The weathered limestone slopes of Ben Suardal offer a glimpse of an ancient tropical sea. Look closely at the grey rock surfaces for silicified gastropod coils, standing out in the harder cherty material. These elusive fossils belong to the Ordovician part of the Durness succession, long before the Jurassic fossils better known from Skye’s shores.
FIND FREQUENCY: ♦♦ – Fossils are infrequent and often incomplete; patient examination of weathered surfaces is more useful than a hurried search.
CHILDREN: ♦♦ – Uneven, fissured limestone and steep grassy slopes make this unsuitable for young children.
ACCESS: ♦♦ – A short but uneven climb from the roadside was described in the original visit; check present conditions before setting out.
TYPE: Inland limestone outcrops and weathered blocks, within a protected landscape.
DIRECTIONS
♦ The approach is from the Broadford–Torrin road, the B8083, below the limestone slopes of Ben Suardal. The route recorded in 2007 describes a lay-by beneath the outcrop, with the valley between the hills opposite as an orientation aid. The parking place and approach have not been verified for this update.
♦ From a lawful parking place, the old route is a short climb towards the exposed limestone. Check signs and ground conditions, avoid passing places and gateways, and do not assume every roadside widening is suitable for parking.
♦ The published reference is 57.21526°N, 5.92594°W. This is a general locality reference, not a verified parking coordinate or a precisely surveyed fossil-bearing block.
FOSSIL HUNTING
Seek the landowner’s permission before taking fossils, and check the SSSI requirements described under Access Rights. Until collecting arrangements are confirmed, explore the locality through observation and photography, leaving the rock surfaces intact. There is still much to see without breaking the limestone.
Concentrate on naturally weathered surfaces where the softer carbonate has receded around harder silica. Fossil outlines can stand slightly proud of the grey limestone, but they are not always complete or obvious. A hand lens and photographs from several angles can reveal details that disappear when the rock is viewed straight on. Avoid stripping lichen, digging out vegetation or scraping the limestone to expose more material.
Gastropods are the most readily recognisable finds illustrated from this locality. Look for a curved whorl continuing into a coil, or a section through several whorls, rather than assuming that every rounded chert nodule is a shell. Many fossils are incomplete sections within the rock: a fragment of a spiral may be all that is visible. The original observations favour the south-western side of the exposure, but this is a search clue rather than a mapped collecting area.
Chert is silica-rich material that resists weathering more effectively than the surrounding limestone. It can preserve fossil shapes, but irregular cherty lumps also occur without recognisable organic structure. Photograph both a close view and the surrounding rock, with a scale beside the feature, so that any later identification retains its geological context. Do not assign a species from the appearance of a partly exposed coil alone.
The wider Ben Suardal limestone has a substantial scientific fossil record, but published samples from the formation are not necessarily from the exact hillside visited in this guide. Consequently, the names in regional research should not be treated as a guaranteed checklist for these particular blocks. Any unusual fossil is best recorded in place and referred for specialist advice before preparation or removal.
Scientific milestones in understanding Ben Suardal and its fossil-bearing limestone.
1888 – Fossils establish the limestone’s ancient age
Archibald Geikie published fossil evidence from Ben Suardal linking its limestone to the Durness succession, overturning the older assumption that these rocks were Jurassic. His account also interpreted the hill’s disturbed limestone as having been pushed westwards. The precise roadside knoll was not identified as the collection point.
1907 – Limestone and thrust described in detail
Geological Survey work distinguished the Ben Suardal Limestone and described the thrust carrying older sandstone above it. Fossil-bearing bands were recorded around the hill, although their positions were not consistently resolved into a measured succession.
1972 – Ben Suardal Limestone given formation status
Harry Whittington recognised the Ben Suardal Limestone as a formation in the correlation of British Ordovician rocks, formalising the local name used in subsequent palaeontological work.
2010 – Correlation with Croisaphuill documented
Robert Raine’s doctoral study correlated outcrops around Ben Suardal with the Croisaphuill Formation at Durness using their lithology and fossils. The study also examined Loch Lonachan separately.
2024 – Local stratigraphic scheme reassessed
M. Paul Smith, Robert Raine and John Repetski used the Croisaphuill correlation for the Ben Suardal Limestone and recommended replacing the separate Strath Suardal member scheme with the standard Durness Group formations where these can be recognised.
GEOLOGY
The pale limestone and dolostone belong to the Durness Group, a thick carbonate succession deposited on the margin of the ancient continent Laurentia. The original sediment accumulated in warm shallow seas; later alteration converted some limestone to dolostone and replaced parts of the sediment and fossils with silica. The contrast between carbonate and resistant chert helps explain why fossils can become visible on weathered surfaces today.
Ben Suardal has been described using several stratigraphic schemes. The BGS Lexicon retains a Ben Suardal Member within the Strath Suardal Formation, whereas the 2024 synthesis of the Durness Group correlates the Ben Suardal limestone with the Croisaphuill Formation of the standard northern succession. These are alternative interpretations and names for the relevant rocks, not separate layers to be stacked above one another. The fossils are Ordovician; describing this exposure simply as Cambrian obscures that distinction.
The present landscape also records deformation and erosion long after the shells were buried. Geological Survey work described older Torridonian rocks thrust over the limestone around Ben Suardal. The wider Strath district was subsequently affected by Palaeogene intrusions, locally converting limestone into marble, but the degree of alteration varies. It would be misleading to assume that every fossil-bearing block here is marble or to transfer a neighbouring intrusion’s effects to an unexamined exposure.
