Craigyfulfran & Clarach
Also within
Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Geological Period: Silurian · Rock Type: Mudstone
Landscape processes: Coastal, Glacial, Karst
Description
Description The Craigyfulfran part of the site is of special interest on two scores: i) The site is the type locality for the Aberystwyth Grits, of Llandovery age. These rocks consist of a sequence of greywacke-mudstone rhythms with the latter lithology predominant. Greywacke units are thinner here than on more southerly sections of the Grits, indicating a greater distance from the source area for these turbidite-generated sediments. Soft-sediment deformation structures and hexagonal feeding-burrow systems assigned to the ichnogenus Palaeodictyon are common. These features, in combinations with fold and faults, make this a good teaching site. ii) The Aberystwyth Grits in the cliffs and foreshore here show complex structural features of special geological interest. These Silurian rocks were later subjected to intense and repeated compression during the Caledonian mountain building episode (orogeny). As a result of this compression the rock layers became contorted by complex folds and cut by numerous fractures. Exposures at Craigyfulfran provide unique examples of small-scale folds cut by an early cleavage (closely spaced parallel fractures), both of which apparently formed before the main fold and cleavage sets recognised throughout the region. These exposures also provide numerous small examples of slip surfaces developed parallel to the rock layers, an important element of the complex process by which the rocks distorted during the orogenic compression. This is an important locality for study of the effects of the Caledonian Orogeny in this region. Clarach is an important site on the West Wales coast with an uninterrupted sedimentary record from the start of the Late-glacial period to the present day. Studies of the lithostratigraphy, pollen and diatoms, supported by radiocarbon dating, have provided a detailed record of environmental and sea-level changes. A sequence of entirely freshwater deposits is succeeded by one in which marine influences associated with the rising sea-level during the Flandrian have been dated at about 6,000 BP. Remarks: Part of the site is owned by Ceredigion Council.