Dob's Linn
Geological Conservation Review site | GCR #2001 | Stratigraphy | Llandovery
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
This hidden mountain gorge is named after a Covenanter's hideaway during the ‘Killing Times’ of the 17th.C. This 'Classic' locality was where Charles Lapworth, after studying and sorting the graptolite fossils that are readily found in the shale cliffs here. The biostratigraphy at this site contains the layer recognised internationally as the boundary between the Ordovician and Silurian Periods.
The site is one of Britain's most important stratigraphic localities.
It shows the standard section for the base of the Llandovery Series and the Global Stratotype Section and Point (GSSP) for the base of the Silurian Period - and so forms the Ordovician/Silurian boundary. Its graptolite-rich sequence here shows a graptolite zonation (from the persculptus to the maximus zones) spanning the Ashgill- Llandovery boundary, and including the Upper Hartfell Shale, Birkhill Shale and Gala Greywacke.
A review in 2006, approved by the International Commission of Stratigraphy (ICS) and ratified by International Union of Geological Sciences, re-confirmed the GSSP to be at 1.6 m above the base of the Birkhill Shale at the Linn Branch trench in Dob's Linn. The definition of the boundary was adjusted and revised in this review. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, is now regarded as the biostratigraphic mark for the base of the Silurian.
Site information
Access
Dob’s Linn is in a narrow mountain gorge, 0.5km walk (to the NW) off the A708, Moffat-to-Selkirk road. There is limited roadside that can hold 4/5 cars, or 2 minibuses. NT 196 154.
It is also 1.5km NE from the National Trust for Scotland (NTS) Car Park at 'The Grey Mare’s Tail' NT 186 145. (with a small charge unless NTS/NT member).
Although close to a road, the site is fairly remote in hill country with no immediate facilities available. Nearest café/toilets are at Moffat, or the Glen Café, near St. Mary’s Loch (and may have limited seasonal opening).
The walk to the site, from both the layby off the A708 or from the NTS carpark, is over rough & inclined fell-side, and stoney ground. It involves crossing small streams (1m wide).
To obtain a close-up view of the Ordivician / Silurian Boundary ‘Golden Spike’ requires clambering 50m up a very steep, slippery grass/craggy slope. Great care is required.
There is No physical marker for the 'Golden Spike'.
Further information
https://earthwise.bgs.ac.uk/index.php/Dob%27s_Linn,_Moffat_…
McAdam, A.D., Clarkson, E.N.K. and Stone, P. eds., 1992. Scottish borders geology: an excursion guide. Scottish Academic Press.
https://earthwise.bgs.ac.uk/index.php/Dob%27s_Linn_-_an_exc…
Williams S. Henry, Lawson J D 1992 Dob's Linn - an excursion. : Geological excursions around Glasgow & Girvan.
https://sitelink.nature.scot/site/1172
Moffat Hills SSSI
https://archive.org/details/LapworthMoffatSeries1878QuJouGe…
Lapworth C 1878 The Moffat Series Qu Jou Geol Soc Vol 34
https://www.episodes.org/journal/view.html?volume=31&number…
Rong, J., Melchin, M., Williams, S.H., Koren, T.N. and Verniers, J., 2008. Report of the restudy of the defined global stratotype of the base of the Silurian System. Episodes Journal of International Geoscience, 31(3), pp.315-318.
Site highlight
This is a relatively accessible location with a short walk-in to readily view graptolite fossils.
It is a Classic’ geo-site due to Charles Lapworth historical work, and is one of Britain’s most important bio-stratigraphic localities. It is recognised by the International Commission of Stratigraphy (ICS) that the Global Stratotype Section and Point (GSSP) or ‘Golden Spike’ for the Ordivician / Silurian Boundary is located 1.6 m above the base of the Birkhill Shale, located at the north cliff trench above the Linn Burn.
Safety notes
The site is in Scottish hill country, adverse weather is always a potential factor – be prepared for rapid changes.
Phone signal in the Linn may be limited.
The terrain can be slippery in wet weather, and stream crossings can be more hazardous if in spate, and should be avoided. A walking stick may be an advantage for stream crossings.
Fossil-bearing horizons are often on steep loose unstable shaley ground.
Related geosites
Overlaps with:
John Robson
Sept. 3, 2023
View of Moffat Water Valley looking SW
John Robson
Sept. 3, 2023
Looking NE into Dob’s Linn
John Robson
Sept. 3, 2023
Dobb's Linn waterfall above the Linn Burn branch of the Moffat Water.
John Robson
Sept. 3, 2023
Looking toward the Ord-Sil Boundary at the North cliff trench, above the Linn Burn branch of the Moffat Water.
John Robson
Aug. 21, 2021
Ord-Sil Boundary at the North cliff trench above the Linn Burn branch of the Moffat Water.
John Robson
Sept. 3, 2023
Graptolite fossils