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Earth Science Conservation Review
| Mourne Plain Complex - Cranfield Moraine | Down |
| Site number: | 441 | ||
| ESCC: | IS | ||
| Locality Type: | Inland exposure | Status: | TBC |
| Grid Reference: | J32633168 End(s) of linear site | ||
| Google maps: | 54.21662,-5.96726 | ||
| County: | Down | Council area: | Newry, Mourne & Down District Council |
| Period: | Quaternary | ||
| Stages: | Late Midlandian | ||
| Site Description | |
|---|---|
| Description: | |
This ridge moraine occurs to the north of Cranfield Point as a shallow, eastward curving arc, convex to the east, rising in altitude to the east towards the footslopes of Knockchree Mountain (326300 316800). At this point it turns westward along the lower slopes of Rocky Mountain (1.2km to the west) and Formal (323500 316800). The moraine is a major landscape feature, forming a wide, smooth and occasionally double crested ridge. The ridge is 150-300m wide along its lowland section, becoming narrower (~100m), along the lower slopes of the mountains. The crest rises from 20m a.s.l. at Cranfield to 100m a.s.l. at Tullyframe (326300 316800) over a distance of 7.5km. At the latter location the ridge crest is 70m above the local topography to the west. From the crest line it descends in a series of step-like levels westwards, over a distance of 1km, to the fringes of Carlingford Lough. The eastern margin of the moraine is bounded by the White Water River for 1km south of Tullyframe, where it breaches the ridge to flow southward and then westward into Carlingford Lough. Quarry exposures in this northern section of the ridge near Glenloughan (325400 316400) and Tullyframe show facies sequences which illustrate the sedimentological processes involved in the accumulation of the Cranfield moraine. INTERPRETATION Glenloughan facies interpretation The stacked beds of crudely stratified diamict are typical of repeated debris flows (Middleton & Hampton, 1976). Sandy stringers, clast lines and isolated gravelly pods within the diamict record variable winnowing processes. This sedimentation pattern is typical of a range of cohesionless flows occurring on subaqueous slopes (Postma, 1986). Interbedded sand and silt (F2) record temporal and spatial variations in grain flow regime and deposition rates from suspension (Rust & Romanelli, 1975) associated with subaqueous sedimentation (Shaw, 1975). Rhythmic bedding reflects cycles of waning flow conditions, with a gradual decline in turbulence associated with increases in deposition from suspension. This is a product of variability in sediment supply or changing locations of glacial effluxes. Fining up and coarsening up sequences in F3 record small-scale variations in flow parameters. Bed continuity is the result of deposition of clast-rich sediment gravity flows in a subaqueous setting. Cobble lines at bed boundaries are the result of winnowing by flowing water (Collinson & Thompson, 1982). Sand beds record flow during periods of diminished flow, while welded contacts suggest rapid alternation between differing flow regimes (Rust & Koster, 1984). Together with bed continuity and lateral uniformity of bed thickness, these features suggest subaqueous deposition . High angle faults disrupting the sand and gravel with little vertical displacement of beds are extensional. They are probably a result of local volume changes due to the removal of ice support. Vertical clasts record infill by gravity processes from adjacent beds. Folded beds, which show no evidence of shearing and are closely associated with vertical faults, are evidence for slumping of saturated sediments. Subsequent deposition of flat-lying gravel beds also suggest that deformation was syndepositional. The exposure is interpreted to represent deposition in an ice-contact marginal waterbody. The efflux was characterised by shifts in sediment type and flow velocity. Variability in sediments is the result of changing sediment input and flow strengthening. The facies sequence shows a general increase in the degree of sorting over depositional time and is associated with increased fluvioglacial transport. The Cranfield ridge is therefore inferred to result from the amalgamation of subaqueous spreads at an ice margin which was situated towards the west and southwest. | |
| Interpretation: | |
Glenloughan facies interpretation The stacked beds of crudely stratified diamict are typical of repeated debris flows (Middleton & Hampton, 1976). Sandy stringers, clast lines and isolated gravelly pods within the diamict record variable winnowing processes. This sedimentation pattern is typical of a range of cohesionless flows occurring on subaqueous slopes (Postma, 1986). Interbedded sand and silt (F2) record temporal and spatial variations in grain flow regime and deposition rates from suspension (Rust & Romanelli, 1975) associated with subaqueous sedimentation (Shaw, 1975). Rhythmic bedding reflects cycles of waning flow conditions, with a gradual decline in turbulence associated with increases in deposition from suspension. This is a product of variability in sediment supply or changing locations of glacial effluxes. Fining up and coarsening up sequences in F3 record small-scale variations in flow parameters. Bed continuity is the result of deposition of clast-rich sediment gravity flows in a subaqueous setting. Cobble lines at bed boundaries are the result of winnowing by flowing water (Collinson & Thompson, 1982). Sand beds record flow during periods of diminished flow, while welded contacts suggest rapid alternation between differing flow regimes (Rust & Koster, 1984). Together with bed continuity and lateral uniformity of bed thickness, these features suggest subaqueous deposition . High angle faults disrupting the sand and gravel with little vertical displacement of beds are extensional. They are probably a result of local volume changes due to the removal of ice support. Vertical clasts record infill by gravity processes from adjacent beds. Folded beds, which show no evidence of shearing and are closely associated with vertical faults, are evidence for slumping of saturated sediments. Subsequent deposition of flat-lying gravel beds also suggest that deformation was syndepositional. The exposure is interpreted to represent deposition in an ice-contact marginal waterbody. The efflux was characterised by shifts in sediment type and flow velocity. Variability in sediments is the result of changing sediment input and flow strengthening. The facies sequence shows a general increase in the degree of sorting over depositional time and is associated with increased fluvioglacial transport. The Cranfield ridge is therefore inferred to result from the amalgamation of subaqueous spreads at an ice margin which was situated towards the west and southwest. | |
| Notes: | |
For site specific information on other sand and gravel sites within the Mourne Plain Complex see the following sites: Key Site 442 - Glenloughan Pit Key Site 443 - Tullyframe Pit Key Site 444 - Moore Lodge Moraine Key Site 445 - Sandpiper Pit Key Site 446 - Kilkeel Cliff For overview information and references on the Mourne Plain Complex see the following site: Key Site 440 - Mourne Plain Complex - Overview For overview and site specific information on other sand and gravel sites within the Mourne Mountains area see the following sites: 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 Key Site 451 - Annalong Valley For general information and references on the sand and gravel landscapes of N. Ireland, and for directions to sand and gravel 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 | |
|---|---|
| Relations: | Glacial deposit, Glaciomarine deposit, Glaciotectonic |
| Geomorph: | ice lobe, moraine ridge, outwash |
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Mourne Plain Complex - Cranfield Moraine, County Down, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=441. Accessed on 2026-11-06. |
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