Rosalind Jones
On the Hebridean island of Mull, on a day simply earlier than 1850, when potato famine and clearances introduced distress to the Highlands and Islands, a person (maybe accumulating shellfish to stave off hunger) ventured down right into a wind-swept gully on the Ross of Mull. Often known as Slochd an Uruisge, on the headland of Ardtun close to Bunessan, the gully opened onto a rocky cove on the mouth of Loch Scridain, with a tall sea stack made out of columns of basalt (Fig. 1).
It is a barren inhospitable place, but the wave pounded rocks made the perfect environment for limpets and winkles. Scrambling over fallen blocks on his way down to the shore, to his amazement, he saw slabs of rocks with leaves on them.
But where had they come from? There were no trees nearby. In fact, there were no trees for miles. Above the gully, on the cliff top, was heather, cotton grass and sphagnum moss. It was bog land used for peat cutting, so what on earth were these leaves doing there? They looked natural, but appeared stuck fast on the rock and were even partly covered by the mudstone. He scratched his head in disbelief. This was something to show to his landlord.
The gully was on land belonging to the young eighth Duke of Argyll, George John Douglas Campbell, who owned the Ross of Mull and the Isle of Iona. The Duke was a Liberal politician and a man with opinions on religion and science that he was fond of airing in frequent prognostications to The Oban Times, making him the butt of scornful rebuffs written anonymously to the letters page.
Aware that the Duke would be intrigued to see what he had discovered, he passed the stones with the ‘strange leaves’ on, probably at rent payment time, to ‘Factor Mor’, the Duke’s notoriously exacting steward. No one knows if the unknown discoverer of the fossil leaves was given a reward – but this is highly unlikely. The busy eight duke rarely visited his Mull estate. However, his absentee status was about to change.
Transported across the Sound of Mull to Inverary Castle, the fossils immediately excited George Campbell who, in 1851, decided to have his gully thoroughly investigated. It is very likely that the discoverer guided the Duke to the right place, as there are several gullies cut into the cliffs on Ardtun’s exposed headland and, perhaps then, he was given something for his trouble. Together with members of The Royal Society, the Duke of Argyll discovered three leaf beds, varying in thickness from 1.5 to 5.5 feet, interstratified between massive basalt lava flows and volcanic tuff. A collection of very well-preserved carbonised leaves, some of which he could clearly see belonged to the oak and the plane tree, was made.
There were other excitingly different leaves there too, such as Ginkgo, while one leaf bed consisted of compressed plant remains and horsetails. The Duke (correctly) supposed that the beds were laid down in a marsh or shallow lake in the vicinity of a volcano that later showered ash, followed by extrusions of lava upon them.
Made a Fellow of the Royal Society that same year, the Duke of Argyll decided to ask Edward Forbes FRS (who had been involved in a dredging project in 1850 around the Western Hebrides) what he thought of his collection. A very highly regarded geologist, 36-year-old Edward Forbes had just been appointed Professor of Natural History at the Royal School of Mines and he thought the leaves resembled others he had seen in Croatia.
His opinion was confirmed by Professor Heer of Zurich, who recognised the fossils as similar to some also found in Lower Miocene beds in Switzerland and also in the Auvergne. These particular fossils included conifers (Sequoia langsdorfii and Corylus grossedentate) and a plain tree (possibly, Platanus aceroides; Fig. 2). (There was also a fern, Filicites hebridica, that seems to be peculiar to Mull.) This lead Forbes to date the Ardtun leaf Beds as Miocene, the same age as the Bovey Tracey beds in Devon and Lignite beds and their associated basalts of Antrim.
George Campbell was personally very gratified to have the Ardtun Leaf Beds called ‘The Duke of Argyll’s Leaf Beds’ and gave the fossils pride of place in Inverary Castle’s collection on show for illustrious Victorian visitors. The kudos they gave him whetted his appetite to know more about the science of Geology. His reputation as an amateur scientist, as well as his position, knowledge and dialectic power, eventually made him a formidable antagonist to Charles Darwin.
