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 Lowlands. This region owes its large-scale morphology to the early Tertiary subsidence of the Lough Neagh basin into the magma chamber from which the basalts that underlie much of the landscape originated. This has produced a largely centripetal drainage system from the rim of the basin into Lough Neagh that ultimately drains northwards via the Lower Bann. To the south of the Lough Neagh basin, the lowlands extend southwestwards along a Caledonian structural trend into the Monaghan-Clones depression. In the east of the region the lowlands extend northeastwards along the fault-guided Lagan Valley. There are no strong topographical barriers in the region and boundaries between LCAs tend to be subtle. The low gradients of the rivers, especially on the clay lowlands immediately around Lough Neagh, create inherent drainage problems and frequently it is only the slopes of the many drumlins that provide permanently dry sites. The Lough Neagh Basin was a major ice accumulation centre during the Late Midlandian and much of the lowland areas to the north and south of the Lough are dominated by extensive drumlin swarms.
The Magherafelt Farmland is a relatively elevated area adjacent to the West Lough Neagh Shores. The drumlin landform is generally not as well defined as in the surrounding lowlands, but individual small drumlins and broken ridges are important landscape features which are often up-standing from the farmland plateau. Killowen Hill, to the south of Magherafelt is a prominent example. The summits of Mullaghboy Hill, to the west of Magherafelt and Spring Hill, overlooking Moneymore are the highest points of a broken ridge line which provides long views over the deep river valley to the west. The valley landscapes contrast with the relatively windswept, open farmland. On higher land, stands of mature trees often draw attention to individual drumlins and any sharp breaks of slope. There are long views to Slieve Gallion, to the west. A key element in the west of the LCA is part of the Moneymore deglacial complex that consists of discontinuous sand and gravel mounds and spreads in a north/south oriented belt between Moneymore, Coalisland and Dungannon. The landforms are dissected and consist predominately of ice-marginal and extra-marginal glaciolacustrine sequences superimposed upon the western Lough Neagh drumlin field.
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 faulted and folded.
Stratigraphic Table (youngest rocks at the top of the table)| Tertiary intrusive units - between 50 and 60 million years old |
| Tertiary Lower Basalt Formation - about 55 million years old |
| Cretaceous Hibernian Greensand & Ulster White Limestone - about 100 million years old |
| Triassic Mercia Mudstone Group - between 220 and 210 million years old |
| Carboniferous - various - about 350 million years old |
| Devonian Old Red Sandstone - about 400 million years old |
| Caledonian Granite - about 420 - 400 million years old |
This LCA extends across the basalt escarpment to the west of Lough Neagh. Here, Cretaceous greensands and limestones or Tertiary basalts rest unconformably on a range of older Mesozoic and Palaeozoic rock units. The LCA comprises 75% Tertiary basalts, the remainder being the older, underlying units. The geological succession appears complex but is in fact quite simple, being mostly basalts.
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 for this LCA shows that most of it is dominated by till deposits resulting from the drumlin readvance. Although there are significant drift-free areas in the centre of the LCA associated with the slightly higher ground to the south of Magherafelt. The landscape is shown in Edwards (1980) to be dominated by large numbers of SE-NW orientated drumlins that form part of the Western Lough Neagh Drumlin Field. 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.
The exception to the drumlin dominated terrain occurs in the west of the LCA, which contains significant elements of a major deglacial complex that is important scientifically and for its sand and gravel resources. The Moneymore Glaciofluvial Complex covers 3.1km2 of this LCA along its western margin with LCA 41 and extends south into LCAs 42 and 45. The Moneymore complex consists of discontinuous sand and gravel mounds and spreads in a north/south oriented belt in the Lough Neagh lowlands to the east of the Sperrin highlands between Moneymore, Coalisland and Dungannon, Co. Tyrone. The landforms are dissected and consist predominately of ice-marginal and extra-marginal glaciolacustrine sequences superimposed upon the western Lough Neagh drumlin field. The stratified deposits formed in association with localised and variable palaeolake levels during the final deglacial stages of the region. Sediment supply was largely from a small, lowland residual ice-mass within the Lough Neagh basin and meltwater draining the eastern margin of the Sperrin highlands.
Key Elements Deglacial ComplexesMONEYMORE glaciolacustrine COMPLEX
The Moneymore complex has good scientific value, and records the final ice-margins in the Lough Neagh lowlands during the deglacial period following eastward wastage of the ice from the Sperrin mountains and Fintona hills into the lowlands. It also demonstrates the control shown by local (predominately drumlin) topography on waterbody ponding during the late stages of ice decay and is one of the few lowland locations recording the presence of fine-grained, glaciolacustrine sediments.