ESCR - Fintona Hills Complex

Earth Science Conservation Review

Summary Full report
Fintona Hills Complex - Overview	Fermanagh, Tyrone

Site number:	484
ESCC:	IS
Locality Type:	Inland exposure	Status:	TBC
Grid Reference:	H263516,H551620 End(s) of linear site, Not Entered
Google maps:	54.41276,-7.59491
County:	Fermanagh, Tyrone	Council area:	Fermanagh & Omagh District Council
Period:	Quaternary

Site Description
Highlights:
The Fintona Hills Complex shows a variety of ice marginal and subglacial landforms dating from the period of ice thinning when the main ice mass split up over the axis of the Fintona Hills. This resulted in the separation of Omagh Basin and Clogher/Tempo valley ice masses to the north and south respectively. Ice mass decay was then topographically controlled. Omagh Basin ice actively retreated from the uplands and deposited a range of marginal sediments, including kame terraces, outwash surfaces, moraines and eskers. These sediments generally record water outflow towards the east and northeast. This implies that ice blocked western meltwater outlets through the Lower Lough Erne Basin, and that the ice mass profile was probably steeper in the west than in the east. On a regional basis, this is evidenced by distinctive push moraines to the east of the Omagh Basin (see Key Site 479 - Murrins) and a lack of morainic evidence to the west. There are few exposures in the Fintona Hills Complex, but they generally confirm this hypothesis.
Description:
The solid geology of the Fintona Hills Complex is dominated by Devonian-age ORS and associated conglomerates (Wilson, 1972). Conglomerate beds are generally oriented northeast-southwest and comprise the upland rib of Brougher Mountain (H350528) and the area to the east of Eskragh. Also aligned northeast-southwest are major Caledonian-age faults (Ryan et al., 1995) which split the area into large upland blocks, as around Tattymoyle (H415562). Fault alignment has had a major impact on deglacial history and topography. Tertiary-age dolerite dykes, aligned northwest-southeast (Wilson, 1972), have had very little impact on deglacial history or landscape characteristics. Glacial sediments generally occur below 170m a.s.l., but reach locally 190m in upland bedrock basins (e.g. near Dromore). The Fintona Hills Complex can be split into 5 areas on the basis of landform morphology, sedimentary characteristics and inferred depositional setting. These areas are: (1) Ballinamallard esker, (2) Crockfadda outwash-moraine system, (3) Dungoran kame-esker- outwash system, (4) Dromore outwash-moraine system, and (5) Newtownsaville esker. For site specific information see the following sites: Key Site 494 - Fintona Hills Complex - Ballinamallard Esker Key Site 495 - Fintona Hills Complex - Crockfadda outwash-moraine system Key Site 496 - Fintona Hills Complex - Dungoran kame-esker- outwash system Key Site 497 - Fintona Hills Complex - Dromore outwash-moraine system Key Site 498 - Fintona Hills Complex - Newtownsaville Esker
Importance:
The Fintona Hills Complex is of high value by virtue of its location, extent, and morphological and sedimentary characteristics. This is because: A) The association of eskers with outwash and moraines indicates that subglacial conveyance of material to the ice margin was active and dynamic. B) The juxtaposition of moraines, outwash and kames terraces indicates a highly dynamic ice margin. It also indicates very localised sediment activity. C) Subglacial eskers at Ballinamallard-Trillick and Newtownsaville are probably late features, post-dating ice separation over the Fintona Hills. The partial tunnel valley position of the former system is not common in Northern Ireland. D) Sand and gravel landforms in the Glennamuck valley resulted from both Omagh Basin and Clogher/Tempo valley ice. A local ice mass centred over Crocknatummoge (and retreating east towards Eskragh) may also have influenced this area. These ice masses were responsible for glaciotectonic deformation of Glennamuck sediments, and may have periodically blocked the northern valley outlet. E) Kame terraces as around Dungoran have not been often identified in Northern Ireland.
Interpretation:
The only existing literature on this area (Charlesworth, 1924) does not refer specifically to any location or landform. Instead, Charlesworth (1924, pp. 272-5) hypothesised that a regular series of retreat moraines were deposited along the north side of the Fintona Hills related to the westward withdrawal of the Tyrone Glacier towards Lower Lough Erne. However, this view is not wholly substantiated by morphological and sedimentary field evidence. This is due mainly to the complex juxtaposition of a range of ice marginal sedimentary environments, which means that it is unlikely that recessional moraines of the type described by Charlesworth (1924) are present. Sand and gravel landforms are tightly constrained against the northern slopes of the Fintona Hills, and