The use of a cultural overlay in defining Landscape Character Areas (LCAs) means that they frequently subdivide natural physiographic units. It is common therefore for significant geomorphological features to run across more than one LCA. It is also possible in turn, to group physiographic units into a smaller number of natural regions. These regions invariably reflect underlying geological, topographic and, often, visual continuities between their component physiographic units, and have generally formed the basis for defining landscape areas such as AONBs. It is essential therefore, that in considering the 'Geodiversity' of an individual LCA, regard should be given to adjacent LCAs and to the larger regions within which they sit. In the original Land Utilisation Survey of Northern Ireland, Symons (1962) identified twelve such natural regions.
This LCA lies within the region described as the Central Uplands of Tyrone and Fermanagh. This area is defined in the north by the fault-guided scarp that forms the southern edge of the Sperrin Mountains. Below this are plateau lands that decrease in height and complexity to the south, before rising again to the lower slopes of Slieve Beagh. Below ca 350m the landscape is dominated by thick drift deposits, including prominent drumlin fields, dead ice features and glaciofluvial deposits - often capped by blanket peats. Some hills rise above the general level of the plateau, most notably the basalt-capped outlier of Slieve Gallion. The southwestwards trending Clogher Valley effectively divides the southern section of the upland into two blocks, one lying between Tempo and Pomeroy and the other centred on Slieve Beagh.
The Carrickmore Hills are a distinctive upland landscape to the south of the Sperrins. The area is underlain by a variety of igneous rock that form an elevated plateau, with numerous steep, rocky granite summits, including Evishanoran Mountain, Cregganmore and Loughmacrory Hill. Parts of the plateau are raised bog and there are numerous rounded loughs, particularly in an area known as The Murrins. The land form of the plateau is undulating, with ridges of glacial moraine and rocky outcrops giving the landscape an irregular pattern and scale. The summits have a more irregular, rocky landform and distinctive, irregular silhouettes that are landmarks for miles around. Many of the ridges of moraine have been carved by quarries, particularly on the edges of the plateau. Many of the quarries are small in scale, but nevertheless leave substantial scars and hollows. The upland summits are relatively small in comparison to the surrounding uplands and their distinctive rocky skylines are extremely sensitive to change. The uplands are a landmark from a wide area and even small changes, due to mineral extraction, built development or the introduction of forestry would have a detrimental impact. The most obvious current pressure is from sand and gravel quarries and spoil heaps. A key element within the landscape is the variety of deglacial landforms, including in the west of the LCA the Murrins deglacial complex. Because it is generally visually intact, the impact of this moraine-outwash assemblage on the landscape is very marked, further landscape contrasts are provided by the juxtapostion of sand and gravel and bedrock and differences in ridge orientation and topography type. Moraines and feeder eskers contrast with intervening alluvial flats, meltwater channels and kettleholes. In the south of the LCA are elements of the Pomeroy complex that is classed as aesthetically poor due to the large-scale commercial sand and gravel extraction operations, visible from main roads throughout the area. This is despite the topographic diversity added to the area by deep, wide, steep-sided meltwater channels, prominent valley-side ridges and remnants of flat-topped, dissected valley-fills.
Pre-Quaternary (Solid) GeologyThe stratigraphy of this area is made up of the mapped formations in the table, the youngest of which usually overlie the oldest. The older formations can be upside down (tectonically inverted).
Stratigraphic Table (youngest rocks at the top of the table)| Tertiary - dolerite dykes and sills, about 60 million years old |
| Carboniferous - Omagh, Desertmartin, Derryloran, about 350 million years old |
| Devonian - Shanmaghery, Shanmullagh, about 400 million years old |
| Silurian - Little River Group, about 430 million years old |
| Late Caledonian - Pomeroy, Craigbardhessiagh, Carrickmore, Slieve Gallion granites, about 400 million years old |
| Early Caledonian - Tyrone Plutonic Complex |
| Ordovician - Tyrone Volcanic Group - Copney Pillow Lavas, rhyolites, about 450 million years old |
| Moinian - Corvanaghan - about 1000 million years old |
Comprises a large number of rock types of many ages in complex faulted, unconformable and intrusive relationship.
Caledonian, Variscan and post-Variscan aged faults of many orientations cross the area.
