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Earth Science Conservation Review
| Moneymore Complex | Tyrone |
| Site number: | 481 | ||
| ESCC: | IS | ||
| Locality Type: | Inland exposure | Status: | TBC |
| Grid Reference: | H28593898,H28493838 Corners of site, Not Entered | ||
| Google maps: | 54.29856,-7.56224 | ||
| County: | Tyrone | Council area: | Fermanagh & Omagh District Council |
| Period: | Quaternary | ||
| Site Description | |
|---|---|
| Highlights: | |
The Moneymore complex is one of the few lowland locations recording the presence of fine-grained, glaciolacustrine sediments in N. Ireland. The areal distribution of ice-marginal glaciolacustrine deposits along the western margin of the Lough Neagh lowlands, and the palaeoflows from these deposits (Dardis, 1982), show that the area records the approximate position of the western margin of the ice mass occupying the Lough Neagh basin at the end of the last glacial period. The basin thus formed one decay centre for ice in the east of the province. Ice and snow melt in the uplands (Fintona Hills) to the west provided meltwater for limited erosion, transport and deposition of glaciolacustrine detritus in an ice-marginal waterbody ponded at 60m O.D. in the lowlands. Subsequent falls in lake levels was followed by partial dissection of the deposits. The undulating nature and deranged nature of the western Tyrone drumlin field also resulted in the formation of localised ice-proximal water bodies and the deposition of small glaciolacustrine sequences possibly at a slightly later phase. | |
| Description: | |
The Moneymore unit is subdivided into two subunits for descriptive and interpretative purposes. Most of the large exposures described have been recorded by Dardis (1982). A re-examination of the field area has shown that the majority are no longer exposed to the same degree. The description and interpretation presented here is based largely on the work of Dardis (1982, 1985, 1986). The deposits are described from north to south. 1. Moneymore composite delta A 4km2 area of stratified deposits occurs to the north and west of Moneymore, Co. Tyrone (285800 383400) along the valley axis of the north/south oriented Ballymully river valley from Lecumpter (285900 389800) to Turnaface (284900 383800). A 0.5km2 topographic flat occurs at 70m O.D. from Lecumpter to Reuben's Glen Bridge (285800 388800). Immediately south, around Carmean (285800 387600), a 500m wide belt of rolling topography is cut by west/east oriented minor meltwater channels. A small-scale, water filled, enclosed depression occurs near Quilly at 285900 386900. This deposit reaches 85m O.D. in the vicinity of Larrycormick Hill (285300 385700), where it is approximately 50m in thickness. The belt of deposits continues south to Boheroy Cottage (285300 384500) and Turnaface where it has been extensively dissected by generally west/east oriented meltwater channels. Carmean exposure Dardis (1982) documented a 35m long by 10m deep exposure at Carmean (285800 387500), occurring at 61m O.D. which consisted of two principal LFAs. LFA1 consists of 5-8m of steeply-dipping, planar cross-bedded gravel, parallel laminated gravel and minor climbing ripple sequences. Palaeoflow was to 020§N. LFA2, which overlies LFA1 above a sharp contact, consists of 1-2.5m of horizontally bedded pebble gravel containing occasional lenses of massive sand. Boheroy Cottage exposure Dardis (1982) recorded a fining upward sequence of planar cross-bedded gravel at Boheroy Cottage which also fined northeastwards into planar cross-bedded sand. The exposure was in the flank (285200 384600) of an isolated, steep-sided mound which reached 57m O.D. The existing exposure (1.5m deep) shows small-scale extensional faulting to the north along the flank of the mound adjacent to a NW/SE trending meltwater channel. Clasts consisted predominately of red granite (>80%), with smaller amounts of chalk, flint, basic igneous and quartzite. Palaeoflow, from cross bedding orientation, was to 270-300§N. Moneymore exposure A number of poor exposures recorded by Dardis (1982) occurred west of Moneymore (285800 383400), in mounds located at the eastern end of meltwater channels which form part of the Carndaisy Glen channel network. A 4.5m deep exposure contained two principal LFAs. LFA1 consists of 2-3m of horizontally bedded gravel and is separated from the overlying LFA2 by a sharp contact. LFA2 consists of small-scale cross-bedded gravel and sand. Palaeoflows in both units were to 110§N. Turnaface exposure An exposure at Turnaface (284900 383800) showed a 6m deep sequence of interbedded large-scale planar cross-bedded sand and pebble gravel and