When he died in 1900 (having celebrated 50 years as Duke of Argyll in 1897), his crofters on Iona and Mull’s Ross, to whom he had not been particularly kind, were all glad to see the back of the ‘old fossil’ – as many regarded him. Whether his second son, Archibald, who succeeded him, maintained the Ardtun collection, is not known, but when the ninth Duke of Argyll died in 1914, his son Niall Campbell certainly wasn’t interested in old stones. The tenth Duke of Argyll, who was Honorary Colonel of the 8th Battalion, Argyll and Sutherland Highlanders, and later Lord Lieutenant of Argyll, never married or had children, was a philistine who consigned his grandfather’s prized (and delicate) collection to a damp old shed.
The unique collection languished in an outbuilding at Inverary Castle for years until 1932, when The National Trust for Scotland was bequeathed Burg on Ardmeanach, the peninsula opposite Ardtun. Burg’s fossil tree was of a similar age to the Leaf Bed fossils and when Sir David Russell, representing the Trust visited the Geological Survey in Edinburgh to enquire about protecting what remained of the ancient conifer’s trunk from the elements, Professor Johnston of the Survey was quick to enlist the Trust’s help. (See below for links to my articles for more on this fossil tree.)
An expert palaeobotanist, Johnston knew of the involvement of The Royal Society in collecting the fossils at Ardtun and was irked to have to apply for permission to the tenth duke to examine them. The Duke was actually unwilling for anyone to see them unless they purchased them first – for £300. Professor Johnston had tried, unsuccessfully, to raise this hefty sum as he realised the collection’s geological value and was concerned for their parlous storage. Having no surplus funds, the Trust instead approached another philanthropic body, The Pilgrim Trust, describing the specimens as a collection of national importance.
Eminent men from both trusts were keen to acquire the fossils for the nation and to place them in the care of the Royal Scottish Museum, which was very keen to exhibit them. However, the canny duke kept them dangling. Possession was nine tenths of the law and he knew they were valuable, so someone could pay handsomely for them. In the end, it was the Hunterian Museum in Glasgow who purchased them – the greedy Duke no doubt laughing all the way to the bank.
Today, the Ardtun Leaf Beds is a protected SSSI. Collecting from the beds is not allowed, but visitors can look for fossils in the fallen rocks at the base of the gully. Few today are as lucky as that unknown man who found the first fossils, but this famous site is worthy of a visit for its recent history and beauty, let alone its fascinating geology, dating back around 58 million years.
To visit the Ardtun leaf beds today, take the road to Bunessan. However, before entering the main street of the village, turn right towards Ardtun, then take the first left towards Eorabus. Park on the grass at the end of the road and follow the sign-posted track to the Ardtun Leaf beds at GR377248. Descend the steep gully, which has fallen blocks at its base. (There are several gullies in the Ardtun headland and some are dangerously steep, deep and occupied by vociferous shags.)
Once you have descended into the gully with the leaf bed, with its three sedimentary layers interstratified between Tertiary lavas of the Staffa Suite, imagine that quiescent time when rivers flowed across the area into lakes where they dropped their load. They were deposited in times when Mull’s volcanoes were dormant and vegetation grew on rich, red soil of the weathered lava flows. Hebridean rain may assault you, but remember that in Tertiary times Mull’s climate was sub-tropical and balmy. Carbonised fossil tree leaves of Platanus hebridica (Plane), Corylites (Hazel), Quercus (Oak) and Ginkgo (Maidenhair) have been found. Other fossils include fruits, plant stems, conifers, ferns, insects and freshwater molluscs.
Interbedded lacustrine (lake) deposits containing silicified chalk fragments from the Cretaceous can be seen between the upper and lower lava flows. Further down the gully near sea level, the Staffa Suite columnar basalt can be examined at close quarters. A basalt filled lava tube (Fig. 3) can be seen in the cliff on the eastern side, while hexagonal and polygonal basalt columns are well displayed in these cliffs and on the adjacent sea stack.
The coastline is rugged and a small natural amphitheatre of basalt columns (Fig. 4) is tempting to explore.
However, great care should be taken in this locality, especially in rough weather. And, if you go one day, don’t be surprised to be greeted by Atlantic grey seals – you might even find a few winkles for your tea.
Further reading
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