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Fossil Fish of Caithness

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Fossil Fish of Caithness The Story Begins… Ancient Geography Achanarras Quarry Site of Special The Lake Environment Preservation of the Fish Scientific Interest (SSSI) Imagine an ancient tropical lake so deep and dark Scotland has not always looked like it does today. Achanarras Quarry was once part of Lake Orcadie Lake Orcadie expanded and contracted as the The fish are preserved in that the bottom had no oxygen or much life of any 400 million years ago it was south of the equator and there, in what is known as the fish bed, you can Middle Devonian climate varied. At times of low flagstones of the fish bed. The sort. Most living things had to live in the shallows and part of a huge mountain range, higher than the find more species of Old Red Sandstone fossil fish water supply, when the climate was warm and dry, it detail of preservation is such that where the unpredictable climate made them Alps, that stretched from North America to Norway. than anywhere else in Scotland. These include was reduced to a salty inland desert drainage basin. delicate fin structures and even vulnerable to storms and changes in temperature or The mountains were formed when ancient oceans fossils of armour-plated fish, the ancestors of However during wetter and probably cooler periods, skin outlines are seen in the best salt levels. In this fragile home fish suffered were destroyed and continents collided together. species we see in the fishmonger’s today. The the lake filled and overflowed, allowing fish to migrate specimens. The fish carcasses occasional mass deaths and their dead bodies Millions of years of erosion gradually wore down the armour plating offered some protection from larger into it from the sea. The fish bed was deposited were gently covered by sediment floated out and sank into the mud at the bottom of high peaks and powerful rivers washed the sand predators, whose fossils can also be found. when the lake was full, and the water tens of metres and gradually buried and during the lake. 4000 years went by, 2 metres of mud and and mud into lakes. In the lakes it settled in layers Achanarras Quarry SSSI is renowned all over the deep. Fine layers in the bed record a seasonal this phase the internal structure fish bodies accumulated……and there the fish lay, and helped preserve the remains of plants and world for its well preserved fish of the Middle climate as the sediment was being deposited over of most of the fish decayed. perfectly preserved and undisturbed for the next animals. This is what happened at Lake Orcadie Devonian age (385 million years ago) and is some 4,000 years. The fish mainly lived in the shallow Further burial squashed the fish 385 million years. and other similar lakes that existed in the area that managed by Scottish Natural Heritage (SNH). oxygen rich water of the lake margins and mass flat and the lake mud was now lies between Shetland and Inverness. deaths might have been caused by algal blooms (a converted to solid rock. Many Now step forwards through time. rapid increase in the population of simple plants) millions of years later the rocks The dinosaurs came and went. removing oxygen from the water, storm activity, and were uplifted, eroded and finally Lake Orcadie where the fish used the water getting too hot or salty. All these quarried to reveal the fish bed. to live is long gone. But the processes cause fish mortality events even today. Dipterus amazing fossilised fish are still here in the Caithness Flagstone. They were discovered when Achanarras Quarry was first worked for flagstones and roofing slates in the 1870s and their story helps us understand evolution and the geological formation of Scotland. Coccosteus Pterichthyodes Directions to the Quarry Industrial history of Achanarras Modern Achanarras Other Fossil Sites in The Scottish Fossil Code Fossil Fish On travelling North up the Quarry SSSI Caithness A9 towards Thurso turn of Caithness left on to the B870 at Mybster. This turning is THE 385 MILLION YEAR OLD STORY The Achanarras Now, parts of the tips are turned over regularly Fossils can be found at many other sites in At Achanarras Quarry, just before you reach the OF ACHANARRAS QUARRY village of Spittal. On the Quarry started as using a mechanical excavator. This action provides Caithness. These often contain fish beds of the Scottish Fossil Code B870 take the first turning a small farm more material for collectors to search for fossils, and different ages from that at Achanarras. By has replaced the fossil on the right (about 1km quarry in 1870. ensures that this internationally important locality comparing the species found at each site the history collecting permit system west of the Mybster junction beside a forestry Later it was does not become of Lake Orcadie, and which fish species lived at that was previously in operation there. Searching plantation). Both of these worked by the overgrown. These particular times, can be revealed. Most of the other for and collecting fossils is permitted subject to turnings are marked with Thurso Flagstone activities have sites are on private land where you will need the visitors following the Fossil Code. You can brown tourist signs for Quarry, and by resulted in several owner’s permission to collect fossils. The most download a copy of the Scottish Fossil Code from ‘Achanarras Quarry’. 