Aonach Beag and Geal-Charn
Geological Conservation Review site | GCR #3320 | Structural and Metamorphic Geology | Dalradian
Scotland's geosites are chosen because of their local, national or international importance. Take only photos, leave only footprints: avoid causing any damage to this site. You can walk almost anywhere in Scotland without the need to ask permission or keep to paths, but you have a responsibility to care for your own safety, to respect people's privacy and peace of mind and to cause no damage.
This site is a Site of Special Scientific Interest (SSSI). It is an offence to intentionally or recklessly damage the protected natural features of a SSSI, and this includes unauthorised sample collection.
The right of access does not extend to quarries, building sites or any land where public access is prohibited, or to the collection of geological samples.
Summary
The Aonach Beag and Geal-charn GCR site is of national importance for the way in which the complex Caledonian deformation pattern in a crucial central area of the Grampian Highlands can be related to the original geometry and subsequent development of early Dalradian sedimentary basins.
The site preserves excellent exposures of the stratigraphical relationships between the Kinlochlaggan succession and the underlying Grampian Group in a regional zone of steeply dipping rocks known as the Geal-charn - Ossian Steep Belt. The mountainous nature of the site is such that truly three-dimensional observations can be made of the structural geometry of the steep belt. The Lochaber, Ballachulish and Blair Atholl subgroups of the Appin Group are all represented in the upward facing Kinlochlaggan succession. This succession includes the Kinlochlaggan Boulder Bed, which occurs within the Lochaber Subgroup and thus is not equivalent to the Port Askaig Tillite on Islay. The site also provides an excellent cross-sectional view of the complex Kinlochlaggan Syncline and other complementary tight folds that form the core of the steep belt.
The Geal-charn-Ossian Steep Belt occurs at the boundary between contrasting structural and stratigraphical domains. Distinct but coeval sedimentary successions in each domain responded in fundamentally different ways to later deformation, with primary upright structures to the west and recumbent structures to the east. The steep belt is a zone of primary major upright folds with associated slides, developed on severely attenuated fold limbs as originally stated by Thomas (1979). However, it is not a root zone to divergent nappes as envisaged by Thomas (1979), nor is it the sole product of a late monoform or late upright shearing as proposed by Temperley (1990). It occurs at the eastern margin of a thick composite sedimentary basin where deformation was focused against a footwall -high-. Subsequent deformation was then influenced by the distribution of half-graben fills and intrabasinal -highs-.
Related geosites
In collections:
There are no photographs yet