Killeter Uplands Geodiversity Profile

Outline Geomorphology and Landscape Setting

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 region described as Highlands and Lowlands of East Donegal. As such, the Killeter Uplands uplands have a broad, rounded land form, which is seemingly diminished in scale by extensive conifer plantations. The highest summit is Meenbog Hill at 271m. The area includes the upper reaches of the Mourne Beg River and the Derg, which flow within broad, shallow valleys. The upland summits have a simple, large-scale pattern of moorland, bog and extensive conifer plantations. The shapes of the plantations, and in particular the character of their edges, have a strong visual influence. Most are geometric blocks and they form hard, angular lines across the rounded slopes of the ridges. Within the valleys, patches of scrubby woodland, pastures and marsh form a more finely grained landscape mosaic. The landscape can therefore be summarised as one of broad ridges with rounded summits and wide, relatively shallow valleys.

Pre-Quaternary (Solid) Geology

The 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)

This LCA comprises a western tip of Northern Ireland. The geology is dominated by Neoproterozoic metamorphic rocks with minor Carboniferous. Covers part of the Pettigoe Plateau - ASSI 065.

The Dalradian comprises quartzose schists, grits, limestone beds and the "green beds" (chlorite - epidote schists). The Carboniferous succession is restricted to a faulted slice in the far southeastern tip of LCA19 where Ballyshannon Limestone, Bundoran Shale and Claragh Sandstone are recorded. The main Tertiary rock type of the area are north - south and NW-SE trending dykes Faulting is ubiquitous in the Dalradian and common in the Carboniferous. The Laghy Fault (NE-SW) crosses the northwestern part of LCA19.

Quaternary (Drift) Geology

Northern Ireland has experienced repeated glaciations during the Pleistocene period that produced vast amounts of debris to form the glacigenic deposits that cover more than 90% of the landscape. Their present morphology was formed principally during the last glacial cycle (The Midlandian), with subsequent modification throughout the postglacial Holocene period. Reconstruction of previous glacial cycles is difficult because any evidence is isolated and poorly constrained. The Late Midlandian, the last main phases of ice sheet flow occurred between 23 and 13ka B.P. 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 is often referred to as the Drumlin Event or Drumlin Readvance. Drumlin orientation, glacial striae and other evidence indicate ice flow from dispersion centres in the Lough Neagh Basin, the Omagh Basin and Lower Lough Erne/Donegal. It is important to note that the landforms and associated deposits derived from these processes are in most instances essentially fossil. Once damaged or destroyed they cannot be replaced since the processes or process combinations that formed them no longer pertain. They therefore represent a finite scientific and economic resource and are a notable determinant of landscape character.

This upland area was overridden by ice in the late Midlandian that has left a glacially scoured and rounded landscape that is for the most part drift-free and blanketed in peat. There are limited areas of till in the far northeast of the LCA where it extends into the Derg Valley. The till would have been deposited by Late Midlandian ice moving north/northeastwards across the area from an ice centre in the Omagh Basin. The only other significant deposits are spreads of alluvial material associated with the floodplains present-day rivers.