An t-Sron

Geological Conservation Review site | GCR #1010 | Stratigraphy | Cambrian

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.

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Summary

A key site for developing understanding of the Cambrian succession in NW Scotland - important for north Atlantic correlations and, more locally, for reconstructing the structures of the Moine Thrust Belt

This is a key locality for establishing the stratigraphic order of Cambrian rocks in NW Scotland - the type locality for the An t-Sron Formation, and its constituent members of the Fucoid Beds and Salterella Grit. The headland holds an antiform cored by the Pipe Rock (Eriboll Sandstone Formation), passing up through the An t-Sron and into the lowest part of the Durness Group carbonates. Building the lower part of the Cambrian stratigraphic section requires understanding the significantly more complex steep, eastern limb (locally over-turned, with thrust repetition) of the Kempie syncline.The Fucoid Beds and Salterella Grit are well-displayed, the two latter units yielding the typical fossils (olenellid trilobites and other taxa) enabling a Lower Cambrian age to be assigned to these rocks. The facies transition from tidal arenaceous units to the overlying calcareous formations of the Durness Group has been studied in detail and related to the overall palaeogeographic development of the region in Cambrian times. A key site in our understanding of the Cambrian rocks of northern Britain.

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Related geosites

Overlaps with

A small fold in a broken block of quartz arenite of the Pipe Rock Member

Alex Gabriel

Sept. 16, 2023

NC 44326 58132

Joined fine-grained quartzite beds of the Pipe Rock Member with visible Skolithos burrows

Alex Gabriel

Sept. 16, 2023

NC 44326 58132

The boundary between the Pipe Rock Member (light grey, in the middle ground) and the Fucoid Beds (brown-orange, on the cliff). The contact can be traced from the center of the image to the left at the base of a thin, weathered unit overlain by massive sandstones.

Alex Gabriel

Sept. 16, 2023

NC 44171 58138

The lowermost unit of the Fucoid Beds is represented by fine-grained, orange-brown sandstones that were intensely weathered.

Alex Gabriel

Sept. 16, 2023

NC 44159 58129

Higher up in the sequence, the sandstones are less weathered. Small-scale hummocky cross-stratification and bioturbation are present.

Alex Gabriel

Sept. 16, 2023

NC 44159 58129

A tight fold in the Fucoid Beds

Alex Gabriel

Sept. 16, 2023

NC 44142 58127

Bimodal cross-lamination in the Fucoid Beds

Alex Gabriel

Sept. 16, 2023

NC 44142 58127

Swaley cross-stratification and ripple lamination in the Fucoid Beds

Alex Gabriel

Sept. 16, 2023

NC 44112 58124

Layers of Fucoid Beds appear to have been deformed into a large recumbent fold.

Alex Gabriel

Sept. 16, 2023

NC 44112 58124

Underside of a slab of Fucoid Beds displaying Planolites burrows

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Sept. 16, 2023

NC 44109 58125

Boundary between the Fucoid Beds (below) and the Salterella Grit (above). The wave-cut platform at the base of the Fucoid Beds preserves traces of interference ripples. View looking northeast

Alex Gabriel

Sept. 16, 2023

NC 44003 58089

Thin dolomitic limestones of the Ghrudaidh Formation with a 40-degree southwest dip

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Sept. 16, 2023

NC 43979 58074