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 in the south east of the region described as the Antrim Plateau and Glens. This upland area is dominated by a series of structural plateaux that dip gently in towards the Lough Neagh Basin. Detailed topography is largely controlled by a succession of Tertiary basalt lava flows that define successive, large-scale steps within the landscape. The plateaux are separated from each other and their frequently dramatic margins are fretted by often fault-guided, steep-sided glens. Recession of the plateaux margins has exposed underlying Mesozoic strata and, in some areas, the Palaeozoic basement. The plateaux margins are typically characterised slope failures that range from large rotational landslides to individual blockfalls.
The landscape of the Carrickfergus Upland Pastures reaches an elevation of 200-250m. The area is underlain by basalt, but the shallow soils, rocky exposures and wet climate create less productive farmland than elsewhere. Shallow ridges extend from the basalt escarpment to the south to create an undulating plateau. Landuse is predominantly pastoral with small, regular fields enclosed by gappy hedges, as well as by earth banks and stone walls. A number of loughs are also found within this character area, including the dammed South and North Woodburn reservoirs and Lough Mourne. The visual influence of these waters on the landscape is limited owing to the forest screen, but they are significant local features. The area can therefore be summarised as an undulating landscape of low ridges and shallow valleys.
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 - Upper Basalt Formation, about 50 - 55 million years old |
| Tertiary - Interbasaltic Formation, about 50 - 55 million years old |
| Tertiary - Lower Basalt Formation, about 50 - 55 million years old |
| Cretaceous - Hibernian Greensand & Ulster White Limestone, around 100 million years old |
| Jurassic - Waterloo Mudstone, about 205 million years old |
| Triassic - Mercia Mudstone Group, between 220 and 210 million years old |
The geology comprises a mix of Mesozoic sedimentary and Tertiary igneous rocks in faulted and unconformable contact.
Below the Cretaceous - Tertiary escarpment and in fault-bounded strips within the Tertiary basalts, low hills and low ground are underlain by soft sedimentary rocks of the Triassic Mercia Mudstone Group. This group comprises occasionally calcareous red silstones and mudstones with subordinate grey-green siltstones, mudstones and halite. Centimetre-thick grey or red sandstones may occur. The Mercia Mudstone Group is predominantly red-brown and unfossiliferous in the lower parts of the exposed succession, becoming grey-green, sometimes fossiliferous and sometimes carbonate-cemented toward the top. The beds form an aquiclude, soft and contain anhydrite.
The Jurassic Waterloo Mudstone Formation, crops out in fault-bounded strips within the Tertiary basalts. These dark grey mudstones, grey to black shales and minor limestones are fossiliferous representatives of the Lower Jurassic or Lias.
The Cretaceous succession is found in linear, fault-bounded exposures within the Tertiary basalts of LCA98. Fossil-bearing greensands are recorded from the base of the succession. The presence of the Ulster White Limestone Group is known from isolated exposures, old limekilns and marlpits in the area. 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). These two formations are separated by red, palaeoweathered beds and columnar basalts of the Interbasaltic Formation (IBF), the stratigraphy is summarised below. The best exposure is at Beltoy (ESCR Site 80).
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 undulating landscape of this upland area is reflected in a drift cover that is interspersed with numerous ridges of drift free bedrock. In between these outcrops are expanses of Late Midlandian till associated with the large ice mass that was centred on the Lough Neagh Basin. This ice moved approximately northeastwards from an ice divide running along the crestline of the Belfast Hills. In doing so, Griffith and Wilson (1982) indicated that it left a limited number of drumlins that confirm the ice flow direction. 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 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. 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.
Davies and Stephens (1978) consider that the final stages of ice-wasting in the east of Northern Ireland probably involved wide scale stagnation, downwasting and withdrawal inland towards the Lough Neagh lowlands (p.176). This would have left upland areas such as the Antrim Plateau as ice free areas surrounded by encircling ice.
Key Elements Sites/units identified in the Earth Science Conservation Review80 Beltoy
Tertiary.