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.
Garry Bog is a flat area of farmland, carr, raised bog and coniferous forestry which includes the large straight edged Garry Wood. It extends west from the Bush River north of Ballymoney, and forms the floodplain to a number of its tributaries. A key element in the landscape is a section along the south and southeastern border of the LCA is a massive ridge that dominates the landscape to the northeast of Ballymoney and is known as the Armoy Moraine. The moraine ridge system marks the southern extent of an advance of Scottish ice, which pushed up sediments that had previously been deposited by a northwards moving ice mass centred on Lough Neagh. Garry Bog has formed in the poorly drained lowland between the morainic 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.
Tertiary (Antrim Lava Group) stratigraphic succession (between 50 and 60 million years old)
Stratigraphic Table (youngest rocks at the top of the table)| Tertiary Lough Neagh Group mudstones & lignites - about 20 million years old |
| Tertiary Upper Basalt Formation - about 50 million years old |
Part of the Ballymoney Basin comprising 55% Lough Neagh Group and 45% Upper Basalt Formation.
Upper Basalt Formation
Comprise a crudely-bedded succession of lava flows, columnar jointed lava flows, ash-falls and red-weathered horizons (or boles). They are extensively quarried for construction materials, especially roadstone. Occurs in a 1 - 3km-wide arcuate outcrop around the northwest edge of LCA55.
Lough Neagh Group
The Tertiary Lough Neagh Group comprises soft mudstones and lignites (soft coal). The mudstones have been mined for brick manufacture and the lignites form an economic coal power resource in this area. Underlies the southeast of LCA55.
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 southern boundary of this LCA overlaps a limited area (0.4 km2) of a deglacial complex that is important scientifically and for its sand and gravel resources.
The Armoy Moraine comprises a dominant feature of the local landscape that marks the southern extent of an advance of Scottish ice, which pushed sediments that had previously been deposited by an ice mass centred on Lough Neagh. The Armoy moraine is up to 4km wide, extends about 20km, northeastwards from Ballymoney into the Tow River valley and consists of large continuous ridges. Sediments within the moraine are typical of lake deposits, probably laid down by meltwater emanating from an ice body centred on Lough Neagh. Exposures have shown that these deposits were then pushed from the northwest by an ice body of Scottish provenance. Exposures have also shown that the top of the feature has been planed off. Together with the distribution of streamlined landforms, this indicates that retreat of Scottish ice was followed by a northward advance of Lough Neagh-based ice. Most of this moraine is found in LCAs 54 and 56.
The drift geology map for this LCA shows the confining distribution of the Armoy Moraine, but emphasises that this LCA essentially comprises a singular expanse of lowland bog formed over Late Midlandian till.
Key Elements ASSIs004 GARRY BOG
Undamaged lowland raised bog with partially intact lagg and good pool system. High Sphagnum cover. Nationally rare Sphagnum pulcrum occurs.
127 GARRY BOG PART 2
Lowland raised bog adjacent to Garry Bog ASSI. The intact surface displays a small pool complex with moderate hummock and hollow development supporting a number of rare species.The Garry Bog system is internationally significant for peat stratigraphy which displays a classic sucession from clay and lake muds , through reed swamp and wood peats to raised bog peats . Recently volcanic glass shards (tephra), have been identified in the peat column , permitting more reliable correlation of the peat stratigraphy .
Deglacial ComplexesARMOY MORAINE
The moraine is of great importance in reconstructing the chronology of ice front oscillations towards the end of the deglacial cycle and understanding the complexity of deglacial processes. Limited aggregate extraction perhaps reflects the fact that many of the sediments within the moraine are of fine-grained sands and silts of lakebed origin. The pristine condition of the landform suggests that at least this part of the moraine should be protected with regard to controls on aggregate extraction.