occasional beds of silt overlying 2-3m of massive, sandy diamict which contained occasional clasts. Cross-bed orientation indicates a northward palaeoflow, into a ponded waterbody occurring at 57-60m O.D. (Dardis, 1982). At an adjacent location an exposure in a disused commercial quarry shows a 10m deep sequence of two LFAs. LFA1 consists of interbedded planar cross-bedded well-sorted sand and pebble gravel dipping at >15§ to 030§N. The sand contains minor ripple sequences which fine laterally (towards 030§N) into thinly-bedded silty sand. Palaeoflow based on cross-bed orientation and ripples was to 030§N. LFA2 is 70cm deep and consists of small-scale cross-bedded sand and silty sand. Palaeoflow was to 045-050§N. Clasts consist predominately of sandstone (50-60%) with smaller amounts of red granite and basic igneous erratics together with an outsized (30cm a-axis) clast of flinty chalk. 2. Annahavil Delta A north/south oriented linear deposit occurring to 105m O.D. occurs from Derryragan (280700 371600) to near Cloughcor (278700 366800), a distance of 3.5 km. The deposit topography is predominately rolling, and is cut by numerous southeast/northwest oriented 5 -10m deep channels. The eastern slopes are steep (>20§) in places, especially around Drumard (281000 368500). The eastern, generally north/south oriented margins of the deposit merge with several east/west oriented beaded, steep-sided linear ridges of <25m relief. Two exposures in the deposit are documented by Dardis (1982). Annahavil Hill exposure The exposure at Annahavil Hill, located on the western flank of the deposit consisted of two principal LFAs (Dardis, 1982). LFA1 showed a lateral facies transition northwards from large-scale, low angle (15-30§) planar cross-bedded sand and pebbly sand, to massive sand with occasional isolated clasts, to massive sand containing clay laminae occurring in channels (5-10m broad), to low angle, rippled cross-stratified sand. Palaeoflow, based on cross bedding, was to 005-015§N. Overlying LFA1, 1-3m of LFA2 consisted of parallel laminated sand, silt, clay and lignite clasts. At the northern extremity of the exposure massive silty-sand, filling bowl-shaped depressions up to 3m deep forms the upper component. Derryragan exposure The exposure recorded by Dardis (1982) at Bloomhill, is renamed as Derryragan. It is located near the merging of the Annahavil deposit and a flat area bordering it immediately to the north. One LFA consisted of a coarsening upwards, 10m thick facies sequence, consisting of horizontally bedded and rippled (A and S type) sand, small-scale planar cross-bedded sand and horizontally bedded gravel. Palaeoflow, based on cross-bedding, was to the northeast. Bloomhill exposure At Bloomhill, a 10m deep section in a disused pit is located in the flank of a mound at 100m O.D. One LFA is exposed, consisting of well-sorted, large-scale planar cross-bedded to ripple cross-bedded sand and silty sand. Several beds contain discontinuous high concentrations of lignite clasts which are up to 3-4cm in length. Palaeoflow, from cross-bedding orientation, was between 10-40§N. 3. Other deposits Ardgivna exposure At Ardgivna (279200 364200) Dardis (1982) recorded a section occurring at 71m O.D. which consisted of interbedded parallel-bedded and ripple laminated (A, B and S types) silt and clay beds and diamict units. One diamict varied from 0.2- 2.0m thick and was 27m long. It showed well-developed bed-parallel shears and inverse to normal and coarse-tailed grading of clast size. The major portion of the glaciolacustrine sequence was draped over the diamict, which also overlies drape laminae. Palaeoflows of the diamict units, from till fabric measurements, were to 270§N. Tullyaran exposure An exposure at Tullyaran (275800 367500) occurred in a mound up to 100m O.D., 5km south west of Annahavil (Dardis, 1982). The section consisted of one LFA. It consisted of crudely-stratified, coarse-grained gravel which graded laterally into large-scale planar cross-bedded gravel containing complex sequences of gravel and small-scale laminated silt drapes. The planar cross-bedded gravel has undergone compressional folding and faulting. Palaeoflow, from cross-bedding, was to 230§N. Coalisland exposure Poor exposures are documented by Dardis (1982) near Coalisland (284300 367000) from two small-scale terraces extending southeastwards from just north of the town at 61 and 30m O.D. The sand was fine grained with small-scale cross-bedding. Recent investigation shows a poor exposure located at 283300 367700, at 70m O.D. 0.5km northwest of the exposures documented by Dardis (1982). It occurs in a hollow between two streamlined ridges. The section shows 2m of a generally coarsening upward sequence of low-angle planar cross-bedded well sorted sand interbedded with sandy pebble gravel. Palaeoflow, based on cross-bedding orientation, was to 340§N. Several other exposures in localised low relief mounds are, probably part of the same deglacial complex. These are recorded at Lowertown (282500 362400) (Dardis, 1982) and at Moygashel (280700 359800), south of Dungannon (Mc Cabe, pers. comm.). | |
