West Tayvallich Peninsula
Also within
Condition (NatureScot)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| F1 | Dalradian | Favourable | — | 2010-09-21 |
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
Rock Type: Limestone, Slate
Landscape processes: Coastal, Volcanic / Igneous
Description
West Tayvallich Peninsula West Tayvallich Peninsula SSSI occurs along the west coast of the Tayvallich peninsula, approximately 12 km west of Lochgilphead. The rocks of the site are assigned to the Dalradian Supergroup, which originated as ocean sediments before 570 million years ago. They represent the Tayvallich Subgroup of the Argyll Group and are deformed into a large downfold, the Tayvallich Syncline. This fold represents major rock structures affecting much of the south-west Grampian Highlands. Its shape causes successively younger rocks to occur south-westwards through the site. At the site’s northern end the Crinan Grit Formation, dominated by altered marine sandstones, records coarse sediment deposition in the ancient ocean. A reduction in this sediment is indicated by the succeeding Tayvallich Slate and Limestone Formation, which forms distinctive thin outcrops. South-west of Tayvullin the site is dominated by rocks formed from underwater eruptions, the Tayvallich Volcanic Formation. Outcrops show how underwater lava flows affected sea-floor sediments, notably around Port nan Clach Cruinn. Distinctive pillow-shaped lavas, and deposits of lava fragments called hyaloclastites, record how molten magma encountered seawater. The origin of the most exceptional deposit, the Loch na Cille Boulder Bed, is still debatable. Rock masses also solidified from sub-surface magma, such as that forming Rubha na h-Airde. The youngest rocks are altered sandstones called the Kells Grit, around Keillbeg. They are assigned to the lowermost Southern Highland Group of the Dalradian. This SSSI has considerable importance in the history of geology. Among its exceptional features, it has the best exposures of volcanic rock in the whole Dalradian of Scotland, and one rock mass has provided a rare and critical date of 600 million years ago. Above all, the site is nationally important because it superbly represents both an important part of the Dalradian sequence, and the rock structures that control its distribution. It helps reveal key aspects of how crustal plate movements created an ocean basin, and then destroyed it during formation of the Caledonian mountain belt.