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 Western River Basins. This region consists essentially of the connected river systems that drain the Carboniferous and Old Red Sandstone plateau of County Tyrone, as well as the foothills of the Sperrin Mountains to the east and Donegal to the west. The region extends from the Omagh Basin in the south, northwards along the lower Foyle valley. The Omagh Basin has particular significance as an ice centre during the Late Midlandian and is now largely covered by a complex mixture of glaciofluvial sands and gravels and drumlins overlying Rogen moraines. When the headwaters of these river systems rise together they have in the past been responsible for serious flooding at the bottleneck of Strabane. Although this has been mitigated by extensive drainage control works in and around the town.
The Fairy Water flows eastwards from the foot of Bolaght Mountain in West Tyrone to meet the Strule near Omagh. The Fairy Water Valley includes the broad, marshy valley of the Fairy Water and the undulating branching valley of the Drumquin River to the south. The village of Drumquin is on the banks of the Drumquin River is an exceptionally scenic valley landscape setting. The Fairy Water Valley is an expanse of peaty marsh, which extends right across the valley floor. At a small-scale, the landform is hummocky and irregular. Fragmented remnants of the geometric patchwork of small pastures remain on the outer margins of the valley floor but the field pattern breaks down in poorly drained areas to form a random, irregular mosaic of peaty marsh and woodland. To the south, the Drumquin Valley has a flat valley floor and undulating valley slopes, with a small-scale, irregular patchwork of pastures. It is on the margins of the drumlin lowlands and the rounded landforms reflect this influence. The landscape can therefore be summarised as one of a patchy mosaic of scrub, bog, peaty marsh and carr woodland on wide floodplain.
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, about 60 million years old |
| Carboniferous - about 350 million years old |
| Mullaghmore Sandstone (east only) |
| Bundoran Shale |
| Ballyshannon Limestone (including Waulsortian Limestone) |
| Claragh Sandstone |
| Omagh Sandstone (Group) |
| Neoproterozoic (Dalradian) Mullaghcairn Schists & Psammites, Claudy, Dungiven formations - about 600 million years old |
This LCA is dominated by Carboniferous rocks of the Kesh - Omagh succession in faulted contact with the older Neoproterozoic metamorphosed rocks. Tertiary dolerite dykes extend through the area. Overall, the area can be split into three broad areas of geology: a northern tip of Dalradian (mostly Dungiven Limestone); a central are of Claragh Sandstone (about 65% of the total LCA) and a complex, faulted southwestern area of Mullaghmore Sandstone, Bundoran Shale, Ballyshannon Limestone, faulted against Omagh Sandstone and again against older rocks.
The Carboniferous Ballyshannon Limestone (dark, fossiliferous limestones) includes the Drumowen Sandstone Member, exposed at Carrickaness Bridge (ESCR Site 215). The Bundoran Shale comprises interbedded grey, black and brown shales with minor siltstones and limestones. Highly fossiliferous (crinoids, brachiopods, bryozoa, corals). Restricted to five fault-bounded segments in the southwest of LCA21. Exposed in Moffatt's Quarry (ESCR Site 218).
The rock succession was strongly deformed in the Variscan Orogeny: a NE-SW fault in the south of the area parallels the Omagh Thrust (south of this LCA).
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.
The drift geology map shows that the western, upland area of the LCA is dominated by drift-free bedrock that would have been overridden by Late Midlandian ice that moved northwards across the area from its centre in the Omagh Basin. This same ice was responsible for the extensive area of till in the east and southeast of the LCA that is characterised by drumlin development. Within Northern Ireland, drumlins take a variety of forms; some are rounded in plan, although the majority are elongated in the direction of ice flow. Some have sharp crests, whereas others are more whaleback in profile. Although most drumlins are composed of glacial till or tills, a small number are 'drumlinoid features' are rock-cored and some are composed of sand and gravel. Where drumlins are rock cored there may have been significant frost shattering prior to their shaping by ice flow. It is possible therefore to see tails of shattered debris within till leading away from the feature in the direction of flow (Davies and Stephens 1978). It is generally accepted that the drumlins of Northern Ireland were formed by deposition beneath fast flowing ice. In the majority of cases this has resulted in a thick layer of Upper (younger) Till overlying a core of Lower (older) Till. This pattern has been observed across Northern Ireland, apart from a limited area in the north of County Down. The precise temporal relationship between the two tills has not been definitively resolved, but Davies and Stephens (1978) refer to an organic layer between the tills in County Fermanagh that has been dated at 30 500 ± 1170/1030 years B.P. and shelly material between the tills on the Ards Peninsula dated at 24 050 ± 650 years B.P.. However, these deposits only indicate that the Lower Till is older than the dates obtained and cannot be used determine whether it is Midlandian or pre-Midlandian in age.
The drift geology map also highlights the very extensive alluvial deposits associated with both the Fairy Water and Drumquin rivers.
Key Elements ASSI1008 FAIRY WATER BOGS
Composite site; three examples of intact lowland raised bogs with well developed dome structure and hummock-hollow complexes. High Sphagnum cover.
Deglacial ComplexesFOYLE VALLEY COMPLEX
There is a small area of hummocky moraine and outwash (0.2km2) belonging to the Foyle Valley deglacial complex in the southeast of the LCA.
Other sites/units identified in the Earth Science Conservation Review215 Carrickaness Bridge
Carboniferous. Exposure of stratotype for Drumowen sandstone member of Ballyshannon Limestone Formation.
219 Moffatt's Quarry
Carboniferous. Exposure of Bundoran Shale Formation. Also the base and contact with underlying Ederny Limestone Member of Ballyshannon Formation is exposed. Fossiliferous layers.
353 Garvaghullion Bog
Peat stratigraphy. Detailed pollen and tephra record. Prehistoric wooden trackway.