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 at the northern boundary of the region described as the Uplands and Drift Covered Lowlands of Down and Armagh. The generally subdued relief associated with the underlying basement complex of highly folded Palaeozoic strata provides the unity of this region. Relative relief is provided in the north by the Silurian hills that overlook the lower Lagan Valley, The Newtownhamilton Plateau in south Armagh, the Caledonian igneous complex of Slieve Croob and the structural depression that underlies and defines Strangford Lough. Below ca 350m, there is an almost complete mantle of drumlins forming an internationally acknowledged type example of a 'drumlin swarm'.
The Bangor Coastline forms a linear shoreline strip extending from the edge of Belfast, at the head of Belfast Lough, to Groomsport at its mouth. It is a strip of land with a gently undulating topography that supports a patchwork of pasture, mature deciduous woodland and dense urban development. Views are generally short due to the well wooded character of the coast, but the exposed coast line has an open rocky edge and patches of low growing gorse and scrub; it provides opportunities for long panoramas across the Lough. Orford (in Whalley et al. 1985) has described Belfast Lough as the fault-guided boundary between the Palaeozoic basement to the south and the Tertiary lava plateau to the north. There has been considerable man made modification of the shoreline over the last one hundred years. And most of the coastal road system and the northern edge of Belfast is on 'made ground'. Some minor sea level falls have accompanied this landfill. Sediment supply to the Lough is now very limited and in some cases, as at Carrickfergus, shoreline extensions have overstepped existing sediments and have required the construction of coastal defences. Tertiary dyke swarms orthogonal to the lough shore have acted as natural groynes and have lead to the limited development of crenellate bays.
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, about 55 million years old |
| Triassic - Sherwood Sandstone Group, around 240 million years old |
| Permian - Enler and Belfast Group, around 250 million years old |
| Carboniferous - Holywood Group, about 350 million years old |
| Lower Palaeozoic (Ordovician) - Gala Sandstone, Gilnahirk Group, Helen's Bay Formation, between 490 and 450 million years old |
The easternmost area south of Bangor encroaches upon the Lower Palaeozoic outcrop of Gala Group greywackes. To the north and extending along the southern margin of LCA103 the older Gilnahirk Group forms the lower slopes of the Craigantlet Hills. The greywackes vary from a few centimetres to a few metres in thickness with a large proportion of rock fragments and a fine-grained matrix.. Both units are commonly quarried as a source of aggregate. Minor conglomerates and volcanic ash-beds (or bentonites) and pillow lavas (e.g. at Helen's Bay) occur: these, and the enclosing black shales, make the exposure unique - ASSI104 or the Craigavad - Grey Point succession of ESCR Site 453 and ASSI 104. The southeastern area of Gala Sandstones includes the abandoned lead mine workings at Conlig. The Carboniferous "Holywood Group" succession at Cultra has a total thickness of about 280m and comprises sandstones, greenish calcareous mudstones and shales.
The Permian comprises red-brown sandstones, conglomerates, siltstones. The topmost 1-4 metres of the Belfast Group comprises the Magnesian Limestone Formation (8.5m), a dolomitic, fossiliferous limestone, quarried in Norman times for the cornerstones of Carrickfergus Castle.. This unique exposure falls in ASSI 104. Triassic sandstones comprise ~350m of red, purple and brown cross-stratified sandstones, siltstones with minor clay beds and partings.
NW-SE trending dolerite dykes occur throughout the area and are especially obvious in the northern coastal area within the Gilnahirk Group.
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 the area shows that most of it is underlain by Midlandian till. Topographically the till comprises an extensive suite of isolated drumlins, some with rock cores, which are orientated approximately north to south. The majority of drumlins across Northern Ireland comprise a thick layer of Upper (younger) Till overlying a core of Lower (older) Till. The exception to this rule occurs in North Down, where Hill(1971) observed drumlins composed only of Lower Till. These are thought to have formed in response to ice that flowed southwards from the North Channel. 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.
In the southwest of the LCA at the head of Belfast Lough an area of 'reclaimed' land is mapped, although the boundary of this must constantly change as more of the Lough is infilled. Behind this is an expanse of glaciofluvial deposits that form part of the Lagan Valley Deglacial Complex. This is a discontinuous belt of glaciofluvial and glaciolacustrine deposits that occurs for 40km along the axis of the Lagan valley from Belfast WSW to Aghalee, Co. Antrim.
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 series 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 ComplexesLAGAN VALLEY DEGLACIAL COMPLEX,
The Lagan Valley Deglacial Complex is highly important in understanding the complexity of deglacial processes. Streamlined landforms along the margins of the valley and glacially moulded bedforms indicate ice advance and episodes of fast ice flow from the west. Glaciolacustrine deposits indicate that during initial deglaciation the lower valley contained an ice-dammed lake, probably impounded by Scottish ice in outer Belfast Lough. A lobe of Irish ice located in the valley, related to ice pressure from the Lough Neagh Lowlands contained subglacial conduits now recorded by eskers that probably supplied sediment to the Malone deltaic sands that now underlie most of south Belfast. The phased retreat of the ice lobe further westward is recorded by cross-valley, ice-contact ridges. During the final deglaciation, drainage was to the west, indicating a reversal in the drainage gradient probably due to isostatic depression of the Lough Neagh Lowlands during the last glacial cycle.
Sites/units identified in the Earth Science Conservation Review453 Craigavad - Grey Point
Exposure of section through part of Upper Ordovician Gilnahirk Formation and volcanic Helen's Bay Formation.