change rapidly in characteristics over short distances. Dynamic sedimentary environments of this type can be generated by the deposition between a lowland ice lobe with an adjacent bedrock upland. This interaction determines location of possible ice pinning, location of ponded water and outflow direction. Other characteristics of this area have major implications for regional deglaciation patterns. The juxtaposition and complexity of proglacial and ice-marginal sediments (kames, outwash and moraines) does not necessarily indicate either a fast rate of westward ice retreat, or that a 'Tyrone Glacier' still occupied areas of higher ground. It appears that these sediments were formed as ice oscillated on the slopes of the Fintona Hills, causing localised and short-lived ponding events. This is evidenced partly by (1) the dominance of post-depositional meltwater erosion of all landform types, (2) sediment continuity within each individual exposure (i.e. at Syonfin), and (3) the commonness of a(t) imbrication, indicating unidirectional and shallow water deposition. This deposition also appears to have been 'forced' by ice-marginal processes when the ice was in interaction with other landscape features. There is a lack of deglacial evidence on higher ground and elsewhere within the Omagh Basin. This implies that sand and gravel, or comminuted debris, entrained within the glacier was not disseminated throughout the ice mass but rather ice-marginal in location, therefore probably related to specific ice-marginal processes such as shearing. Evidence for both (1) clean ice, and (2) ice marginal activity is seen in the Fintona Hills Complex and elsewhere in the Omagh Basin (see Key Site 479 - Murrins). In more detail, this area shows local differences in emplacement processes of (1) subglacial eskers, and (2) ice marginal moraines, kames and outwash. Eskers are generally well-defined and morphologically distinct in the landscape. The Ballinamallard-Trillick esker, mostly contained in a bedrock-cut channel, implies high initial hydraulic pressure during the incision of the 'N-type' tunnel valley. Similar tunnel valleys infilled with subglacial sand and gravel have been described from northern Canada by Brennand and Sharpe (1993). Tunnel valleys, in focusing meltwater activity, also means that eskers may be erosional remnants and not original features, and may also be associated with subglacial sand and gravel terraces and beads (i.e. Gorrell and Shaw, 1991; Brennand and Sharpe, 1993; Brennand, 1994). Dissipation of the tunnel valley morphology to the east of this region, and the association of eskers with moraines around Crockfadda, implies that this landform assemblage may be contemporaneous (cf. Gorrell and Shaw, 1991). This situation contrasts with that of the Newtownsaville esker where a bedrock channel is not provided and the esker does not have a dominant climbing component. Overall orientation of the Newtownsaville esker implies a strong substrate control on the nature and direction of esker deposition. Sedimentary evidence at Eskragh confirms that this is a subglacial feature deposited under closed tunnel conditions. This is also evidenced by the hypothesis of helicoidal water flow, characteristic of water flow in the subglacial environment (Shaw and Freshauf, 1973). This evidence implies that changes in the nature of the substrate, or location of bedrock (topographic) obstacles, will have a major effect on esker morphology and characteristics. East of Newtownsaville, the esker changes dramatically from west-east trending to south-north trending, following the 140m contour west of the bedrock upland around Garvaghy (H560599) and terminates in an area of hummocky moraine around Brackagh. Furthermore, this relationship implies that the ice cover was fairly thin and responsive to substrate obstacles. Ice-marginal features dominate in the area south of Fintona around Dungoran and Dromore. This is not surprising since there is sedimentary evidence for ice-marginal activity of both Omagh Basin ice in the lowlands and Fintona Hills ice occupying the Glennamuck valley. There are several aspects to this supposition. Firstly, it is notable that erratics from the Tyrone Igneous Complex occur in both the Syonfin and Lagamagery exposures, both of ice-marginal origin. This contrasts markedly with the ORS-dominated subglacial esker sections at Trillick and Crockroe. This may be due to (1) focusing of local subglacial debris in a major subglacial drainage conduit (tunnel valley), or (2) differences in the location of carriage within the glacier. Further-travelled debris might be carried englacially having been earlier sheared upwards from the subglacial zone by ice marginal activity, or reworked from older sediments, although this is unlikely. The record of ice-marginal activity also differs between the moraines supplied by Omagh Basin feeder eskers from the west, and the ice readvance-age glaciotectonic