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'.
Between Newry and the Mourne Mountains in the south of the country, the Slieve Roosley landscape comprises a group of open, exposed hills with a rugged profile. These rise to 364m at Slieve Roe and include the surrounding farmed footslopes, which are dissected by river valleys. The Rostrevor Glen and Kilbroney River together form a marked feature along the eastern boundary of the area, which is underlain by a complex geology of igneous and sedimentary rocks. Key geomorphological elements in the east of the LCA are the glaciofluvial deposits of the Western Mournes complex. The moraines of this complex add topographic diversity to an area where the visual dominance of the Mourne mountains decreases rapidly westward and the drumlins around Rostrevor continue the trend of declining hilltop altitude towards the west and south, their clustered pattern and streamlined morphology contrasting with the isolated valley divides of bedrock highs. Glaciofluvial landforms in the rural, pasture-dominated landscape are generally intact and there are few excavations.
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 (Slieve Gullion Complex, Mourne Granites, dykes), about 55 million years old |
| Late Caledonian - Newry Complex, about 420 million years old |
| Lower Palaeozoic - Gala Sandstone, Hawick Group, between 450 and 420 million years old |
The area is to the east of Newry and comprises 60% Lower Palaeozoic, 20% Mourne Granite, 10% Newry Complex Granodiorites. The remainder is made up of Tertiary dykes.
Lower Palaeozoic greywacke sandstones were deposited in a deep marine environment and may have volcanic ash beds and conglomerates within.
The western boundary of LCA72 comprises an elongate outcrop (up to 1km wide) of Caledonian (probably Devonian - GSNI, 1997) Newry Granodiorite. The first and second phases of intrusion are present. The contact with metamorphosed Silurian is seen at Aughnagon Quarry (ESCR Site 419).
Tertiary-aged dolerite and felsite dykes occur throughout the area: most strike NW-SE within the Lower Palaeozoic succession. Far fewer dolerite dykes are observed cutting the Mourne granites, suggesting that the main emplacement of the Tertiary dykes was pre-granite.
Mourne Granites (Tertiary)
These Tertiary granites are known to have been intruded in five phases. G4 and G5 are present on the eastern edge of LCA72 as the area borders the Mournes. The G4 - G5 contact can be seen at the possible ASSI of Kilbroney River (ESCR Site 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 LCA shows a mix of drift free uplands dissected by a series of rivers draining southwestwards towards Carlingford Lough. The Drift map for the area shows the lowlands to be underlain by ice of a late-glacial readvance that was deflected westwards around the flank of the Mournes Massif before swinging eastwards to pass down Carlingford Lough. However, more recent fieldwork sponsored by the Department of the Environment (NI) has identified a series of important moraine ridges within the southwest draining valleys. These form part of the Western Mournes Moraine and Drumlin Complex that occupies the valleys of the Ghann, Moygannon and Kilbroney Rivers, as well as the Glen River and the upper Shanky's River. All contain recessional moraines associated with Late Midlandian ice retreat. They stand above the lowlands southwest of the Mournes that are characterized by southeastward trending drumlins. These are related to Late Midlandian fast ice flow into Carlingford Lough, through the western valleys of the Mournes and across the lowlands to the ice limit at Cranfield Point. This probably indicates rapid downdraw of marine-based ice. Chaotically distributed hummocks and occasional kettleholes on the lower slopes of the drumlins and in inter-drumlin areas record local ice stagnation. Other areas of the Complex occur in LCAs 69, 75 and 84.
Key Elements ASSI Deglacial ComplexesWestern Mournes moraine and drumlin complex.
The complex is considered to be of limited scientific value as the type of cross-valley moraines occurring in the complex are common in the Mourne Mountain valleys and moraine morphology is frequently indistinct.
Other sites/units identified in the Earth Science Conservation Review96 Gruggandoo
Tertiary.
105 Kilbroney River
Contact between G4 & G5 granites.
419 Aughnagon Quarry
Caledonide Igneous Complexes. Newry Igneous Complex. Outcrops showing relationship between contact metamorphosed Silurian country rock and granodiorite.
AONBAlmost all of the LCA lies within the Mourne AONB (1986). This designation is indicative of the scenic quality of the landscape.