1891 the fish bed was exposed. The quarry fell into new species being important areas are also protected as Sites of the SNH website (www.snh.org.uk/fossilcode/). th This track will take you to disuse in the early 20 Century, but was worked for found and Special Scientific Interest (SSSIs). There is the Please read the information about fossil collection at the quarry car park. Once at the car park, there is a panel roofing slates in 1959-61. In the early 1970s there described. opportunity to see some preserved fossils at the Achanarras Quarry SSSI on arrival to the car park. with a map indicating where the quarry is located. was minor quarrying activity. Wheeled wagons on Digger turning over quarry material Caithness Horizons Please shut any gates you open behind you as you walk to rails, called bogies, were used to take the waste The facilities at Achanarras were upgraded in 2008. museum in Thurso. Scottish Outdoor Access Code the quarry. from the quarry to the outer tip. During working the You can now discover more about the fish, walk a Further Information The Scottish Outdoor Access Code Please note that there are no toilet facilities at the site. water was drained from the quarry by means of a geological ‘timeline’, search for fossils, find out what For further information on local applies to all land in Scotland. The access siphon. It took about 10 days to empty. The last has been happening in the fossil world and record geology and fossils see track to Achanarras Quarry is through time it was drained was in 1980 for a scientific your finds at Achanarras. Excursion guide to the private land and the Access Code should study of fossil distribution through the fish bed. Geology of East Sutherland therefore be followed at all times. Please Achanarras Quarry is also located in a and Caithness. N H Trewin and A Hurst (eds) Dunedin read the safety notice on arrival to the For the next 20 years collectors scoured the tips for wild area with interesting plants Academic Press. 2009 quarry car park. Contact details fossils and it became increasingly difficult to find and animals. Watch out For imaginative time-travel stories of excursions to famous Please let SNH know if any rare or particularly fine fossils new specimens. for frogs by the quarry Scottish fossil localities (including Caithness fish, and the are found. pool in the early spring, and Jurassic of Helmsdale and Skye) see Fossils Alive! by N H Trewin (Dunedin Academic Press, 2008) Scottish Natural Heritage nesting birds such as North Highland Area Office oystercatcher, curlew, lapwing and skylark. You may For more information on the geology and landscape of The Links, Golspie Business Park, Golspie, KW10 6UB even be lucky Scotland please visit the SNH website to view the online T: 01408 634063 E: [email protected] publication: Scotland: The Creation of its Natural Landscape, enough to spot a www.snh.org.uk and other regional publications in the series A Landscape hen harrier Fashioned by Geology. © Scottish Natural Heritage 2009 hunting over the heather moorland. Acknowledgements Majority of text, photographs and sketches by Professor Nigel H. Trewin, University of Aberdeen. Bogie used to carry quarry waste A Guide to Achanarras Fossils Armoured Fish - the Placoderms Spiny-finned fish, the Acanthodians Fish fins Coccosteus, Rhamphodopsis, Homosteus, Actinolepis and Pterichthyodes are representatives of Various species of Diplacanthus, Cheiracanthus and Mesacanthus occur at Achanarras. They the extinct group of armoured placoderm fish. The head and part of the body is covered with bony are all characterised by spines supporting the fins, and a covering of tiny scales. They are plates. All except Pterichthyodes lacked scales on the rest of the body, so internal features can be frequently poorly preserved with a tendency for the head to be fragmented. seen in fossil specimens. DORSAL Mesacanthus Coccosteus Homosteus This small fish is common In this common 30cm long A large fish with and is seldom larger than Achanarras fish, the head and an armoured body 5cm. Several may be part of the body are covered in up to 40cm long. found on a single slab of rock. It was probably a shoal fish feeding on bony plates with an ornament of The tail has not microorganisms (tiny, microscopic plants and animals) in the lake water.
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