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 Moyola Floodplain is dominated by the low-lying floodplain landscape of the Moyola River to the south of Maghera. The landform is almost flat beside the river, and the very shallow slopes are generally the flattened remnants of drumlins. There are numerous meandering rivers and branching tributary streams. The land rises to the east, where drumlins predominate and the landscape is more settled, with clustered villages and belts of woodland. Aesthetically, the Moyola glaciofluvial complex on the western and southern border of the LCA is important because of the topographic diversity provided by visually prominent ridges, interspersed with meltwater gashes and broad alluvial spreads on the flanks of the ridges.
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.
Stratigraphic Table (youngest rocks at the top of the table)| Tertiary - Lower Basalt Formation, about 55 million years old |
| Triassic - Sherwood Sandstone Group, about 240 million years old |
| Carboniferous - Iniscairn, Altagoan, Desertmartin - about 350 million years old |
Comprises three ages of rock strata: Carboniferous (Upper Palaeozoic) clastic and carbonate sediments, just over 50% of the south-east of the LCA; Triassic (Mesozoic) sandstones in an east - west strip and Tertiary basalts, just under 50% of the north-east of the 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 for this LCA shows that to the north it is underlain by an area of till that is characterised in Edwards (1980) as a landscape of subdued drumlins. These are orientated approximately SE-NW and are a product of fast flowing ice moving northwestwards out of the Lough Neagh Basin. The south and west of the LCA contain significant glaciofluvial sands and gravels that were deposited during the deglaciation of the region as the Lough Neagh ice wasted. In the west, these comprise a small area (0.5 km2) of the The Moyola Valley complez. This consists largely of subglacial, glaciolacustrine, morainic and alluvial sediments on low ground in the Moyola river valley. Sand and gravel landforms consist of pristine flat-topped ridges, dissected flat-topped ridges, large- and small-scale linear cross-valley ridges and isolated meltwater eroded hummocks. These are surrounded by flat, extensive alluvial spreads. Most of the Complex is in LCA 40.
The drift map also highlights the extensive alluvial deposits associated with the present-day Moyola River.
Key Elements Deglacial ComplexesMOYOLA VALLEY DEGLACIAL COMPLEX
The Moyola Valley complex is scientifically important through providing a record of complex proglacial landform deposition during during the last deglacial cycle. The preserved morphology records proglacial waterbodies and landform patterns and palaeoflows record the general eastward retreat of the ice-lobe that occupied the valley during the last deglacial period. It also provides evidence in support of models of a generally south and eastward retreat of ice from the Bann Valley towards the Lough Neagh lowlands and toward the eastern flanks of the Sperrin Mountains.
BELMOUNT HILL SAND AND GRAVEL SPREAD (MOYOLA VALLEY DEGLACIAL COMPLEX)
An extensive, dissected spread of sand and gravel inferred to result from the deposition of sediments in an ice-marginal lake located at the southeast entrance of the Moyola River valley. Landforms record deglacial processes during ice withdrawal towards the Lough Neagh Basin. The adjacent Black Hill area is an excellent example of the landforms produced at a time when glacier ice was increasingly confined to low altitude valleys and basins. Most of this outwash occurs in LCA 40.
Other sites/units identified in the Earth Science Conservation Review258 Drumbally Hill
Exposures of Desertmartin Limestone Formation. Some crinoid and brachiopod fossils.