Trotternish, Skye: Summit to sea since the Jurassic

Trotternish contains many dinosaur remains and other fossils, giant rock steps made of lavas and the largest continuous area of landslides in the British Isles

Trotternish landscape. Image: John Gordon.

Jurassic rocks and fossils
The oldest rocks on the Trotternish Peninsula are 190-150 million years old, and were laid down in the waters and on the shores of relatively shallow and warm seas during the Jurassic period. These shallow seas were very different to the waters of the North Atlantic that erode Skye’s shores today. Many stunning fossils occur in the Jurassic marine sedimentary rocks (clays, siltstones, sandstones and limestones), where ammonites, belemnites, brachiopods and bivalves abound. Two beds contain thousands of small round and pentagonal ‘counters’ (ossicles) that made up the flexible stalks of crinoids (sea-lilies). Marine reptiles (ichthyosaurs and pleisosaurs) and fish also cruised these waters as top predators.

The Jurassic sediments of the Great Estuarine Group record terrestrial ecosystems, including plants, insects, early mammals and, yes, dinosaurs. Multiple trackways of dinosaur handprints and footprints have been found. Numerous species are represented, including carnivorous theropods (early cousins of T. rex), long-necked sauropods (relatives of Brontosaurus weighing around 10-15 tons and measuring 15-20 metres long), and beaked and plate-backed plant-eaters. Extensive sauropod trackways are accessible on the tidal platform near Duntulm Castle. The best-preserved theropod tracks are near the Staffin Slipway. New discoveries are still made on Scotland’s ‘Dinosaur Isle’, and many fossils are on display in the Staffin Ecomuseum.

Lava stacks
Massive rock steps run the length of the Trotternish Peninsula, on top of the Jurassic rocks. This stack of rocks, which has been estimated to be about 1.5 km thick, represents a pile of lavas generated as the North Atlantic opened around 55 million years ago. A wide range of volcanic rock types can be seen with interbedded sediments. Many of the igneous features on the eastern coast are examples of sills, with column-like joints – Kilt Rock is a famous example.

Landslides
The Trotternish escarpment, with its masses of lava blocks and strange rocky pinnacles looming through swirling mist, may appear as ‘a nightmare of nature’ as it did to Alexander Smith writing in 1865. This wild landscape includes two spectacular groups of postglacial landslides at the Storr and Quiraing. Huge blocks of lava have slipped along weaknesses in the underlying Jurassic rocks, with other blocks toppling into the gaps left behind. The inner zone of the landslides is a labyrinth of tilted lava blocks, weathered pinnacles, buttresses and fantastic rock architecture. Weathering has carved the famous Old Man of Storr from a block detached from the soaring cliffs of The Storr. At Quiraing, John Arnott MacCulloch wrote in 1905 that ‘great slices of rock, fissured and cracked, stand apart from the main precipice behind …… These detached masses and the many airy pinnacles of every conceivable form have the most weird and fantastic appearance, especially if wisps of summer mist glide through and among them’. Local names for various landform features highlight their individual characteristics: the ‘Needle Rock’ and the ‘Old Man’ at Storr, and the ‘Needle’, the ‘Prison’ and the ‘Table’ at Quiraing. The outer zone of the landslides consists of older, subdued landforms that were modified by the last Scottish ice sheet (around 35,000-15,000 years ago).

Text contributed by Al McGowan, John Gordon, Steve Brusatte & Neil Clark

Find out more
Visit Staffin Museum: http://borve.net/staffin-museum.co.uk/
https://depositsmag.com/2016/08/02/dinosaurs-in-scotland/
Landscape Fashioned by Geology book: https://www.scottishgeology.com/find-out-more/publications/#skye
https://docslide.net/education/the-trotternish-landslides.html
Ballantyne, C.K. (2016). Rock-slope failures on Skye. In: Ballantyne, C.K. & Lowe, J.J. (Eds), The Quaternary of Skye. Field Guide. Quaternary Research Association, Cambridge, pp. 77-88.

Duntulm platform, easily accessible site with numerous trackways. Image: Stephen Brusatte.

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