Quaternary (Drift) GeologyNorthern Ireland has experienced repeated glaciations during the Pleistocene period that produced vast amounts of debris to form the glacigenic deposits that cover >90% of the landscape. Their present morphology was shaped principally during the last glacial cycle (the Midlandian), with subsequent modification throughout the post-glacial Holocene period. The Late Midlandian, the last main phases of ice sheet flow, occurred between 23 and 13ka B.P. from dispersion centres in the Lough Neagh Basin, the Omagh Basin and Lower Lough Erne/Donegal. The clearest imprint of these ice flows are flow transverse rogen moraines and flow parallel drumlin swarms which developed across thick covers of till, mostly below 150m O.D. during a period that referred to as the Drumlin Readvance. At the very end of the Midlandian, Scottish ice moved southwards and overrode parts of the north coast. Evidence for deglaciation of the landscape is found in features formed between the glacial maximum to the onset of the present warm stage from 17 and 13ka B.P. - a period of gradual climatic improvement. Most commonly these are of glaciofluvial and glaciolacustrine origin and include: eskers, outwash mounds and spreads, proglacial lacustrine deposits, kame terraces, kettle holes and meltwater channels (McCarron et al. 2002). During the Holocene, marine, fluvial, aeolian and mass movement processes, combined with human activities and climate and sea-level fluctuations, have modified the appearance of the landscape. The landforms and associated deposits derived from all of these processes are essentially fossil. Once damaged or destroyed they cannot be replaced since the processes or process combinations that created them no longer exist. They therefore represent a finite scientific and economic resource and are a notable determinant of landscape character.
This area represents a complex boundary between Lough Neagh centred ice that approached the area from the southeast and Tyrone ice coming from the southwest. This interaction reveals itself in the local complexity of the landscape and its associated drainage. This complexity derives largely from an often seemingly chaotic arrangement of deglacial deposits formed by the wastage of the ice sheets and retreat of their margins towards their source areas. Within the LCA there are significant elements of three major deglacial complexes that are important scientifically and for their sand and gravel resources. In the west, the Murrins Complex largely reflects the retreat of ice southwestwards into the Omagh Basin, while in the east of the LCA, the Ballinderry River complex can be used to understand the westwards retreat of Lough Neagh ice. In the south of the LCA, the Pomeroy complex straddles the former interface between the two ice masses and shows evidence of retreat in both directions. These complexes are summarised below.
The Murrins Complex occupies an area in the northwest of the LCA. The Murrins complex as a whole is located in the lowland area between Carrickmore to the southeast and the upland massif of Mullaghcarn and adjacent hills to the northwest. The northern part of the complex terminates at the foothills of the Sperrin Mountains near Greencastle.. Associated esker ridges up to 8 km long occur to the south at Beragh, Coolesker, Seefin and Cloghfin. Sediments are mainly superimposed upon bedrock to the west and north, and glacial till to the east and south. The complex is characterised by proglacial outwash, frontal moraines, small retreat moraines, local, high-level deltas and discontinuous feeder eskers and local kettling and meltwater erosion. The complex also lies to the north and west in LCAs 25 and 26, with outliers to the southwest in LCAs 22 and 23.
The Ballinderry River Valley Complex occupies 25.5km2 in the centre and northeast of the LCA and is part of an area of predominantly lowland, extensively quarried glaciolacustrine sand and gravel to the southeast of the main Sperrin mountains range. The thickest deposits of stratified drift occur along the flanks of the Ballinderry river valley and on the southern highland margin of this tectonic bedrock depression. The complex is scientifically important because it demonstrates the localised southward and eastward retreat of ice and more general regional deglaciation patterns. Intact, intricate, topographic associations have been preserved including excellent examples of subglacial sediment supply and proglacial sedimentation at Lough Doo and Cam Lough. Deglacial landforms including esker complexes, Gilbert-type deltas, ice-contact slopes, outwash terraces, glaciotectonically influenced cross-valley ridges are preserved and the complex provides examples of the effects on ice-mass decay patterns of bedrock topography. The area as a whole has little aesthetic value because of extensively quarrying. There is a limited extension of 2.5km2 into LCA 25.
The Pomeroy Deglacial Complex in the south centre of the LCA is a 118 km2 area in the Fintona hills and contains units of glaciolacustrine and glaciofluvial sediments in the valleys and along the hillsides of glacially moulded bedrock highs. The area occurs along the watershed between the major depressions of the Omagh basin and Lough Neagh lowlands. The deposits and landforms record regional scale deglaciation patterns and provide evidence for the formation of localised and regional-scale waterbodies along the deglaciated southern margins of the Sperrin mountains. This deglacial phase occurred during the eastward and westward retreat of ice margins generally towards the depressions of the Lough Neagh and Omagh Basins. The complex also extends southwards into LCA 44.
Key Elements ASSIs096 LIME HILL FARM
The type locality for the zonal graptolite Monograptus sedgwickii. the site has yielded the world's oldest known Nowakiid, Nowakia brevis, for which this is also the type locality. It is one of only two localities in Northern Ireland exhibiting a shelly fauna in a Silurian graptolitic setting.
