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 can be viewed naturally as an extension of the region described as the Central Lowlands, although it extends southwards into the adjacent region of the Uplands and Drift Covered lowlands of Down and Armagh. This region owes its large-scale morphology to the early Tertiary subsidence of the Lough Neagh basin into the magma chamber from which the basalts that underlie much of the landscape originated. This has produced a largely centripetal drainage system from the rim of the basin into Lough Neagh that ultimately drains northwards via the Lower Bann. To the south of the Lough Neagh basin, the lowlands extend southwestwards along a Caledonian structural trend into the Monaghan-Clones depression. In the east of the region the lowlands extend northeastwards along the fault-guided Lagan Valley. There are no strong topographical barriers in the region and boundaries between LCAs tend to be subtle. The low gradients of the rivers, especially on the clay lowlands immediately around Lough Neagh, create inherent drainage problems and frequently it is only the slopes of the many drumlins that provide permanently dry sites. The Lough Neagh Basin was a major ice accumulation centre during the Late Midlandian and much of the lowland areas to the north and south of the Lough are dominated by extensive drumlin swarms.
The Upper Bann Floodplain LCA follows the course of the Upper Bann between Scarva and Portadown. The area includes the extensive areas of moss on the river floodplain at Terryhoogan Moss, Park Bog and Brackagh Bog. A railway line follows the course of the river between Scarva and Portadown. The landscape consists of well-defined, broad river terraces containing large pastures above Dynes Bridge and extensive areas of moss on former river meanders. At Portadown, built development is a dominant local influence. The river floodplain is the most attractive landscape feature in the area and is an important focus for views and recreation. The River Bann has been constrained by flood embankments (often 6m high) and many smaller banks and straight drainage ditches run laterally towards the river across the adjacent pastures.
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 - Lough Neagh Group, about 20 million years old |
| Tertiary - various intrusives & Lower Basalt Formation, about 60 million years old |
| Ordovician (predominant) - Moffat Shale, Gala Group and Gilnahirk Group, about 450 million years old |
Comprises two ages of rock strata and numerous minor igneous intrusions. 70% of the LCA comprises Lower Palaeozoic (predominantly Ordovician) greywacke sandstones and shales, the remainder being an outcrop in the north-west of Tertiary Lough Neagh Group mudstones and lignites
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.
As would be expected in the floodplain of a significant river, the drift geology map for this LCA shows that much of the landscape is underlain by alluvium. Beneath this is a cover of Late Midlandian till deposited by ice flowed southwards from an accumulation centre over the Lough Neagh Basin. Associated with this till are numerous drumlins that formed in and beside the Poyntz Pass glacial drainage channel. This formed during the deglaciation of the Lough Neagh lowlands, when there was a period when downwsting ice occupied the Lower Bann valley and prevented the northwards drainage of the proto-Lough Neagh. Lake levels then rose until an alternative outlet was found to the south via Pontz Pass and Newry to Carlingford Lough (Davies and Stephens 1978). McCabe and Hirons (1986) have described this drainage channel as having similarities to a tunnel valley system, in which sand cored drumlins occur within the channel system itself and are flanked by large rock drumlins west and east of the channel.