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Earth Science Conservation Review
| Fruitfield Delta, Limavady | Londonderry |
| Site number: | 468 | ||
| ESCC: | IS | ||
| Locality Type: | Inland exposure, Pit | Status: | TBC |
| Grid Reference: | C647220,C677228,C678284 Corners of site, Not Entered | ||
| Google maps: | 55.04163,-6.98791 | ||
| County: | Londonderry | Council area: | Causeway Coast & Glens Borough Council |
| Period: | Quaternary | ||
| Site Description | |
|---|---|
| Highlights: | |
The Fruitfield delta occurs at around 18m a.s.l., is flat-topped, and formed by extraglacial outwash supplied largely along the Roe channel, which prograded into a late-glacial sea. It post-dates the Ballykelly moraine. Measurements on the delta top suggest a relative sea level up to about 18m O.D. The delta is the largest onshore raised feature on the north coast of N. Ireland from the late-glacial period. Its flat surface is generally well-preserved, extensive and visible (especially at Dowland) except around the urban area of Limavady. It is one of the highest late-glacial marine deltas known in Northern Ireland and forms a distinctive, largely unspoilt, terrace-like feature bordering the Lough Foyle lowlands. At Dowland the extensive fragment forms a striking topographic contrast with the steep, rock-dominated slopes of the Tertiary mass of Ballymaglin (269100 429200) and Binevenagh Mountain (269700 429400) to the east. The delta top and associated poorly-drained flat-bottomed meltwater channels provide significant aesthetic additions to the appearance of the lower Roe valley and margins of the Lough Foyle estuary. | |
| Description: | |
The Fruitfield delta is a wedge-shaped body, extending from Tamlaght (264700 422000) northeastwards to Limavady, as far south as the Roe valley hospital (267700 422800) and northeastwards to Shanvey (267800 428400). Meltwater incisions, now occupied by the courses of the present day Roe, Castle and Curly rivers have dissected the delta into four separate terrace-like topographic flats, named here as Dowland (267600 426400), Drenagh (268800 4237700), Limavady and Lisnakilly (265700 423300). The broad, alluvial filled channels are bordered by glaciofluvially-eroded, steep slopes. To the north of the delta, a flat coastal plain forms the shoreline with Lough Foyle, while to the east the extensive topographic flat at Dowlands abuts on, and provides a striking topographic contrast with the steep rock slopes of Binevenagh mountain. To the west the area of the Lisnakilly flat-top is truncated to the north by a raised beach notch (at 10m O.D.) and feathers onto the Ballykelly moraine to the south. The flat surfaces of the Dowland, Drenagh, and Limavady fragments occur at around 18m a.s.l., with the Lisnakilly fragment occurring at around 16m a.s.l. Surfaces are flat, gently sloping seawards, with no kettle holes. The northern, approximately 6km long, margin is cut by both late and post-glacial sea level beach notches. Fruitfield Exposure One small, partially overgrown pit at Fruitfield (268300 424300) contains a 3-4m long by 2m high exposure of interbedded trough cross-bedded sands, pebbly sands and silty drapes. The sequence generally fines upwards. The exposure consists of five, interbedded, 'units' of shallow scour infill composed of cross-bedded sands and pebbly gravels. Unit 1 consists of poorly-sorted cross-bedded pebbly sands, dipping at <5§ to 160§N. Units 2, 3 and 5 consist of normally graded, small-scale, planar cross-bedded sands (dipping towards 010§N) and low angle (<5§) lamination/bedding. Unit 4 consists of well-sorted, massive sand with discontinuous horizontally laminated silt/mud drapes. Clasts are mainly derived from schistose and granitoid rocks. In 1989 a 2m deep ice wedge pseudomorph was recorded at the top of this gravel exposure. | |
| Importance: | |
The Fruitfield delta is important at a national level, as it documents a phase of high relative sea level during the late-glacial. It is the only large-scale, clearly documented extraglacial delta on the north coast of Northern Ireland. Features diagnostic of high relative sea level provide evidence of past sea level changes, coastal change and rapid environmental change during the late-glacial period. | |
| Interpretation: | |
The delta surface is probably associated with a relative sea level around 18m a.s.l. Based on the geologic evidence of granitoid erratics from Co. Tyrone and the location of the delta at the mouth of the Roe meltwater channel, the sediment supply route is inferred to have been mainly along the Roe channel, associated with ice decay in the upper Dungiven basin as ice margins receded across the northern cols in the Sperrin range. The topographic position of the delta shows that it cuts across the eastern margin of the Ballykelly moraine, in the lower Roe valley around Limavady. It is inferred therefore that the delta was deposited after Scottish ice associated with the deposition of the Ballykelly moraine vacated this coastal segment. The low angle cross-bedded sands and gravels exposed at Fruitfield, located between 8 and 10m a.s.l., suggest that at least the lower part of the delta consists of glacial outwash that prograded seawards. Available evidence suggests that the outwash, in the form of a low angle, gravelly fan prograded into the sea, though it is difficult to separate subaqueous from subaerial components. However, the presence of numerous mud drapes and massive sand beds within the sequence suggests that most