ESCR - Fintona Hills Complex - Dromore outwash-moraine system

Earth Science Conservation Review

Summary Full report
Fintona Hills Complex - Dromore outwash-moraine system	Fermanagh, Tyrone

Site number:	497
ESCC:	IS
Locality Type:	Inland exposure, Pit	Status:	TBC
Grid Reference:	H457556,H487582 End(s) of linear site, Not Entered
Google maps:	54.44732,-7.29552
County:	Fermanagh, Tyrone	Council area:	Fermanagh & Omagh District Council
Period:	Quaternary

Site Description
Description:
This area is a discrete unit extending north to south from Syonfin to Dromore (7km), and west to east from Legamaghery (H457556) to Altanaveragh (H487582) (4km). Physiographically the area is contained within the upper Glennamuck valley and comprises outwash spreads, moraines and eskers which cross the valley SSW to NNE. These sediments are generally superimposed upon bedrock and are heavily dissected by meltwater. There is one main exposure. The Legamaghery pit is located at H462554 in a small bedrock basin (<0.5km2) containing a large, mainly disused sand pit (area 0.8ha). There is one small exposure of glaciotectonic contorted clays within a gravel/sand sequence. Facies description This exposure (1.5m high by 8m long) is characterised by vaguely stratified (0.3-0.6m thick) interbeds of sorted, clast-supported pebble gravels (<10cm diameter) and medium sand to clay beds. The latter show glaciotectonic deformation and are composed of well-sorted clast-supported granules, and poorly-sorted granule to pebble (<15cm diameter) facies. Gravel units have transitional contacts and up to 25% of erratics are derived from the Tyrone Igneous Complex. The polymodal sand to clay bed (0.6-1.2m thick) shows both normal and inverse grading. Deformation styles in this unit include: (1) large-scale open fold-type undulations, 0.4m high by 0.5m wide. This scale of folding also affects the surrounding gravel beds. (2) cm-scale normal and reverse faulting. This often affects the finer silt and clay laminae, especially near the strike axes (090§-270§) of these 'folds'. (3) Large-scale (1m long, displacement 0.6m) high angle listric push faulting, mainly by shearing through clay laminae. Strike is approximately 100§-280§. (4) Lateral elongation or boudinage-type extension of fine-grained lamination. (5) Soft sediment-style dm-scale compression of silt/clay beds. This occurs to the left hand side of the exposure where the unit is 20-30cm thick. The unit remains intact during deformation. Compression strike is 060§-240§. (6) Loading-type deformation, seen in the middle of the exposure, with vertical displacement of homogenised clay/silt beds. (7) Antithetic clay layer 'rolling' around less deformable material, as seen to the right hand side of the exposure. This deformation style also covers gravelly lenses included within the clay/silt unit by deformation of these sediments over the top of the gravel lens. (8) 'Zigzag' deformation of the contact between the clay/silt unit and the subjacent gravels. Facies interpretation Sorted gravel and silt beds record deposition in an impounded water body. Deformation has meant that there is little evidence for deposition direction but it is likely to have been similar to that of later deformation. Strike direction of folds and faults indicate that glacial readvance, causing glaciotectonic deformation, was north to south (approximately 000§-180§), but this deformation was proglacial rather than subglacial. Elevated pore water pressure ahead of the advancing glacial freezing front (McRoberts and Morgenstern, 1975) probably encouraged rapid groundwater movement. Sediment deformation style implies that the sediment mass was largely unfrozen, thus that free water was available. A physiographic basin is also likely to have been a groundwater sink. Lack of water escape structures favours the free movement of groundwater trapped beneath the silt/clay aquiclude to elsewhere in the system. This is evidenced by the variable-thickness and interbedded nature of the silt/clay unit. Lack of morphological evidence at this location for glaciotectonic deformation and ice readvance (i.e. moraines) may be due to the relatively distal nature of deformation in this exposure, and erosion by meltwater which overdeepened the Glennamuck river valley. Moraines showing glaciotectonic deformation of gravels consistent with ice push from the north are located 2km north of this exposure at Lackagh (H456572; H461570).
Notes:
For site specific information on other sites within the Fintona Hills Complex 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 498 - Fintona Hills Complex - Newtownsaville Esker For overview information and references on the Fintona Hills Complex see the following site: Key Site 484 - Fintona Hills Complex - Overview 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 This site is also a Site of Local Nature Conservation Importance. See Key Site 725 - Dromore.

Keywords
Rocks:	Gravel, Sand
Relations:	Glacial deposit, Glaciotectonic
Geomorph:	moraine, outwash


Record type:	ESCR report
Entered by:	E M Porter
Last updated:	6 Jun 2005

Enlander, I., Dempster, M. & Doughty, P., 2026. Fintona Hills Complex - Dromore outwash-moraine system, County Fermanagh, Tyrone, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=497. Accessed on 2026-11-06.