deformations resulting from ice occupying the Glennamuck valley. Readvance activity is inferred mainly from sedimentary rather than morphological evidence. Secondly, the Syonfin exposure records ice push from the south, whereas the Legamaghery exposure records activity from the north. This apparent contradiction can be accommodated by rapid changes in ice margin location related to these different ice masses. It is not clear whether Omagh Basin and Clogher/Tempo valley ice separated completely over the Fintona Hills, especially in linking valleys such as the Glennamuck col, or that separation was synchronous across the Fintona Hills. The general lack of morphological evidence for ice-marginal events at this time may be due to the nature of the ice masses after separation. They are likely to have been composed of both stagnant and active components. Stagnant ice megablocks may have existed around Meencrim (see earlier) and may have directed meltwater drainage and deflected ice activity. Furthermore, a lack of ice-marginal moraines may be due to clean ice. The interaction of different ice masses is also inferred from the carriage of limestone blocks across the Fintona Hills watershed to Crocknaconspody. This may relate to glacial lake drainage south to north from an impounded water body in the upper Tempo Valley (see Key Site 485 - Tempo Valley). The following sequence of events in the Fintona Hills Complex is suggested on the basis of the geomorphic and sedimentary evidence outlined above. It is notable that this sequence appears to be far more dynamic than those operating in lowland areas such as the Clogher Valley. 1) Late Devensian iceflow northeast to southwest. This is inferred from the direction of Rogen moraines occupying lowland areas of the Omagh Basin to the north. There is a general lack of erosional or depositional evidence for ice flow direction over the Fintona Hills at this time but striae on Brougher Mountain record ice flow to the southeast (Charlesworth, 1924). 2) Ice break-up over the Fintona Hills. Ice margins retreated north (Omagh Basin ice) and south (Clogher/Tempo valley ice). This retreat was probably asynchronous, especially through cols, i.e. the Glennamuck valley. Ice may also have occupied local areas within the Fintona Hills, such as around Crocknatummoge (H475596). 3) Northward Omagh Basin ice retreat. Ice was still present over Ballyreagh and Brougher Mountain (see Key Site 485 - Tempo Valley). The Ballinamallard-Trillick tunnel valley was probably incised at this time as the hydraulic gradient changed direction due to the change in ice mass shape as it split up. West to east esker climbing implies a high gradient existed, thus infers an asymmetric ice sheet profile. Esker feeding into moraines and outwash around Crockfadda infers that this area was deglaciated. Ice was still present around Crockroe, and may have helped support the high level sediment assemblage. 4) Deposition of Legamaghery outwash. The sand and gravel features of the Glennamuck valley were deposited from the south or southeast by ice retreating into the Clogher Valley. This ice retreated from moraine positions around Altanaveragh, possibly fed by the esker near Eskernahool (H483567), to the local depocentre around Legamaghery. Omagh Basin ice probably blocked the northern outlet of the Glennamuck valley. 5) Newtownsaville esker deposition. This is probably synchronous with the clearance of Clogher Valley ice from the Dromore area. Eastward retreat of the northern ice margin from Syonfin to Altanaveragh caused a change in the dominant pressure gradient, and subglacial drainage was discharged eastward, depositing this esker. Ice was also fairly thin and responsive to bedrock obstacles. This ice mass was probably pinned over Crocknatummoge. 6) Deformation of Legamaghery sediments. This deformation was effected by Omagh Basin ice extending from Crockroe to Syonfin. Emplacement of the Crockroe esker also took place at this time. Synchronous ice marginal activity is characteristic of a readvance glacial stage, and may be related to a temporarily-cooler climate. 7) Dungoran kame deposition. Kame terraces accumulated against the Fintona Hills prior to Omagh Basin ice retreat south of Fintona. The Glennamuck valley was probably blocked at this time by Crocknatummoge ice (see point 5). 8) Syonfin outwash deposition. This is associated with both eskers and moraines of Omagh Basin ice from the west, and the presence of Crocknatummoge ice to the south. The latter may have contributed meltwater to the overdeepened Glennamuck valley. 9) Ice retreat northwards from the Fintona Hills. Residual ice around Eskragh may have focused meltwater erosion resulting in the clear dissection of the esker ridge. 10) Postglacial landscape development, including peat deposition and alluviation.
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:	Glacial deposit
Geomorph:	esker, kame terrace, moraine, outwash

