. 71B, pp.37-52.
Portlock, J.E., 1843. Report on the Geology of the County of Londonderry and of parts of Tyrone and Fermanagh. HMSO, Dublin.
Stephens, N., Creighton, J.R. & Hannon, M.A., 1975. The Late Pleistocene period in north-eastern Ireland - An Assessment. Irish Geography, vol. 8, pp.1-23.

Map(s):	See the 1:50,000 O.S. Sheet 7 (Londonderry).
Record type:	Environment Serv. GIS, ESCR report
Entered by:	Crowther, P.R.
Last updated:	28 Feb 2005

Enlander, I., Dempster, M. & Doughty, P., 2026. Ballykelly, Sistrakeel and Fruitfield deglacial series, County Londonderry, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=2. Accessed on 2026-11-05.