| Importance: | |
The deposits of the Moneymore Complex are scientifically important for the following reasons: A) Comparisons with information from other areas in the region, e.g. Fintona Hills, Ballinderry valley and Moyola valley, show that the glaciolacustrine deposits document the final stages of ice melt from one of the provinces major ice decay centres, the Lough Neagh basin. B) The ice-push glaciotectonic forms observed at Tullyaran by Dardis (1982) show that at late stages in the decay of the ice-mass, the ice-margin was active in places and may have been temporarily advancing. C) Erratic carriage demonstrates detritus supply from two principal directions. Red, coarse grained granite clasts from the Tyrone Igneous complex indicates meltwater supply from the highlands to the west whereas the lignite clasts observed at Bloomhill have been reworked from sediments formed from the glacigenic erosion of areas in the east of the Lough Neagh basin. | |
| Interpretation: | |
The interpretation outlined below is based mainly on the detailed work and conclusions reached by Dardis (1982, 1985 and 1986). 1. Moneymore delta The flat-topped valley fill occurring from Lecumpter as far as the most northerly east/west oriented cross-valley meltwater channel (Reuben's Glen) is inferred to represent the top surface of a glaciolacustrine delta deposited from an ice margin located 3km due south at Quilly. The flat-top around Cranny gives a palaeolake level at around 70m O.D. The well-sorted, fine-grained sediments at Carmean, 2km downvalley, are inferred from the large-scale planar cross-bedded foresets and fluvial topsets to represent ice-marginal deltaic deposition into a palaeolake ponded at 61m O.D. Kettle holes, thrust-faults and palaeoflows recorded in the deposits at Carmean, suggest that this part of the delta was deposited in an ice-proximal location, from ice located immediately to the south of or near Larrycormick Hill. Sediments recorded at Turnaface, Moneymore and Boheroy Cottage are inferred however to represent extramarginal deposition, from meltwaters entering a lake ponded at 60m O.D. from the highlands to the west. This is suggested from the palaeoflow patterns recorded in the sediments and the high proportions erratics from the Tyrone Igneous complex (granite, basic igneous) and Sperrin uplands (sandstone) present in these sediments. The high degree of sorting, bed geometry and presence of draped rhythmites indicates that the sediments accumulated subaqueously. The deposits around Moneymore therefore represent the aggradation of deltaic sediments entering a lake from two principal directions i.e. from the south and west. It is inferred that the deposits represent the remnants of a composite delta, formed as a result of ice backwastage south and southwestward towards the area of present day Lough Neagh and into the Fintona Hills uplands, and the ponding of meltwater between the ice margins and rising ground of the surrounding topography. Meltwater and sediment was supplied from both directions and resulted in the formation of ice-marginal and extra marginal deltas which probably coalesced where sediment sources where in close proximity. The upper surface of the deposit occurs to approximately the same height i.e. 60m O.D. throughout. Aggradation is inferred to have occurred from meltwater sources into a lake impounded in a proglacial location to at least 70m O.D. (height of flat-top at Cranny) at one stage. After drainage of the lake, fluvioglacial erosion, principally by meltwater originating in the highlands to the west, resulted in extensive dissection of the deposits, resulting in a discontinuous, rolling belt of deposits. 