Barf and Thornthwaite
Also within
Condition (Natural England)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| NY217265 | — | Favourable | 22.79 | 2024-02-21 |
Geology & landscape
Geological Period: Ordovician
Description
Description Barf and Thornthwaite consists of an area of hilltop crags and screes on the western side of Bassenthwaite Lake, about six kilometres north west of Keswick. The crags provide exposures of mudstones, siltstones and sandstones belonging to the upper part of the Loweswater Formation of the Skiddaw Group. These sediments represent turbidites deposited in an unstable shelf slope setting on the margin of the eastern Avalonian micro continent. The mudstones present in these exposures and amongst the surrounding screes represent periods when rates of deposition were relatively low. The mudstones contain a rich assemblage of graptolites representing the Didymograptus simulans Biozone of the Moridunian Stage of the lower Ordovician, Arenig Series. About twenty species of graptolite have been recorded from this site and for three species including D. simulans, this is their type locality. The relative abundance and high diversity of graptolites at this site means that it is of significance for the understanding of stratigraphical correlations between rocks of lower Ordovician age within southern Britain. Because of the oceanward position of this site, the graptolite fauna is in part cosmopolitan. The mix of cosmopolitan and provincial elements at this site give it great significance for the international stratigraphical correlation of lower Ordovician rocks particularly with Scandinavia at a time of maximum continental fragmentation and dispersal. The site is therefore of great significance for future studies of this aspect of Ordovician geology.