What’s so special about South Devon?

Professor John CW Cope (National Museum of Wales, Cardiff UK) Take a trip to the South Devon coast around Easter time and you are bound to come across student parties from universities engaged in fieldwork. What is it about this area that makes it so popular as a centre for this? The simple answer lies in a single word — variety. There is probably no other area in the UK where such a wide variety of rock types and ages is well-exposed in such a small geographical compass. Let’s have a look at some of the factors. The geological succession The oldest rocks exposed in South Devon are of Devonian age and, unlike many other areas of the UK, the Devonian rocks are in marine facies virtually throughout. Looking back over the history of geology, the age of these rocks had initially proved difficult to identify and it was only after Murchison had seen the marine successions in The Rhineland and Russia that he realised that these marine rocks were the equivalent of the Old Red Sandstone farther to the north. The Devonian rocks present a variety of marine facies, with the Middle Devonian limestones being of particular note. The limestones are a local development whose presence, in an otherwise deeper water succession, is due entirely to local shallowing of the water caused by thicknesses of volcanic rocks extruded along extensional fault lines as the local basins developed. This shallowing allowed reef-building organisms to flourish and the principal ones of … Read More

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Other mass extinctions

Neal Monks (UK) The extinctions at the Cretaceous-Tertiary (K/T) boundary make up what is probably the most famous geological event in popular culture. This is the point when the great reptiles that characterise the Mesozoic went extinct. Alongside the dinosaurs, the giant marine reptiles died out too, as did the pterosaurs, and a whole host of marine invertebrates, including the ammonites and belemnites. What happened? Some geologists argue the climate changed over a period of a million years or more, thanks to the massive volcanism that created the Deccan Traps in India. Others maintain that the K/T extinctions happened suddenly, pointing to evidence of a collision between the Earth and an asteroid. Perhaps there wasn’t a single cause, but rather a variety of factors: volcanism, climate change, asteroid impact, underlying changes in flora and fauna, and perhaps even variation in the output of the Sun and resulting weather patterns. That life on Earth can be wiped out this way is the stuff of disaster movies as much as TV documentaries. However, what comes as a surprise to many people is that there wasn’t just one mass extinction at the K/T boundary, but a whole series of them that can be observed throughout the fossil record. One of them, the Permo-Triassic extinctions, appear to have been even more catastrophic than the K/T extinctions, and at least three other extinction events are comparable in scale. In between these five big extinctions were lots of smaller extinctions that aren’t well studied, but had … Read More

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Phenomenal fossil fern: Forgotten for 40 years

Stephen McLoughlin (Sweden), Benjamin Bomfleur (Sweden) and Vivi Vajda (Sweden) On some occasions, it is the hard sweat and toil of palaeontologists labouring in the field at carefully planned excavation sites that yields the prize specimen on which careers are built. On other occasions, it is the chance discovery by an amateur collector that may yield that special fossil. We present an account of one such remarkable fossil discovery by an eccentric farmer in southern Sweden. However, more remarkable is that this exceptional fossil remained unstudied and largely unnoticed in a major museum for almost 40 years, before its true significance was realised. The story begins near Lake Korsaröd, in the heart of the southern Swedish province of Scania. Gustav Andersson (born 16 May 1915; Fig. 1) owned a small homestead bordering the shores of this lake. Fig. 1. Gustav Andersson (right) at the site of the fossil wood discovery (taken some time in the 1970s). (Image: Nils Nlisson.) Although Gustav made a living from farming, his true passion was natural history and he even adorned the walls of his house with his own sketches of Mesozoic scenes. