Earth Science Conservation Review
| Annacramph Lane | Armagh |
| Site Type: | Inland exposure |
| Site Status: | ESCR |
| Council area: | Armagh District Council |
| Grid Reference: | H88634956 |
| Google maps: | 54.38687,-6.6362 |
| Rocks | |
|---|---|
| Rock Age: | Carboniferous (Asbian, Visean) |
| Rock Name: | Armagh Group |
| Rock Type: | Conglomerate, Limestone, Sand, Sandstone |
| Interest | |
| Fossil Groups: | Alga, Brachiopod, Foraminifera |
Summary of site:
This small locality is important because it shows rare evidence of exposure of the sea bed during the Asbian stage of the Carboniferous.
The rocks giving this evidence are sandwiched between medium-grained limestones and lime muds. The key beds are 1.3m of pale grey, fine to medium-grained sandstone, purple stained in part, topped by 0.2m of soft, thin layers of very fine sandstone with siltstones and mudstones. These beds have been channelled by water and the channels filled with coarse sandstones which themselves are channelled and filled with limestone boulders (up to 0.4m across) set in coarse quartz sand. A layer of purple brown mudstone follows, topped by layers of angular and rounded gravel and pebble-sized limestone fragments. These give way to regular beds of limestone at the top of the section. A thickness of only 8m of rock is exposed in a low cliff 25m long.
Pure limestone sediments like those dominating the Asbian stage around Armagh indicate warm shallow sea conditions, where the sediments form from the shells and skeletons of sea creatures far from land. The presence of layers of quartz sands and mud in such limestones is a clear indication of debris from nearby land but the water channelling and filling shown in these beds can only be explained by their emergence as land. The sandstone, mudstone and boulders choking the channels are all typical of this kind of environment.
The small outcrop allows little further interpretation but two other sites in the area, Rock Road Quarry and Drumarg Cliff, also produce fragmentary evidence of a similar kind.
The rocks giving this evidence are sandwiched between medium-grained limestones and lime muds. The key beds are 1.3m of pale grey, fine to medium-grained sandstone, purple stained in part, topped by 0.2m of soft, thin layers of very fine sandstone with siltstones and mudstones. These beds have been channelled by water and the channels filled with coarse sandstones which themselves are channelled and filled with limestone boulders (up to 0.4m across) set in coarse quartz sand. A layer of purple brown mudstone follows, topped by layers of angular and rounded gravel and pebble-sized limestone fragments. These give way to regular beds of limestone at the top of the section. A thickness of only 8m of rock is exposed in a low cliff 25m long.
Pure limestone sediments like those dominating the Asbian stage around Armagh indicate warm shallow sea conditions, where the sediments form from the shells and skeletons of sea creatures far from land. The presence of layers of quartz sands and mud in such limestones is a clear indication of debris from nearby land but the water channelling and filling shown in these beds can only be explained by their emergence as land. The sandstone, mudstone and boulders choking the channels are all typical of this kind of environment.
The small outcrop allows little further interpretation but two other sites in the area, Rock Road Quarry and Drumarg Cliff, also produce fragmentary evidence of a similar kind.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Annacramph Lane, County Armagh, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=278. Accessed on 2024-12-26 |
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