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 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 Six Mile Water flows within a broad, gently undulating valley which acts as a corridor for the dense infrastructure linking the towns of Antrim and Ballyclare. The west of the area borders the Lough Neagh lowlands to the southwest and the Antrim plateau that rises to the north and south. A shorter tributary, the Three Mile Water, extends southeast from this principal valley to Newtownabbey, where the soils are relatively poorly drained. Large scale built development and infrastructure is prominent in some areas, particularly on the fringes of Newtownabbey and Antrim. Carnmoney Hill is a prominent outlier from the Belfast Basalt Escarpment, which forms a landmark for Newtownabbey. The hill has a rugged, natural landscape, with a dramatic escarpment to the south. Geomorphologically, an important element in the landscape is a series of glaciofluvial deposits that occur along the northern banks of the Six Mile Water. This is in turn aligned along a bedrock depression in Tertiary Lower Basalts controlled by the Six Mile Water fault. Within the valley floor of the Six Mile Water is a significant glaciofluvial complex. This has little aesthetic merit because the deposits are largely visually unobtrusive and occur as a discontinuous belt through a well populated lowland area of improved farmland. Localised areas of intact glaciofluvial topography composed of ridges, hummocks and hollows do, however, add some topographic diversity along main route ways through the valley.
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 - various intrusives (mostly dykes and dolerite plug), around 55 million years old |
| Tertiary - Upper Basalt Formation, about 55 million years old |
| Tertiary - Interbasaltic Formation, about 55 million years old |
| Tertiary - Lower Basalt Formation, about 55 million years old |
| Cretaceous - Hibernian Greensand & Ulster White Limestone, around 100 million years old |
| Jurassic - Waterloo Mudstone, about 200 million years old |
| Triassic - Penarth Group about 205 million years old |
| Triassic - Mercia Mudstone Group, between 230 and 205 million years old |
| Triassic - Sherwood Sandstone Group, between 245 and 230 million years old |
The geology comprises a mix of Mesozoic sedimentary and Tertiary igneous rocks in faulted and unconformable contact. Tertiary Lower Basalt Formation makes up 65% of the LCA with the remainder being the other formations in varying proportions.
The folded Triassic sandstones comprise red, purple and brown cross-stratified sandstones, siltstones with minor clay beds and partings that crop out at Whiteabbey and Macedon Point in the southeast of the LCA. They form an aquifer in this area. The top of the Sherwood and base of the Mercia can be seen in Glas-Na-Bradan stream (ESCR Site 448).
Below the Cretaceous - Tertiary escarpment, the low ground is underlain by soft sedimentary rocks of the Triassic Mercia Mudstone Group. The main outcrop is above the Sherwood Sandstone anticlines of the coastal area . The beds form an aquiclude, soft and contain anhydrite. They have been quarried for brick clays here and elsewhere in last 200 years.
Fossiliferous limestones and black shales make up the Penarth Group. It occurs as a narrow outcrop strip in the sub-Cretaceous escarpment of Mossley and Carnmoney.
The Jurassic Waterloo Mudstone Formation, crops out in a fault-bounded strip in the south of LCA114 below the basalt escarpment. 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 a linear exposure below the Tertiary basalts of LCA113. Fossiliferous sands and 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 Lower Basalt Formation occurs in an extensive outcrop of the plateau of the LCA. They are extensively quarried for construction materials, especially roadstone. Ash-falls within the Lower Basalts are recorded and one such unit occurs in an arcuate outcrop between Dunadry and Templepatrick in the south of the LCA. Exposed in Craig Hill Quarry (ESCR Site 447).
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). In the central part of LCA114 these two formations are separated by red, palaeoweathered beds and ashfalls of the Interbasaltic Formation. Within the Interbasaltic Formation, lava flows are well-known from Tardree and within this LCA at Templepatrick where the rhyolites are part of an igneous centre that brought Cretaceous Ulster White Limestone to surface. The Interbasaltic Formation is exposed at Ballypalady Railway Cutting ( ESCR Site 298) where fossil plants occur.
NE-SW oriented faults dominate the outcrops of Tertiary rocks and juxtapose all the above formations. The major NE-SW Sixmilewater Fault crosses the area, juxtaposing all Tertiary formations and running just north of the Templepatrick igneous centre. A broad anticline (NW-SE trending axis) brings Sherwood Sandstone to surface at Whiteabbey.
