ESCR - Northeast Mournes Complex

Earth Science Conservation Review

Summary Full report
Northeast Mournes Complex - Overview	Down

Site number:	449
ESCC:	IS
Locality Type:	Inland exposure
Grid Reference:	J345170,J370305,J330215,J383236 Centroid, Corners of site, Not Entered
Google maps:	54.08505,-5.94466
County:	Down	Council area:	Newry, Mourne & Down District Council
Period:	Quaternary
Stages:	Late Midlandian

Site Description
Highlights:
Well-preserved ridges in the southern section of the Northeast Mournes unit record the retreat of an ice-sheet during the Late Midlandian period from the coastal lowlands to the north and east of the Mourne Mountains. The morainic belts were deposited following the lowering of the ice sheet profile below the high ground of the Mournes and its separation into two lobes linked to their centres of provenance in Lough Neagh. The ice marginal position and retreat direction was subject to topographic control during this retreat stage, resulting in the surrounding of the massif by the ice-sheet. Separation of the northern and southern arms of the ice took place in the vicinity of Balleyveagh Beg (J332212) and Ballymartin (J345170). The large, meltwater dissected ridge which is the result of glacier input from both north and south reaches the modern coast at Ballymartin Hill. Dissected ridges immediately to the north of this ridge contain numerous enclosed depressions. As the lowland narrows to the north, moraines are restricted to their lateral elements, following removal of their frontal sections by coastal erosion. Moraines pinch out where the eastern flank of Millstone Mountain reaches sea level (J385285). Ice continued its retreat along the northern flank of the Mournes, where benches trend upslope towards the west along the lower mountain slopes. As ice lowered further, retreat patterns were controlled by a chain of bedrock highs which form an arc between McLeans' Hill (J340340) and Stang Tops (J255305), resulting in nested moraine ridges in the gaps between the hills. Cross-cutting moraine ridges in the Trassey River valley (J300300) and at McLeans' Hill record the furthest extent of ice which readvanced following the main phase of Late Midlandian retreat. High late-glacial sea levels are recorded by marine notches and associated benches which cut across moraine ridges between Glasdrumman (J380235) and Ballymartin. A spread of beach sand and gravel extends south from Dunmore Hill (J243386) and pinches out north of Ballymartin Hill. A raised postglacial cliffline has been cut into late glacial beach deposits at Glasdrumman. Postglacial marine erosion has truncated moraine ridges at Newcastle (J373320), with spreads of beach sediments at Donard Park (J373306).
Description:
Most of the southern section is underlain by Silurian greywacke. The lower mountain slopes are underlain by Tertiary G2 quartzose granite intruded into the Silurian country rock (Wilson, 1972). Bedrock is rarely revealed at lower altitudes, due to the cover of glacigenic deposits. Ballymartin Hill contains a minimum depth of 60m of these sediments. Moraine ridges to the north of Ballymartin are generally less massive, drift depths are thinner, and bedrock outcrops are occasional. Deposits also thin towards the lower slopes of the mountains, and bedrock exposures are more frequent. The northern section is entirely underlain by Silurian greywacke, which frequently crops out in valley bottoms and on mountain and hill slopes. Moraines are described from southwest to northeast in the southern section, and from east to west in the northern section, the general direction of ice retreat. Late glacial raised beaches are described, followed by postglacial raised beaches. Exposures of raised beach deposits (J383236) and moraine ridge deposits (J378237) will be described to illustrate the processes involved in landform construction. For site specific information on the Northeast Mournes Complex see the following sites: Key Site 459 - Northeast Mournes Moraines Key Site 460 - Northeast Mournes Raised Beaches
Importance:
Moraines record retreat of the main Late Midlandian ice sheet, with numerous well-preserved moraine ridges reflecting frequent stillstands. Moraines in the northern section record a readvance of ice in the area, synchronous with ice which entered Carlingford Lough around 15ka B.P. Ice proximal glaciomarine mud underlying emergent beach facies contain a dateable fossil fauna which helps to place deglacial events within a rigorous temporal framework. Beach notches are evidence of late- and postglacial changes in relative sea level, and record the relationship between high late glacial sea levels and the retreating ice front.
Interpretation:
Moraines on low-lying land to the northeast of the Mournes record retreat of Late Midlandian ice towards its source region in the Lough Neagh Basin. Moraines which mark a readvance of ice through gaps in bedrock highs to the north of the Mournes front the drumlin swarms of northern County Down. Moraine banks at Killard Point and Dundrum have a similar relationship to the drumlins (McCabe et al., 1984), and may be continuous with the North Mournes moraines.
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 450 - Western Mournes Complex - Overview Key Site 451 - Annalong Valley 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:	raised beach, recessional moraine

Access
Management:
Gravel deposits have been little exploited in the northeastern Mournes. Deposits in moraine ridges are probably of little economic importance because of their coarseness. However, raised beach deposits are better graded and sandier, are easier to access, and may be more vulnerable to exploitation. The narrowness of the raised beaches means that any exploitation would inevitably be visually intrusive.

Access

Management:

Gravel deposits have been little exploited in the northeastern Mournes. Deposits in moraine ridges are probably of little economic importance because of their coarseness. However, raised beach deposits are better graded and sandier, are easier to access, and may be more vulnerable to exploitation. The narrowness of the raised beaches means that any exploitation would inevitably be visually intrusive.

References (6)
Bourgeois, J. & Leithold, E.L., 1984. Wave-worked conglomerates - Depositional processes and criteria for recognition In CSPG Memoir 10, Sedimentology of Gravels and Conglomerates, pp.331-343.
Clifton, H.E., 1973. Pebble segregation and bed lenticularity in wave-worked versus alluvial gravel Sedimentary Geology, vol. 20, pp.173-187.
Lawson, D.E., 1982. Mobilization, movement and deposition of active subaerial sediment flows, Matanuska Glacier, Alaska Journal of Geology, vol. 90, pp.279-300.
McCabe, A.M., Dardis, G.F. & Hanvey, P.M., 1984. Sedimentology of a Late-Pleistocene submarine moraine complex, County Down, Northern Ireland. Journal of Sedimentary Petrology, vol. 54, pp.716-730.
Middleton, G.V. & Hampton, M.A., 1976. Subaqueous sedimentation transport and deposition by sediment gravity flows In Marine sediment transport and environmental management, pp.197-218 Wiley, New York.
Postma, G., 1986. Classification for sediment gravity-flow deposits based on flow conditions during sedimentation Geology, vol. 14, pp.291-294.

Record type:	ESCR report
Entered by:	E M Porter

Enlander, I., Dempster, M. & Doughty, P., 2026. Northeast Mournes Complex - Overview, County Down, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=449. Accessed on 2026-11-08.