is subaqueous. The absence of a morainic ridge at the head of the delta input (in the direction of meltwater flow), and its gently rising surface, suggest the delta is an example of an extraglacial delta. The delta surface is probably part of the late-glacial raised beach system along the north coast of Ireland and developed in response to a substantial meltwater and debris output northwards along the Roe valley. There is no evidence to suggest that an ice dam was responsible for the development of the flat delta surface. Notching of the feature by late-glacial beaches around 10m O.D. at Oakdene (264000 422600) suggests a fall in relative sea level after delta formation. However precise dating of glacial moraine formation events is difficult due to the lack of preserved shelly or organic horizons. It is tentatively suggested that the delta aggraded around 16-15ka B.P., based on current notions of regional deglacial events along the north coast. Ice wedge casts indicate that severe periglacial conditions persisted after delta formation after a fall in relative sea level. | |
| Notes: | |
For general information and references on the sand and gravel landscapes of N. Ireland, and for directions to other regional sand and gravel sites, see the following site: Key Site 439 - Introduction to the Sand and Gravel Landscapes of N. Ireland | |
| Keywords | |
|---|---|
| Rocks: | Sand |
| Relations: | Glacio-fluvial sediment, Late-glacial deposit |
| Geomorph: | deltas |
| Paleoenv: | delta |
| Measurements | |||||
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| Length: | Width: | Height: | |||
| Depth: | Area: | 7km2 | |||
| Access | |
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| Management: | |
The Fruitfield delta forms a flat-topped sediment body at the exit of a picturesque bedrock depression at the mouth of the Roe river on the southern shore of Lough Foyle. Part of the estuary shoreline, protected for its wildlife habitats as a Nature Reserve, and the scenic skyline of Inishowen's (Co. Donegal, R. of Ireland) mountain range are both visible from most locations on and near the delta. The dissected delta and its flat-top occupy an area of approximately 7km2 with 80% of this in pristine, undeveloped condition. The frontal (northern) slopes of the delta fragments are stepped seawards toward the present day shoreline of Lough Foyle as a result of the action of both meltwater and marine erosion. Steep, erosional slopes, cut by meltwater and the current Roe river are prominent features on the Londonderry/Limavady road at the western edge of the town. The steep sides (10-20§) and flat poorly-drained bottoms of the Castle and Curley meltwater channels (forming the Drenagh, Limavady and Dowlands delta fragments) are visible from the A2 road near Castle Bridge (268200 424000). The meltwater channel sides are predominately grassed, some also having scrub or more rarely tree-stands. At Fruitfield (in the Drenagh fragment), near Castle Bridge, a small scale pit, now almost entirely grassed, forms the only significant exposure of the deltaic sediments. Small scale dissection of the frontal (northern) margins has also occurred through post-depositional drainage of the delta-top (e.g. south-east of Shanvey) and the formation of raised beach notches. A vista of Lough Foyle from the surface of the delta, and additions to the aesthetics of the local countryside made by the distinctive topography of the dissected delta are lost largely as a result of remnant deciduous woodlands and extensive hedgerow field boundaries. Rural construction consists of isolated farm buildings except for the modern housing estate and industrial park at Grannagh which both occupy skyline locations. The industrial buildings, while not being particularly elevated, are highly visible from many local viewpoints in the lower Roe valley and from the Dowlands delta fragment. The urban area of Limavady has utilised the topographic high provided by the delta and completely occupies one of the delta fragments. The majority of the delta's rural flat top has been cleared of the woodland that must have covered it prior to improvement for farming purposes. Agriculture is divided between livestock (cattle and sheep) grazing and arable crop production. No examples of bog formation or sites of archaeologically important features have been observed or mapped on the delta-top. The almost perfectly horizontal, extensive delta-top is in excellent, pristine condition, with particular note placed on the 3.5km2 area at Dowlands. Quarrying of the sediments has remained at a minimum although a significant mineral aggregate resource exists at this location. | |
| Uses | |
| Uses: | The urban area of Limavady completely occupies one of the delta fragments. The majority of the delta's rural flat top has been cleared for farming purposes. Agriculture is divided between livestock (cattle and sheep) grazing and arable crop production. |
| References (1) | |||
|---|---|---|---|
| McCabe, A.M., Carter, R.W.G. & Haynes, J., 1994. A shallow marine emergent sequence from the northwestern sector of the last British ice sheet, Portballintrae, Northern Ireland. Marine Geology, vol. 117, pp.19-34. | |||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Last updated: | 6 Jun 2005 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Fruitfield Delta, Limavady, County Londonderry, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=468. Accessed on 2026-11-06. |
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