098 BARDAHESSIAGH
A highly fossiliferous sequence of Ordovician sediments. The type locality for over 50 species while many additional new species collected in 1992 still await definitive descriptions. One of the most diverse fossil faunas of Caradoc age known and of great palaeogeographical importance.
Deglacial ComplexesCAM LOUGH/SULTAN delta
This area of the Ballinderry sand and gravel landscape occupies the north-centre of LCA 43 and overlaps with LCA 25 to the north. The Cam Lough area is of importance in understanding the recent glacial history of Northern Ireland and contains excellent examples of a range of deglacial landforms including eskers, flat-topped deltas, ice-contact slopes and kettle holes. The relationship between the esker and delta series is clearly demonstrated while the ice-contact slope is pristine. The Cam Lough and Sultan complex is among the largest remaining, intact, sand and gravel units in Northern Ireland. The basinal lowland containing Cam Lough is enclosed to the west by the steep slope of a sharp-crested, hummocky cross-valley ridge that extends from the foothills of Cregganconroe to Sultan.
POMEROY DEGLACIAL COMPLEX
The complex is rated as having a good scientific importance because it provides a records of regional ice pressure from the Omagh basin area during the last glacial cycle and of a proglacially ponded water body at 245 m O.D. during the deglaciation of the area, It also demonstrates ice-marginal retreat westwards into the Omagh basin and eastwards into the Lough Neagh lowlands towards the end of the last glacial cycle. Deglacial landform associations include feeder channels and a proglacial fan, meltwater channel incision events and infills, and an excellent example of a major morainic tract at Pomeroy.
The Murrins complex
The Murrins complex records a sequence of sedimentary events associated with southwestern ice retreat from the southern Sperrin Mountains into the central part of the Omagh Basin and can be classified as being of unique importance on a Northern Ireland scale.
LOUGH FINGREAN MORAINES
The area forms an important element in the Murrins Complex in this LCA. It is characterised by major northeast to southwest oriented moraine ridges with intervening flatter outwash spreads. Ridges are associated with adjacent enclosed, water-filled depressions, such as those occupied by Lough Fingrean and Lough Carn. Ridges to the west of Lough Macrory are eskers. Landscape contrasts are provided by the juxtaposition of sand and gravel and bedrock, and by differences in ridge orientation and morphology. Kettleholes and generally intact peatland support a wide variety of habitat types.
Knockaleery Ridge
This is a large-scale linear sharp-crested cross-valley ridge which rises up to 188 m O.D. and two kilometers long is located to the south of the present course of the Ballinderry river. The ridge forms a visually prominent feature in the lower reaches of the valley, rising over 40 m above the valley floor and marks the eastern margin of the Ballinderry's large scale glaciofluvial landforms. Several large commercial pits exist in the ridge core and flanks.
Other sites/units identified in the Earth Science Conservation ReviewOrdovician
Desertcreat Group
Fossiliferous sandstones, limestones and mudstones in a small area on the southern edge of LCA43. Exposed at Bardhessiagh ASSI (098): fossils are abundant.
Tyrone Volcanic Group
The lavas are part of an ophiolitic succession - fragments of oceanic crust that have been pushed up from the ocean into a continental sequence of rocks. They comprise lava flows and pillow lavas metamorphosed during their emplacement in the Caledonian Orogeny. These lavas are generally degraded and not used in construction. Rhyolites occur in the upper parts of the group. Comprises the southwestern third of the LCA. The Laght Hill Tonalite (with rhyolite) occurs at Cashel Rock (ESCR Site 434). Copney Hill (ESCR Site 429) has exposures of typical Tyrone Volcanic Group.
Silurian
Little River Group
Mudstones and siltstones with graptolite fossils: the best exposure is at Lime Hill Farm ASSI (096) where graptolites are recorded. Forms two small protuberances on the southwestern edge of LCA42.
Early Caledonian
Tyrone Plutonic Complex
Olivene gabbros that intrude early dolerites: the dominant rock type of LCA43, making up around 50% of the total area. The contact of the plutonic complex and Tyrone Volcanic Group (with the granitoids listed below) occurs around Craigbardhessiagh ( ESCR Site 436). Other exposures occur at Scalp Hill (ESCR Site 426)
Late Caledonian
Pomeroy, Craigbardhessiagh, Carrickmore, Slieve Gallion granites
Biotite granites with abundant rafts and inclusions of earlier basic plutonic rocks. Four discrete areas along the southeastern side of LCA43. Outcrops of the Pomeroy Granite can be seen at the Craiganwork, ESCR Site 437). Associated quartz - porphyries occur at Loughmacrory (ESCR Site 439).
AONBThe northern margin of the LCA lies within the Sperrin AONB (1968). This designation is indicative of the scenic quality of the landscape.