Dykes occur throughout the area: the most obvious are those seen cutting soft Mercia Mudstone group or in white limestone; dykes also cut the Lower Basalts. These trend NW-SE but other dyke trends occur. An elliptical dolerite plug that was once ths site of a volcano occurs in the southeast side of Carnmoney Hill. This, the Carnmoney Plug, can be seen in the quarry at Carnmoney Hill (ESCR Site 446).
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 it to be predominantly underlain by 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. The most prominent exception to this complete drift cover is the bedrock mass of Carmoney Hill in the east of the LCA. This is in effect an outlier of the basalt-capped Antrim Plateau and has many of its geomorphological characteristics. This includes a large area of landslip below its eastern escarpment that is similar to those found above Belfast in LCA 112. 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 ice free and surrounded by encircling ice. Because of the oversteepening of the basalt escarpment by ice within the Lagan Valley, and the presence beneath the basalt and chalk of an impermeable, but weak layer of Lias and Rhaetic clays, the escarpment was inherently unstable following the removal of ice support from the Lagan Valley. Instability would have been further enhanced by the greater availability of groundwater as climatic conditions ameliorated. The collapse of large sections of the escarpment therefore represents a post-glacial adjustment in the landscape. This continues into the present-day, as the dropping down of large masses of basalt and chalk had the effect of bulging out the underlying beds, especially the Triassic marl.
However, the Quaternary features that are of possibly greatest geomorphological and geological significance are located within areas of deglacial sand and gravel along the valley of the Six Mile Water. These comprise most of the Six Mile Water Glaciofluvial Complex (5.4km2) that occurs in a discontinuous, low-relief linear belt for approximately 18 km from Antrim to Ballyclare. It probably records both subglacial and subareal channelised glaciofluvial sedimentation during the deglacial period as an ice lobe retreated westwards along the depression towards the Lough Neagh lowlands. As such, they assist our understanding the complexity of deglacial processes during the recent glacial history of Northern Ireland. The glaciofluvial topography along the Six Mile Water depression probably represents part of a subglacial palaeohydraulic system which conducted meltwater generally northwestwards from the Lough Neagh lowlands during the last deglacial event. The palaeoflow is associated with a high piezometric surface that forced meltwater flow uphill against the local topographic gradient.
Superimposed on both till and glaciofluvial deposits are ribbons of alluvial material associated with the floodplains of the present-day drainage system.
Key Elements ASSI104 OUTER BELFAST LOUGH
Outer Belfast Lough is a structurally defined feature, possibly marking the continuation of the major Southern Uplands Fault from Scotland to Ireland. The site is important for the Ordovician seris of spilitic lavas, black shales and greywackes. The Carboniferous series of the Holywood group are also of significance and the Permian rocks are the best exposed series of rocks of this age in Ireland. The habitat range includes open mud flats, boulder and rock shore, extensive mussel beds and a narrow shoreline strip of semi-natural vegetation including small, isolated pockets of beach-head saltmarsh.
Deglacial ComplexesTHE SIX MILE WATER GLACIOFLUVIAL COMPLEX
The Six Mile Water complex has limited scientific importance, but it does provide the only evidence in the region of ice pressure from the direction of the Lough Neagh lowlands during the last glacial period and indicates that the Lough Neagh basin formed a lowland centre of ice decay. As such, it demonstrates the influence of regional topography upon the drainage pattern of the ice sheet.
Sites/units identified in the Earth Science Conservation Review298 Ballypalady
Palaeontological. Interbasaltic Plant Beds. Important for palaeobotanical and palaeoenvironmental science. Significant fossils, especially plant material.
446 Carnmoney Plug
Exposure of large Palaeogene volcanic plug, that acted as local lava feeder for Lower basalt Formation.
447 Craig Hill Quarry
Good exposures of Lower Basalt Formation with a number of unusual features preserved within the basalt.
448 Glas-Na-Bradan
Exposure of transition between Sherwood Sandstone Group and Mercia Mudstone Group. Upto 6 basaltic dykes intrude into these Triassic marls and mudstones.