ESCR - Annalong Valley

Earth Science Conservation Review

Summary Full report
Annalong Valley	Down

Site number:	451
ESCC:	IS
Locality Type:	Inland exposure	Status:	TBC
Grid Reference:	J365218,J344246 Centroid, Not Entered
Google maps:	54.12761,-5.91196
County:	Down	Council area:	Newry, Mourne & Down District Council
Period:	Quaternary
Stages:	Devensian

Site Description
Highlights:
The pattern of moraines in the Annalong River valley records two distinct advance phases during the Midlandian period. The terminal moraine of the earlier, larger advance records ice reaching to within 1.7km of the present coastline at Mullartown (J365218). Ice spread out as a lobe from the topographic constraints at the exit from the mountains, and associated moraines formed during the lobes decay cut across moraines of the earlier Midlandian retreat phase on the lower ground. Along the lower valley floor, the complex is bounded by moraine benches and mounds banked against the eastern flank of Slieve Binnian and the western flank of Long Seefin. A pronounced cross-valley ridge (J344246) cuts across subdued cross-valley recessional moraine ridges and records a later readvance of ice from the Castles of Commedagh corrie, the headwall of which is ca. 450m long and up to 35m high. Hummocky moraines and flutes associated with ice retreat through the upper valley record at least nine ice front positions along 2km of the valley floor associated with this readvance. The Cove Lough (430m a.s.l.), Binnian Lough (460m a.s.l.) and Slievelamagan (ca. 450m a.s.l.) corries are perched along the valley sides. The Blue Lough occupies a well-developed bowl at the southern foot of Slievelamagan, at the same elevation as the adjacent valley floor (330m a.s.l.).
Description:
The south/southeast trending Annalong valley occurs from 500m a.s.l. in the southern rim of the Mourne Mountains, Co. Down. The valley section north of Dunnywater is encircled by a ring of mountain peaks. Slieve Commedagh lies to the north, Cove Mountain, Slievelamagan and Slieve Binnian lie to the west, and Rocky Mountain and Long Seefin to the east. The upper Annalong River valley is underlain by G2 granite, which forms the core of the eastern Mournes (Wilson, 1972). This quartzose granite, with abundant dark quartz, and local porphyritic orthoclase, is the most abundant Tertiary bedrock in the eastern Mournes. The boundary between granite and Silurian greywacke is ca. 500m south of Dunnywater Bridge, subparallel to the coast. The Annalong valley complex covers the valley floor and extends up the valley sides. South of Dunnywater the shape of the complex is lobate, and has a maximum width of ca. 2.1km, narrowing from 1km at Dunnywater to ca. 200m at the threshold of the Castles of Commedagh corrie. Deposits will be described from south to north, from the coastal lowlands into the upper Annalong River valley. ANNALONG RIVER VALLEY RIDGES The southern limit of the complex at Mullartown is formed by a 2.5km long indistinct broad (<500m), low (<3m high), rounded east/west tending ridge which has a variably steep to gentle southward facing slope. It truncates four low relief (<5m high) northwest to southeast trending ridges. At least six low relief (<3m high) arcuate ridges and benches occur for 1.3km northwards between the ridge and the Head Road (J347220). The benches appear to be degraded ridges and frequently show a lateral transition to low rounded ridges. West of the Annalong River three meltwater channels (<80m wide) are cut through the ridges, with little topography occurring to the east of the river. Ridges become more strongly arcuate upslope towards the bedrock high of Carrick Big. Frequent small exposures in the riverbank contain beds of stratified sand and gravel. A 500m long, 200m wide and 10m high ridge occurs immediately south of Carrick Big (J353222). An overgrown exposure in the ridge flank contains interbedded sand, gravel and diamict characterised by rapid lateral transitions. Two smaller, cross-valley arcuate ridges occur to the east and west of the southern end of the ridge. At the entrance to the enclosed Annalong valley, a well-defined, cross-valley ridge occurring on the lower slopes of Slieve Binnian cross-cuts a ridge which trends sub-parallel to the ridges occurring along the length of the coastal lowland tract (J342217). From Carrick Big northwards, a regular pattern of continuous, well-defined though subdued rounded cross-valley ridges (<200m wide by <3m high), benches and subdued, aligned hummocks occur into the upper Annalong River valley. The valley head is a shallow bowl 350m across bounded to the south by a low round-crested ridge 100m wide, and to the west and east by well-marked rounded benches. The entrance to the upper 2.5km of the valley at Mullartown Upper is dominated by an arcuate ridge up to 400m wide (J344246). The southern slope of the ridge is 5m high, and the hummocky crest has many clustered and isolated boulders. Degraded exposures in the ridge contain poorly stratified coarse sand and numerous isolated boulders. A well-marked trimline below Cove Lough (J339262) trends north to south at ca. 400m a.s.l., sloping southwards towards the upper surface of the ridge. Occasional exposures (<1m long and <0.6m high) along the riverbank north of the ridge contain interbedded horizontal and cross-laminated rippled sand, granules and occasionally silt (J343256) separated by erosional boundaries. Discontinuous hummocks (<3m high) occur in at least nine cross-valley belts between the ridge and the entrance sill of The Castles corrie. Two round-topped, slightly arcuate ridges (<200m long) trend north to south on the valley floor. Belts of hummocks are confined to within Cove Lough and Binnian Lough corries. Deposits associated with the Slievelamagan corrie are mainly arcuate benches and hummocks against the side of the mountain, but the most distant ridge occurs on the valley floor (J337255), where it cuts across a ridge cross-valley ridge. Ridges also occur at the entrance of the Blue Lough corrie, where they cross-cut cross-valley ridges between Slievelamagan and Slieve Binnian.
Importance:
