ESCR - Six Mile Water

Earth Science Conservation Review

Summary Full report
Six Mile Water	Tyrone

Site number:	488
ESCC:	IS
Locality Type:	Inland exposure	Status:	TBC
Grid Reference:	J176848,J262896 End(s) of linear site, Not Entered
Google maps:	54.69795,-6.17594
County:	Tyrone	Council area:	Antrim & Newtownabbey Borough Council
Period:	Quaternary

Site Description
Highlights:
The glaciofluvial topography along the Six Mile Water depression probably represents part of a subglacial palaeohydraulic system which conducted meltwater generally northwestwards from the Lough Neagh lowlands during the last deglacial event. The palaeoflow is associated with a high piezometric surface which forced meltwater flow uphill against the local topographic gradient.
Description:
A sinuous, discontinuous, up to 1km wide belt of 3-4m high glaciofluvial hummocks, ridge segments and mounds occurs for approximately 18km along the tectonic bedrock depression of the Six Mile Water valley in Co. Antrim. The shallow, 7-8km wide valley is defined to the north and south by the rising bedrock slopes of the surrounding Antrim plateau (up to 300m O.D.) and contains southwest/northeast streamlined bedrock ridges at its margins. The deposits occur from approximately 40m O.D. southeast of Antrim (317600 384800) to a maximum of 75m O.D. at Doagh (326200 389600), 14.5km to the northeast. The belt is located predominately on the northern side of the Six Mile Water river, trending generally southwest/northeast along the valley axis. The sinuous line of the belt consists of four clusters of hummocks and ridge segments (A to D). The deposits are described from southwest to northeast: (A) Immediately southeast of Antrim, a small (<0.1km2) group of up to 2m high hummocks, a 1m deep kettle hole and a short ridge segment occur at The Old Mill (317600 484900). (B) A group of dissected and streamlined ridges and mounds (up to 10-15m high), and steep-sloped southwest/northeast oriented ridge segments (up to 0.6km long by 8m high) occur 3km further to the northeast from Dunadry (320000 485000) to Ballybentragh (322200 386600). The dissected mounds tend to occur at slightly lower elevations and closer to the central axis of the valley. (C) A 1km2 area of steep sided, sharp-crested 2-3m high hummocks and interconnected 2-6m high ridge segments occurs at Parkgate (323100 388100). The ridge segments show southeast/northwest sub-parallel orientation. The belt contains a disused sand and gravel pit exposing <1m deep, very coarse-grained boulder to cobble gravel. No bedding structures were apparent and up to 20% of clasts were comprised of vesicular basalt containing numerous calcitic zeolites. (D) A cross-valley ridge (up to 6m high by 0.2km long) occurs on the western margin of Doagh village (326300 389500). Four streamlined, dissected ridge segments (up to 4m high by 0.2km long) occur at lower elevations along the valley floor axis 1km further to the northwest amidst a 0.3 km2 flat area located at 60m O.D. The basaltic bedrock topography along the orientation of the belt, exposed in several places e.g. Paradise Bridge (322200 487200), undulates at the same scale as the deposits at Dunadry to Ballybentragh. A lack of exposures and similarity of the bedrock morphology to that of the glaciofluvial deposits means the topography surrounding the identified belt may contain further shallow gravel deposits. Hill and Prior (1968) document striae and three till fabrics occurring to the south of the valley. Their evidence and the orientation of large scale streamlined ridges and drumlins along the margins of the valley indicate a south/north direction of ice pressure during the last glacial period.
Importance:
The glaciofluvial deposits of the Six Mile Water complex are largely intact and in places show clear ice-contact morphology. The deposits indicate that a high piezometric surface existed in the ice-lobe which occupied the Six Mile Water depression during the deglacial period. Streamlined topography along the upper margins of the valley indicates that the area was subject to topographic modification by fast ice flow events during the Late-glacial period. Hummocky , kettled topography e.g. at Old Mill indicates the burial and later meltout of marginal, stagnant, ice by glaciofluvial sediments. The ice-contact ridges at Parkgate provide the best indication that a subglacial conduit operated along the margin of the valley. The deposits demonstrate the control exercised by bedrock topography upon ice pressure at late stages in the deglaciation of the area. Hill and Prior (1968) show that ice pressure during till-forming glacial advance was from an east/west ice divide axis to the south. The orientation of streamlined bedforms and meltwater drainage in the valley is southwest/northeast, possibly indicating a shift in the orientation of the ice divide prior to the streamlining event or channelling of ice flow around bedrock topographic barriers during increased ice velocities.
Interpretation:
A lack of exposures in the deposits limits detailed examination of sediments and reconstruction of the depositional environments. However, based on the steep-sloped morphology of the deposits and their occurrence as a sinuous, localised, valley-parallel belt it is inferred that the deposits are probably associated with ice-contact glaciofluvial deposition in a range of environments: A) subglacial e.g. Parkgate and Dunadry/Ballybentragh steep-sloped ridges, B) ice-marginal e.g. Doagh cross-valley ridge, and C) subareal e.g. the kettle hole and hummocks at the Old Mill. The discontinuous nature of the belt may have resulted from depositional processes or more likely is a result of post-depositional (Holocene) fluvial erosion. Such erosion has resulted in the streamlining and dissection of the deposits located at lower elevations along the valley axis. The deposits are inferred to have been deposited from meltwater associated with the Irish ice sheet. This due to two main reasons: 1) The ridges, hummocks and kettle holes at Parkgate and the Old Mill, preserved above the level of topographic modification by meltwater dissection and streamlining, are small-scale ice-contact features more likely associated with a decaying, Irish ice mass than a larger Scottish ice mass; 2) The surrounding topography shows a streamlined character associated with topographic modification due to the rapid flow of Irish based ice during the last Drumlin forming event. Therefore the valley was occupied by a lobe of Irish ice during the deglacial period. The preservation of the glaciofluvial deposits along a corridor of high energy ice-flow indicates that their formation post-dated this event. The deposits demonstrate that the Irish ice sheet maintained a hydrostatic head of pressure after the drumlin forming event, with sufficient velocity to transport the boulder-sized clasts exposed at Parkgate. The deposits are therefore contemporaneous with the larger esker system at Glarryford, 25km to the northwest (see Key Site 466 - Glarryford). Dardis (1982, 86) documents ice-marginal glaciolacustrine deposits at Carmean, 25km to the northwest, at the northwest margins of Lough Neagh. They are inferred to be associated with a palaeolake level in the Lough Neagh area located at 61m O.D. during the deglacial period. The topographic flat to the northeast of Doagh located at 60m O.D. may represent a Holocene terrace fragment or indicate the presence of a palaeolake level in the valley of circa 57-60m O.D. Both deposits may have been deposited in the same waterbody. The deposits in the Six Mile Water valley would probably have been supplied from the upper valley to the northeast after deglaciation of the lower valley and ponding of a regional lake at 60m O.D.
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:	Gravel, Sand
Relations:	Deglacial sediments, Glacio-fluvial sediment
Geomorph:	esker