Rainwater gradually dissolves carbonate along joints and bedding surfaces, leaving fissures and uneven limestone pavement while resistant chert remains prominent. This is part of a protected limestone landscape, with vegetation rooted in cracks and pockets of soil. The visible blocks do not provide a measured, continuous section through the whole Durness Group: regional formation thicknesses should not be mistaken for the height or thickness of this hillside exposure.
Explore the Ordovician limestone, chert and geological structure at Ben Suardal.
DURNESS GROUP
The fossil-bearing carbonate rocks at Ben Suardal belong to the Durness Group. This succession accumulated on the marine margin of Laurentia, the ancient continent that included north-west Scotland. The group as a whole spans Cambrian and Ordovician time, but its full age range must not be applied to this particular outcrop.
Croisaphuill Formation correlation: the Ben Suardal Limestone
Recent research correlates the historically named Ben Suardal Limestone with the Croisaphuill Formation. Older maps and the BGS Lexicon use Ben Suardal Member within the Strath Suardal Formation; the Lexicon assigns an Arenig age. A 2024 revision recommends abandoning the local member scheme because some distinctions reflect metamorphism rather than consistent sedimentary units. These are alternative classifications of the rocks, not successive layers exposed here. Ordovician is the appropriate period label; a precise stage or numerical age has not been established for this small roadside exposure.
Limestone and chert
The historical Ben Suardal Limestone is generally dark grey internally and pale grey when weathered. The Survey described small black chert nodules and bands, commonly about 13–25 mm thick, together with pale, intersecting tubular markings interpreted as worm traces. These are descriptions of the wider unit, not a measured sequence at the roadside knoll.
A documented specimen from the knoll on the north-west side of Ben Suardal contains abundant chert standing above the weathered carbonate surface. Its host rock was identified as calcite-rich limestone, illustrating why not every exposure should automatically be called dolostone. Resistant chert and silicified fossil fragments remain prominent as the surrounding carbonate weathers.
Fossil-bearing surfaces
The original field guide records incomplete gastropod coils projecting from the rock, with rarer other molluscs and sponge remains. Irregular chert alone is not a secure fossil identification. Detailed brachiopod studies concern the wider Ben Suardal Limestone and should not be treated as a species checklist for this knoll.
Structure and limits of the section
Older Torridonian sandstone was thrust over the carbonate rocks around Ben Suardal. Folding and thrusting complicate the outcrop pattern, so adjacent rock patches do not necessarily represent a simple upwards succession. No reliable bed-by-bed log, local thickness or named fossil horizon has been established for the roadside exposure. The measured Croisaphuill sections at Durness and the fossiliferous bands around Loch Lonachan and Torran are separate localities.
References
Smith, M. P., Raine, R. J. & Repetski, J. E. (2024), Stratigraphy and faunas of the Durness Group.
Raine, R. J. (2010), The Durness Group of NW Scotland, section 1.2.9.
British Geological Survey, Ben Suardal Member.
Peach, B. N. and colleagues (1907), The geological structure of the North-West Highlands of Scotland, chapters 28 and 39.
Wilson, G. (2022), Durness limestone with chert, Isle of Skye.
SAFETY
The main hazards are steep grassy ground, loose blocks and uneven limestone with cracks and sharp edges. Wet rock and vegetation can be slippery; keep to stable ground and avoid climbing over outcrops simply to reach another fossil. Take particular care at the roadside and keep clear of traffic when leaving or returning to a vehicle.
Do not enter caves or deep fissures as part of this visit. Carry suitable navigation and let someone know your route and expected return time; do not rely on a mobile signal. Turn back if weather, visibility or the ground makes the approach unsafe.
EQUIPMENT
Sturdy boots, weatherproof clothing, a hand lens and a camera are the useful essentials. Carry a small scale for photographs and note the position and rock surface of each observation. Heavy hammers, chisels and sledgehammers are inappropriate for an unpermitted visit to these protected limestone outcrops.
CLEANING AND TREATING
Do not clean, chip or otherwise prepare fossils on the protected outcrop. For a specimen already lawfully held, start with careful examination and gentle dry brushing; hard chert and carbonate do not necessarily separate along the fossil surface. Forceful hammering can destroy the very coil or shell outline you are trying to reveal.
Avoid household acids, bleach and varnish. Laboratory acid extraction used in scientific studies is a controlled specialist process, not a recommendation for home treatment. Preserve the specimen’s locality information and seek advice before working on anything unusual or potentially important.
IDENTIFY YOUR FINDS
Need help identifying a fossil? Share clear photos, where you found it and its size with the community.
FURTHER READING
BGS Lexicon: Ben Suardal Member
Smith, Raine and Repetski: revised stratigraphy and faunas of the Durness Group (2024)
Raine: the Durness Group, including Strath Suardal and Loch Lonachan (2010)
Geological Survey: structure of Sleat and Strath, including Ben Suardal (1907)
ACCESS RIGHTS
The published locality reference lies within Strath Site of Special Scientific Interest. Its limestone pavement and associated habitats must be protected as well as the rocks and fossils. Walking access does not grant the right to extract, collect or retain fossils. Obtain permission from the appropriate landowner and mineral-rights holder, and confirm the applicable NatureScot consent requirements before sampling or taking material. Loose blocks are not an automatic exception.
Treat this as an observation and photography locality unless those arrangements have been established. Avoid damage to bedrock, limestone pavement and vegetation. Ben Suardal lies outside the mapped areas of the Skye Nature Conservation Order 2019; that does not remove its SSSI protection or the need for permission. Follow the Scottish Fossil Code.
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