The Annalong valley complex contains landforms and landform patterns which demonstrate the non-trivial nature of ice-mass and climatic oscillations during a deglacial period. The landforms indicate that the valley was influenced by at least two principal glacial events, of different magnitudes. The earlier, larger glaciation of the valley filled the valley and reached the valley mouth, probably occurred during the main Late Devensian glaciation of the Northern Hemisphere (ca. 22ka B.P.). The valley glacier appears to have cross-cut the retreat moraines formed by decaying ice which occupied the coastal lowlands to the south and east, which probably had its origins to the north and west in the Lough Neagh basin. The ice must have continued to expand during the regional deglaciation. This conforms to the idea that the deglaciation of the Irish Sea basin glacier and coastal fringe of eastern Ireland was led by dynamic properties of the ice sheet i.e. marine downdraw, not climatic forcing. The smaller readvance occurred during the period of climatic deterioration at the end of the Devensian period known as the Loch Lomand stadial or Little Ice Age.
Interpretation:
The northwest to southeast trending moraines on the lowlands at Mullartown record the withdrawal towards the northeast of ice around the eastern flank of the Mournes. The outer limit marked by moraine ridges relating to ice from the Annalong River valley crosscut these and therefore post-dates the retreat of lowland ice. The ridge marks the curved terminus of an ice lobe front across the coastal slope. This crosscutting relationship indicates that ice activity in the Annalong River valley is associated with a readvance of ice south from the valley. Between the lobe terminus and the Head Road (J347220) at least six low relief (<3m high) arcuate ridges and benches in 1.3km record retreat of the ice front towards the mountains. Benches are degraded moraine ridges and frequently show a lateral transition to low rounded ridges. Recessional moraines on the coastal slope record retreat of an active icefront northward into the valley. Carrick Big is a bedrock high which divided ice flow at the entrance of the valley. The medial moraine and associated arcuate moraines immediately to the south of Carrick Big record the separation and recession of the ice margin around the high ground. Subdued moraines to the north of Carrick Big record the retreat of active ice into the valley head between Slieve Binnian and Slievelamagan and into the Castles of Commedagh corrie. The broad moraine ridge at the entrance to the upper Annalong River valley (J344246) cuts across moraines associated with this readvance of mountain ice. The ridge marks the furthest extent of a glacier tongue which cut across at least four moraine ridges of the earlier advance. The ridge records a second readvance of mountain ice and a long-lived re-equilibration of the ice front. Vaguely stratified sediments in the ridge are probably outwash from a slowly retreating ice front. The hummocky surface records melting of buried ice masses, while boulders record debris rolling off the ice front. The contrast between subdued landforms south of the moraine ridge and well-marked hummocks to the north also implies a hiatus between depositional episodes. The trimline below Cove Lough records a boundary between frost-shattered and glacially eroded terrain (e.g. Ballantyne & McCarroll, 1995). Two round-topped, slightly arcuate ridges (<200m long) which trend north to south on the valley floor are interpreted as fluted moraines. Poorly exposed sediments behind the moraine ridge probably record inter-moraine meltwater ponding. Cross-bedding is the result of low velocity flow, with grain flow down distal slopes (Church & Gilbert, 1975). Erosional contacts record the onset of more dynamic flows. Interbedding of variable sediment sequences is typical of prograding outwash environments (Rust & Romanelli, 1975). Rippled contacts are evidence of bottom currents. The widening of the valley floor south of J340254 is inferred to be the result of the increased erosive capacity of an ice mass formed from the amalgamation of ice in the valley with ice in the trough between Slieve Binnian and Slievelamagan. Moraines south of Carrick Big record a locally generated readvance of mountain ice following the main retreat phase of the Late Midlandian ice sheet. The valley north of Hares Castle (J345255) has a well-defined U-shaped cross-section, with superimposed hummocky moraines associated with ice from the corrie glacier. Near vertical slopes below the mouth of the Cove Lough and Binnian Lough corries are not conducive to moraine preservation. Moraines have been preserved on the gentler slopes below the Slievelamagan and Blue Lough corries. Moraines formed by glaciers emerging from these corries cut across moraines related to the main valley glacier. The Castles of Commedagh corrie was the major source of the valley ice, which was augmented by ice from smaller corries at Cove Lough (J337263), Slievelamagan (J333260), Blue Lough (J327252) and Binnian Lough (J325242), and from the valley head to the east of the Slieve Binnian/Slievelamagan col. Readvance glaciers in neighbouring valleys terminated at a similar altitude (70-90m a.s.l.) to Annalong River valley ice. Valley ice readvance conforms to the regional pattern of Late Midlandian readvance which includes readvance of the Carlingford Lough ice lobe. Moraines at the entrances of the Slievelamagan and Blue Lough corries cut across moraines which record retreat of valley ice into the Annalong River valley. Cross-cutting moraines, trimlines and hummocky moraines have been used as criteria for establishing the limits of glaciers of Loch Lomond Readvance age (Sissons, 1980; Thorp, 1981) which in Ireland is roughly analogous to the Nahanagan phase (Colhoun et al. 1980). A late resurgence of corrie ice is also found in adjacent valleys (see Attical Complex Overview Key Site 447) and may be synchronous with corrie ice expansion in the Annalong River valley.
Notes:
For overview and site specific information on other sand and gravel sites within the Mourne Mountains area see the following sites: Key Site 440 - Mourne Plain Complex - Overview Key Site 447 - Attical Complex, Mourne Mountains - Overview Key Site 448 - Bloody Bridge River Valley Complex, Mourne Mountains - Overview Key Site 449 - Northeast Mournes Complex - Overview Key Site 450 - Western Mournes - Overview For general information and references on the sand and gravel landscapes of N. Ireland, and directions to sites other than those within the Mourne Mountains area, see the following site: Key Site 439 - Introduction to the Sand and Gravel Landscapes of N. Ireland