Access
Management:
The deposits at Parkgate add significant topographic diversity to this area of the valley. Elsewhere the undulations of the deposits are similar to those in the subjacent bedrock topography. Excavation of the deposits would detract significantly from the intact rural landscape of improved farmland and scattered farm dwellings. The main routeway through the valley (B95) utilises the high ground of the deposits along the northern banks of the river. The elevated, well-drained topography also has a high concentration of archaeological sites including raths, cairns and standing stones.

Access

Management:

The deposits at Parkgate add significant topographic diversity to this area of the valley. Elsewhere the undulations of the deposits are similar to those in the subjacent bedrock topography. Excavation of the deposits would detract significantly from the intact rural landscape of improved farmland and scattered farm dwellings. The main routeway through the valley (B95) utilises the high ground of the deposits along the northern banks of the river. The elevated, well-drained topography also has a high concentration of archaeological sites including raths, cairns and standing stones.

References (3)
Dardis, G.F., 1982. Sedimentological aspects of the Quaternary Geology of South-Central Ulster, Northern Ireland (Thesis), pp.422 Unpublished PhD Thesis, New University of Ulster.
Dardis, G.F., 1986. Late Pleistocene lakes in south-central Ulster, Northern Ireland Irish Journal of Earth Sciences, vol. 7, pp.133-144.
Hill, A.R. & Prior, D.B., 1968. Directions of ice movement in northeast Ireland Proceedings of the Royal Irish Academy, vol. 66 pt. B, pp.71-84.

Record type:	ESCR report
Entered by:	E M Porter

Enlander, I., Dempster, M. & Doughty, P., 2026. Six Mile Water, County Tyrone, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=488. Accessed on 2026-11-08.