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 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 Outer Ards Coast is a long, narrow strip of coastal land extending along the east coast of the Ards Peninsula from Groomsport to Cloghy. The landform is gently sloping, with an exposed rocky coastline which extends into the sea as small off-shore rocky islands. The intertidal foreshores provide a wide range of habitats and support a high diversity of wildlife. Orford (in Whalley et al. 1985) has described the outer coast along the Ards peninsula as a series of crenellate bays hinging on eroding drumlins or Tertiary dykes that normally open to the north. A number of sediment cells can be recognised along the coast defined by littoral drift reversals related to shifts in wave energy. Good examples of swash ridge welding under fair weather conditions can be seen in the bays. The Silurian basement crops out along the nearshore and acts as a 'reef' type barrier to wave attack. A number of sites along the outer Ards coast are recognised for their importance to earth science. Important geomorphological features include the storm ridge system and raised beach at Ballymacormick Point and a depositional site at Roddans Port that has been used to understand post-glacial sea level fluctuations.
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 |
| Lower Palaeozoic - Ordovician (predominant) - Moffat Shale and Gala Sandstone, Gilnahirk Group, 490 and 450 million years old |
Extends along the coastal strip from Bangor to Millin Bay. Predominantly Lower Palaeozoic greywackes and shales with numerous minor igneous intrusions. 99% of the LCA comprises Lower Palaeozoic (predominantly Ordovician Gala Group) greywacke sandstones and shales, the remainder being Tertiary intrusives. The structural features at Orlock, White House Port, Kearney Point, Whiskin Rocks and Millin Bay; the igneous intrusives of Ballyferris and Ballyhalbert are covered by ASSI 105.
The Gilnahirk Group is separated from the Gala - Moffat succession by the NE-SW Orlock Bridge Fault which continues onto Copeland Island. The greywackes are of sandstone grade and vary from a few centimetres to a few metres in thickness with a large proportion of rock fragments and a fine-grained matrix. The greywackes are commonly quarried as a source of aggregate; they are interbedded with thinner beds of siltstone or mudstone, commonly arranged as fining-up cycles. Minor conglomerates and volcanic ash-beds (or bentonites) occur. Caledonian (undeformed) lamprophyre dykes occur, the best example being at Ballyhalbert Pier (ESCR Site 424). The excellent structural (faulted anticline), stratigraphic (Ordovician - Silurian) and palaeontological (graptolites) site of Coalpit Bay is in this LCA: ASSI 105.
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 narrow strip of land shows that most of it is underlain by till associated with fast flowing Late Midlandian ice that moved across the region at the time of the drumlin readvance. Over most of the LCA this left a cover of drumlins orientated approximately in a southeasterly direction. In the majority of cases this has resulted in a thick layer of Upper (younger) Till overlying a core of Lower (older) Till. This pattern has been observed across Northern Ireland, apart from a limited area in the north of County Down, where Hill (1971) observed drumlins composed only of Lower Till. These occur in the very north of the LCA, to the west of Donaghadee, they are aligned approximately north to south and 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.
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. It is in such an inter-drumlin hollow at Roddans Port, that sediments have been found that allow the interpretation of post-glacial sea level change along the coast. These changes are reflected in the isolated raised beach deposits that are mapped along the coast. Generally they are the result of post-glacial flooding by a rising sea level, of a landscape that was still isostatically depressed following the disappearance of Midlandian ice. The coast is also backed along a considerable proportion of its length by blown sand.
Key Elements ASSI/ASIRoddans Port ASI
A sequence of terrestrial, late glacial sequence sandwiched between marine deposits in a former inter-drumlin hollow that includes peats, soliflucted material and up to 5m of red marine clays overlain by gravels forming a raised shore platform. The sequence has provided evidence of national importance for late- and post-glacial land and sea levels.
Other sites/units identified in the Earth Science Conservation Review424 Ballyhalbert Pier
Caledonide Igneous Complexes. Coastal exposure of relationships between Silurian country rocks and younger, undeformed lamprophyre dykes.
Outer Ards
The Outer Ards coast is of significance because of both its biological and geological attributes. Geologically, it is internationally important for the rock series that support the obducted accretionary prism model for the closure of the Iapetus Ocean in Lower Palaeozoic times. This contains the best developed and most historically important outcrop of Moffat Shales in Ireland. These are a condensed succession of grey or black, often richly fossiliferous, graptolite shales ranging in age from the Caradoc to Upper Llandovery. Interbedded with the shales are some fifty bands of bentonite clay, each representing a fall of fine grained volcanic material.