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 Antrim Plateau and Glens. This upland area is dominated by a series of structural plateaux that dip gently in towards the Lough Neagh Basin. Detailed topography is largely controlled by a succession of Tertiary basalt lava flows that define successive, large-scale steps within the landscape. The plateaux are separated from each other and their frequently dramatic margins are fretted by often fault-guided, steep-sided glens. Recession of the plateaux margins in the north of the region around Fair Head has exposed the underlying Palaeozoic basement. The plateaux margins are typically characterised slope failures that range from large rotational landslides to individual blockfalls.
Fair Head comprises a narrow coastal strip between the Antrim Plateau and the sea and includes the lower slopes of Greenanmore, Carnanmore and Carnaneigh. The interesting topography of the area results from its complex underlying geology of schists and basalts with igneous intrusions giving rise to prominent cliffs and headlands. The various geological strata have led to the development of cliffs of striking contrasts in colour and form. Short steep streams drop from the plateau to small, secluded bays such as Murlough Bay. Fair Head itself, is one of the most striking features in the Tertiary igneous rocks of the Antrim coast. The headland is a sill, mainly composed of dolerite which was intruded horizontally during the Tertiary into gently dipping lower Carboniferous shales. Erosion of the overlying limestone beds has left the sill as a dramatic promontory. Vertical jointing of the dolerite forms impressive columnar structures that emphasise the sheerness of the cliff face. The cliffs at Fair Head rise approximately 120m above sea level and are fronted by an apron of talus slopes comprising accumulated debris from toppled and fractured columns. The talus or block scree thatsurrounds the foot of Fair Head is thought to be primarily of late- and post-glacial age because Scottish ice advancing across the North Channel of the Irish Sea would almost certainly have removed any pre-glacial debris.
Fair Head is best described as a coastal 'pivot point' marking the boundary between the Atlantic Ocean and the Irish Sea as well as a change in coastal form from a north to south to an east to west orientation. The surface of the Fair Head sill shows evidence of glacial erosion in the form of roches moutonnees and glacial striae. Both of these features occur around Lough na Cranagh with striae trending north-north-east.
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 | Intrusives (Fair Head Sill - about 55 million years old) |
| Cretaceous | Hibernian Greensand & Ulster White Limestone - about 100 million years old |
| Carboniferous | limestones and coal measures - about 350 million years old |
| Neoproterozoic (Dalradian) | Murlough Bay, Torr HeadLimestone, Owencam metamorphic formations - about 550 million years old |
This LCA extends from Ballycastle to Fair Head, Murlough Bay, Torr Head and Runabay Head. The geology comprises a mix of Neoproterozoic metamorphic, Carboniferous and Mesozoic sedimentary and Tertiary igneous rocks in faulted and unconformable contact.
The NE Antrim Neoproterozoic Dalradian was originally layers of sediments and volcanic beds that have been buried and metamorphosed. Exposed on the crags at Benvan (ESCR Site 339). Limestones in the succession have been converted to marbles such as the Torr Head Limestone exposed at Escort Port (ESCR Site 340) and Torr Head (ESCR Site 341).
The succession is also exposed at Carnaneigh Point (ESCR Site 344 and Loughan Bay (ESCR Site 345). The Leckpatrick Green Beds type location (Leckpatrick Point) is also in this LCA - ESCR Site 343. Altmore Formation ESCR Site 342.
The Carboniferous succession comprises laterally lavas, pillow lavas and limestones at the base, passing up into laterally more continuous sandstones and coals (with one correlatable limestone succession). The basal pillow lavas are exposed at the northwestern edge of LCA120. ASSI 147.
The Cretaceous succession is found below the Fair Head Sill on its eastern outcrop. Murlough Bay ( ESCR Site 296) also encroaches into this LCA.
The main Tertiary rock type of the area is the Fair Head Sill ( ESCR Site 90), at the centre of the LCA.
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.
Most of coastal margin of this LCA is underlain by drift free bedrock and marked by a series of large landslips to the east of Fair Head and in Murlough Bay. These represent a combination of post-glacial adjustment to the removal of ice that butted against what was to become the coastline, and ongoing marine erosion at the cliff foot. In the northwest of the LCA, where it borders on the Carey Valley, Late Midlandian till underlies the landscape derived from an ice mass that moved northwards from a centre in the Lough Neagh Basin. Superimposed on this till in the northwest of the LCA is an area of fluvioglacial deposits that are an extension of the Carey Valley Delta Complex) This consists of variable stratified sands and gravels that occur along the axis of the Carey Valley as a northward thickening wedge of sediment.
Key Elements ASSI147 BALLYCASTLE COALFIELD
Ballycastle Coalfield is the best exposure of a coalfield sequence in Ireland. It contains a series of Carboniferous sedimentary rocks (335-330 million years old) with contemporary lavas and younger Tertiary igneous rocks (60 M.y.). The sedimentary rocks were deposited in a shallow marine bay which gradually developed into a vegetated coastal swamp subject to periodic flooding by the sea. The vegetation was preserved as seams of coal. Fossils that have been found include goniatites (shellfish), fish remains, giant clubmosses and arthropod insects. The Tertiary dykes have metamorphosed the carboniferous shales to produce porcellanite and a range of minerals. The site also contains evidence of early industrial activity: the coals and iron ores were mined between the 16th and 19th centuries.
Deglacial ComplexesCarey Valley Delta Complex
The Carey Valley delta is a site of excellent scientific importance within the context of Northern Ireland and records a high relative sea level of approximately 100m O.D. This fact is of extreme value in the reconstruction of Irish Sea basin conditions upon deglaciation of the coastal shelf. It indicates significant downwarping of the Irish coast at this location.
Other sites/units identified in the Earth Science Conservation Review339 Benvan
Precambrian. Argyll Group. Accessible outcrops of representative strata of Owencam Formation.
340 Escort Port
Precambrian. Argyll Group. Representative strata of Torr Head and Owencam Formations.
341 Torr Head
Precambrian. Stratotype for Torr Head Formation - key marker of Dalradian in NE Antrim. Best exposure of Middle-Upper Dalradian boundary.
342 Altmore Burn
Precambrian. Follows line of Altmore Fault. Outcrops of coarse quartz-feldspar grit and psammite lithologies of the Altmore Formation. Exposures of Leckpatrick Green Beds.
343 Leckpatrick Point
Precambrian. Southern Highland Group. Coastal exposure of stratotype of Leckpatrick Green Bed Member, defining the stratigraphic base of Runabay Formation.
344 Carnaneigh Point
Precambrian. Runabay Head Formation. Contains potential stratotype for Carnaneigh Green Bed Member.
345 Loughan Bay
Precambrian. Southern Highland Group. Outcrops of siliclastic and volcanogenic lithologies of Runabay Head Formation. Examples of albite and tourmaline bearing schists.
296 Murlough Bay
Palaeontological. Late Cretaceous basal conglomerates exposed beneath Ulster White Limestone cliffs. Contains macrofossil evidence for Lower Jurassic strata much younger than those preserved onshore.
90 Fairhead
Tertiary. Dominant headland. Thickest and most extensive Tertiary sill associated with lava plateau of NE Ireland. Visible record of intrusion processes with transgression from Carboniferous to Cretaceous.
AONBAll of this LCA lies within the Antrim Coast and Glens AONB (1988).