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 Ballygowan Drumlins area is underlain by Silurian rocks which have been covered by glacial deposits. The smooth, rolling drumlin landforms create a dynamic landscape pattern. Ground levels fall gradually towards Strangford Lough and in more low-lying areas, the drumlins exhibit a relatively waterlogged character (and with amore extensive network of watercourses than amongst the drumlins of the adjacent Castlereagh Plateau). Loughs and damp woodland are found within lowland hollows between drumlins, providing an organic landscape element within a relatively regular landscape pattern. These marshy patches make a valuable contribution to the diversity of the landscape.
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 - various intrusives, about 55 million years old |
| Triassic - Sherwood Sandstone Group, about 220 million years old |
| Permian - Enler and Belfast Group |
| Lower Palaeozoic Silurian (Hawick Group) |
| Ordovician - Gala Sandstone. Moffat Shale |
Predominantly Lower Palaeozoic greywackes and shales with numerous minor igneous intrusions. 80% of the LCA comprises Lower Palaeozoic (Ordovician) Gala Group: the northern 15% of the LCA comprises Permian and Triassic, the remainder being Tertiary intrusives. The NE -SW strike of the Lower Palaeozoic Ordovician and Silurian beds at outcrop is produced by faulting and belies the fact that minor folds occur within each fault tract. North - south faults cross-cut and thus post-date earlier faults. 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 onglomerates and ash-beds (or bentonites) occur.c
The Permian - Enler & Belfast Group comprises red-brown sandstones, conglomerates, siltstones. A basal breccia, equivalent to the "brockram" of northern England is found at the base (1 - 50cm thick), here termed the Newforte Breccia Formation, the only outcrop of which is Ballyrainey (ESCR Site 261). The Belfast Group comprise calcareous mudrocks with thin sandstone and anhydrite lenses resting conformably on Enler Group, a gradual transition between the two groups occurs.
The Triassic - Sherwood Sandstone Formation comprises red, purple and brown cross-stratified sandstones, siltstones with minor clay beds and partings. The sandstones are either soft and poorly-consolidated or well-cemented where they are and have been exploited for building stones in the past. These sandstones are well-exposed in the quarries of Scrabo Country Park (ASSI 091).
NE - SW trending lamprophyre dykes and NW-SE trending dolerite dykes occur throughout the area. The age of some of the lamprophyres is not proven as Tertiary. A Tertiary sill occurs in the north of the area where it forms the top of the crag and tail hill of Scrabo itself (ASSI 091).
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 flowed southeastwards from an ice divide that lay approximately SW-NE along the line of the north Belfast Hills. Evidence for this flow direction is found in the orientation of the numerous drumlins that make up much of the landscape. However, within the LCA there are also significant outcrops of drift free bedrock that were scoured by the overriding ice. McCabe and Knight (in Knight 2002) have suggested that this area, and much of central Co. Down, was the site of an ice stream during the Drumlin Readvance that delivered a high sediment flux to the ice margin at areas such as the Lecale Coast to the southeast. This may go some way to explain the partial drift cover in the region and the widespread occurrence of rock cored drumlins. 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. Where drumlins are rock cored there may have been significant frost shattering prior to their shaping by ice flow. It is possible therefore to see tails of shattered debris within till leading away from the feature in the direction of flow (Davies and Stephens 1978). 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. 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. 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. Much of the infilling probably occurred early in the Holocene, as the landscape adjusted to increasingly temperate conditions. However, erosion may also have been accelerated in historical times, when rural population densities were considerably higher and much of the lowland landscape of Northern Ireland was more intensively cultivated. Whatever the stimulus for erosion and deposition, the sediments within these hollows typically contain an important record of local environmental change.
In the north of the LCA, the drift geology map highlights glaciofluvial deposits associated with late-glacial deposition by meltwater along the Enler Valley between Belfast and Comber - the so-called 'Dundonald Gap'. Smith et al. (1991) describe these deposits as mounded outwash that consists of laminated sand and gravel with subordinate red clays. The map also identifies alluvial sediments infilling inter-drumlin hollows and overlying the glaciofluvial deposits of the Enler Valley.
Key Elements ASSI034 STRANGFORD LOUGH PART 3
Extensive mudflats, saltmarsh and other types of shoreline habitat, including The Dorn (NNR), a unique and exceptionally important site for intertidal flora and fauna.
Other sites/units identified in the Earth Science Conservation Review261 Ballyrainey
Mesozoic. Only exposed outcrops of Newforte Breccia Formation in Northern Ireland.
AONBsA small part of this LCA on its eastern margin overlaps with the Strangford Lough AONB (1972). This designation is indicative of the scenic quality of this area of landscape.