Keywords
Geomorph:	corrie glacier, cross-valley moraine, readvance moraine

Access
Management:
The southern, lobate part of the complex is entirely within the predominantly agricultural area of the Mourne Mountains footslopes. The higher fields are mainly given over to rough grazing, and here moraines are better preserved than those downslope. Ongoing reclamation involves the excavation and removal or redistribution of subsurface boulders, resulting in the effective smoothing of field surfaces. However, the removal of low relief features does little to detract from the already poor landscape quality. Valley moraines are an integral part of the upland landform association, and have not been exploited for their limited sand and gravel resources. It is likely that this will continue to be the case, due to their remoteness, poor quality and small size. The Annalong River valley is not a major route into the Mournes, although with increasing leisure use of mountain areas generally, possible future degradation of relatively fragile moraines should be monitored.

Access

Management:

The southern, lobate part of the complex is entirely within the predominantly agricultural area of the Mourne Mountains footslopes. The higher fields are mainly given over to rough grazing, and here moraines are better preserved than those downslope. Ongoing reclamation involves the excavation and removal or redistribution of subsurface boulders, resulting in the effective smoothing of field surfaces. However, the removal of low relief features does little to detract from the already poor landscape quality. Valley moraines are an integral part of the upland landform association, and have not been exploited for their limited sand and gravel resources. It is likely that this will continue to be the case, due to their remoteness, poor quality and small size. The Annalong River valley is not a major route into the Mournes, although with increasing leisure use of mountain areas generally, possible future degradation of relatively fragile moraines should be monitored.

References (7)
Ballantyne, C.K. & McCarroll, D., 1995. The vertical dimensions of Late Devensian glaciation on the mountains of Harris and southeast Lewis, Outer Hebrides, Scotland Journal of Quaternary Science, vol. 10 numb. 3, pp.211-223.
Church, M. & Gilbert, R., 1975. Proglacial fluvial and lacustrine sedimentation Society of Economic Palaeontologists & Mineralogists Special Publication, numb. 23 In Glaciofluvial and glaciolacustrine sedimentation, pp.22-100, Tulsa, Oklahoma.
Colhoun, E.A. & Synge, F.M., 1980. The cirque moraines at Lough Nahanagan, County Wicklow, Ireland Proceedings of the Royal Irish Academy, vol. 80 pt. B, pp.25-45.
Rust, B.R. & Romanelli, R., 1975. Late Quaternary subaqueous outwash deposits near Ottawa, Canada Society of Economic Palaeontologists & Mineralogists Special Publication, numb. 23 In Glaciofluvial and glaciolacustrine sedimentation, pp.177-192, Tulsa, OK.
Sissons, J.B., 1980. The Loch Lomond Advance in the Lake District, northern England Transactions of the Royal Society of Edinburgh: Earth Sciences, vol. 71, pp.13-27.
Thorp, P.W., 1981. A trimline method for defining the upper limit of Loch Lomond Advance glaciers: examples from the Loch Leven and Glen Coe areas Scottish Journal of Geology, vol. 17, pp.49-64.
Wilson, H.E., 1972. Regional Geology of Northern Ireland. HMSO, Belfast.

Record type:	ESCR report
Entered by:	E M Porter

Enlander, I., Dempster, M. & Doughty, P., 2026. Annalong Valley, County Down, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=451. Accessed on 2026-11-03.