2. Annahavil Hill Delta The facies arrangement at Annahavil Hill suggests a deltaic/distal lacustrine transition sequence whereby a well-sorted, fine-grained lower deltaic component is overlain by a finer grained horizontally bedded lacustrine sequence. The shallow angle of the deltaic cross-bedding and nature of the surrounding topography indicate that deposition occurred into a shallow proglacial lake ponded at 110m O.D. from; A) low energy subglacial sources located at several points along the western edge of an ice-margin, B) remobilisation of these deposits as mass flows down delta foreslopes and C) ice-bergs, calved from the ice margin. The linear, beaded morphology of the sharp-crested, sub-parallel ridge segments and field relations to the deltaic sequence suggest they represent esker sediment supply channels, although no exposures record the internal sediment geometry. The steep ice-contact slopes at Drumard indicate the possible location of the ice margin during aggradation of the delta to 110m O.D. It is inferred from regional ice-margin retreat patterns (see Key Sites 473 - Dunnamanagh, 474 - Foyle, 475 - Glenelly) that the 110m O.D. lake into which the Annahavil Hill delta prograded formed at a later date than the Carmean (c. 61m O.D.) lake level. It was also of more regional extent than the earlier lake level, with glaciotectonised ice-marginal deposition at Tullyaran 4km to the southwest occurring at the same elevation. The two deposit belts at Moneymore and Annahavil record the location of the ice margin at successive times during the same period of ice wastage in the province's lowlands. 3. Other deposits The deposits at Ardgivna and at Coalisland (at 283300 367700), from their localised nature and shallow angle cross-beds, are inferred to represent deposition into small waterbodies located in inter-drumlin hollows. The extra-marginal terraces documented by Dardis, 1982 at Coalisland are associated with input from regionally traceable northwest/southeast oriented meltwater channels into localised ice-marginal waterbodies. The fine-grained, well-sorted sediments found in the majority of the locations in this unit represent the final sediment deposited from the decaying ice mass. Summary The deposits of the Moneymore complex as a whole record glaciolacustrine deposition at the margin of a largely stagnant ice-mass situated in the Lough Neagh lowlands. The wastage of the ice mass and ice and snow melt from highland areas to the west provided meltwater and detritus which became impounded along the ice margin. Glaciolacustrine sediments were deposited along the ice margin and at the end of the meltwater channels from the highlands. The heights of the upper surfaces of the sediments indicate that two extensive ice-marginal lake levels of 61m and 110m O.D. existed in the proglacial area. Where local (e.g. drumlin or bedrock) topography allowed, smaller localised levels existed before (e.g. 70m at Cranny) and after the ponding of meltwater at these levels, recorded by spatially restricted glaciolacustrine sequences. Later drainage of the lakes resulted in the subaerial erosion and dissection of the deposits. | |
| 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 This site is also a Site of Local Nature Conservation Importance. See Key Site 740 - Moneymore. | |
| Keywords | |
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| Rocks: | Gravel, Sand |
| Relations: | Deglacial sediments, Glaciolacustrine deposit |
| Geomorph: | drumlin, ice-marginal lake, meltwater channel |
| Measurements | |||||
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| Length: | Width: | Height: | |||
| Depth: | Area: | 4km2 | |||
| Access | |
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| Management: | |
The landforms of the unit are situated in the lowland, undulating topography of the western Tyrone drumlin field, which tends to lessen their visual impact upon local topography. However most of the deposits have undergone post-depositional erosion by meltwater and are preserved as remnant spreads and ridges. No examples of classic landforms occur in the region. However an excellent local example of ice-contact topography and a subglacial/proglacial landform association is present at Drumard. Commercial sand and gravel extraction has now largely ceased in the area, and many of the pits are now in advanced stages of natural recovery with the subsequent loss of sediment exposures but an increase in the biodiversity of a lowland area dominated by improved farmland. | |
| Uses | |
| Uses: | Farmland |
| References (3) | |||
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| 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., 1985. Genesis of Late Pleistocene Cross-Valley Moraine ridges, South-Central Ulster, Northern Ireland Earth Surface Processes and Landforms, vol. 10, pp.483-495. | |||
| Dardis, G.F., 1986. Late Pleistocene lakes in south-central Ulster, Northern Ireland Irish Journal of Earth Sciences, vol. 7, pp.133-144. | |||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Moneymore Complex, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=481. Accessed on 2026-11-06. |
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