Measurements
Length:		Width:		Height:
Depth:		Area:	120km2

Access
Management:
This area has generally high morphological intactness. Existing sand and gravel pits are localised and are often quite efficient in production (i.e. Eskragh) and do not encroach on regional landscapes. Specific aesthetic attributes of this area includes: 1) The length and continuity of the Ballinamallard-Trillick esker. It is also well defined in the landscape, especially around Kilskeery, and ridge orientation, kettleholes and small loughs give landscape diversity. The incised bedrock channel associated with this esker is also important and juxtaposes sand and gravel against bedrock. 2) The Dungoran kame terraces are well-preserved and form a distinct landscape component. 3) The Glennamuck valley is a well-contained physiographic area constrained between bedrock uplands, and acts as the link between the Omagh Basin and the Clogher Valley. 4) The Newtownsaville esker is a very important landscape component. Despite a high degree of local despoilment (see above), many of the esker ridges are still intact and well-defined.

Access

Management:

This area has generally high morphological intactness. Existing sand and gravel pits are localised and are often quite efficient in production (i.e. Eskragh) and do not encroach on regional landscapes. Specific aesthetic attributes of this area includes: 1) The length and continuity of the Ballinamallard-Trillick esker. It is also well defined in the landscape, especially around Kilskeery, and ridge orientation, kettleholes and small loughs give landscape diversity. The incised bedrock channel associated with this esker is also important and juxtaposes sand and gravel against bedrock. 2) The Dungoran kame terraces are well-preserved and form a distinct landscape component. 3) The Glennamuck valley is a well-contained physiographic area constrained between bedrock uplands, and acts as the link between the Omagh Basin and the Clogher Valley. 4) The Newtownsaville esker is a very important landscape component. Despite a high degree of local despoilment (see above), many of the esker ridges are still intact and well-defined.

References (12)
Brennard, T.A., 1994. Macroforms, large bedforms and rhythmic sedimentary sequences in subglacial eskers, south-central Ontario: implications for esker genesis and meltwater regime Sedimentary Geology, vol. 91, pp.9-55.
Brennard, T.A. & Sharpe, D.R., 1993. Ice-sheet dynamics and subglacial meltwater regime inferred from form and sedimentology of glaciofluvial systems: Victoria Island, District of Franklin, Northwest Territories Canadian Journal of Earth Science, vol. 30, pp.928-944.
Charlesworth, J.K., 1924. The glacial geology of the north-west of Ireland Proceedings of the Royal Irish Academy, vol. 36 pt. B, pp.174-314.
Gorrell, G. & Shaw, J., 1991. Deposition in an esker, bead and fan complex, Lanark, Ontario, Canada Sedimentary Geology, vol. 72, pp.285-314.
Hampton, M.A., 1975. Competence of fine-grained debris flows Journal of Sedimentary Petrology, vol. 45, pp.834-844.
Kurimo, H., 1980. Depositional deglacial forms as indicators of different glacial and glaciomarginal en.
McDonald, B.C. & Vincent, J.S., 1972. Fluvial sedimentary structures formed experimentally in a pipe, and their implications for interpretation of subglacial sedimentary environments Geological Survey of Canada Paper, vol. 72-27, pp.30.
McRoberts, E.C. & Morgenstern, N.R., 1975. Pore water expulsion during freezing Canadian Geotechnical Journal, vol. 12, pp.130-141.
Ryan, P.D., Soper, N.J., Snyder, D.B., England, R.W. & Hutton, D.H.W., 1995. The Antrim-Galway Line: a resolution of the Highland Border Fault enigma of the Caledonides of Britain and Ireland Geological Magazine, vol. 132, pp.171-184.
Shaw, J. & Freshauf, R.C., 1973. A kinematic discussion of the formation of glacial flutings Canadian Geographer, vol. 17, pp.19-35.
Warren, W.P. & Ashley, G.M., 1994. Origins of the ice-contact stratified ridges (eskers) of Ireland Journal of Sedimentary Research, vol. A64, pp.433-449.
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. Fintona Hills Complex - Overview, County Fermanagh, Tyrone, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=484. Accessed on 2026-11-06.