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. 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 Dervock Farmlands, situated north of Ballymoney, comprise open, rolling intensive farmland crossed by small valleys of the tributaries of the River Bush. The area is underlain by the rocks of the Upper Basalts and has fertile brown soils. Mixed land uses are characteristic, dominated by improved pasture, potato fields and some arable use. A regular patchwork of fields is separated by neatly clipped hedgerows, fences and mature hedgerow trees, which have a windswept appearance close to the coast. Further inland there are small flat areas of raised bog, sometimes cut for peat. Geomorphologically, the south and east of the LCA is dominated the massive ridge of the Armoy Moraine to the northeast of Ballymoney. The moraine ridge 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 ridge forms the only appreciable topographical diversity in the region, bordered as it is by the monotony of streamlined ridges and the slopes of Knocklayd. The sedimentological variation within the ridges has largely preserved them from quarry scars and skyline alteration. The ridges therefore form a pristine skyline feature in a tectonic depression allowing their observation from up to 5 km away.
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 Lough Neagh Group - about 20 million years old |
| Tertiary Upper Basalt Formation - between 50 and 60 million years old |
| Tertiary Interbasaltic Formation - between 50 and 60 million years old |
| Tertiary Lower Basalt Formation - between 50 and 60 million years old |
| Cretaceous Hibernian Greensand & Ulster White Limestone - about 100 million years old |
| Triassic Sherwood Sandstone Group - about 240 million years old |
| Neoproterozoic (Dalradian) - about 550 million years old |
The geology comprises a mix of Neoproterozoic metamorphic, Mesozoic sedimentary and Tertiary igneous rocks in faulted and unconformable contact. The NE Antrim Neoproterozoic (Dalradian) comprises metamorphosed sediments and volcanic rocks, including "green beds" and marbles. The succession is equivalent to that exposed in Kintyre and is similar in being inverted (i.e. upside down), a product of tectonic events.
Triassic (Sherwood Sandstone Group) comprise red, purple and brown cross-stratified sandstones, siltstones with minor clay beds and partings. The sandstones are soft and poorly-consolidated although in adjacent LCAs cemented beds (exploited for building stones in the past) are known.
The Cretaceous succession comprises greensands and chalky limestones.
The two Tertiary-aged basalt formations comprise a crudely-bedded succession of lava flows, columnar jointed lava flows, ash-falls and red-weathered horizons (or boles).
There are three main orientations of normal faults throughout the area: NW - SE and east - west faults dominate the coastal outcrops of Mesozoic and Tertiary rocks. In the southeast of the area, the major NE-SW oriented Tow Valley Fault juxtaposes Dalradian against Tertiary basalts in the northeast and basalts against Lough Neagh Group clays of the Ballymoney Basin in the southwest.
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 LCA contains the most significant extent (26.8km2) of a major 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.
Although the drift geology map for this LCA highlights the glaciofluvial deposits associated with the Armoy Moraine, it also identifies the extensive till cover laid down by the Lough Neagh ice. This is characterised by extensive drumlin fields both north and south of the moraine. These are oriented S-N, but those in the north were overridden by ice moving in both directions. 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. It can be argued that an equally important component of any 'drumlin landscape' are the similarly numerous inter-drumlin hollows. The majority of these hollows would have held open water from local runoff at the end of the Pleistocene. Whilst some continue to exist as isolated small loughs, many have now been infilled by sediment washing off the surrounding drumlins. This has created typically flat-bottomed, marshy areas between the drumlins that are subject to seasonal inundation.
The map also highlights the extensive peat deposits that developed in the poorly drained areas between the moraine ridges, especially Garry Bog (LCA 53).
Key Elements ASIClontyfinnan
Part of the Armoy Moraine, see below
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.
AONBsParts of the north of the LCA overlap the Causeway Coast AONB (1989), whereas the eastern boundary incorporates a small part of the Antrim Coast and Glens AONB (1988). These designations are indicative of the scenic quality of the landscape.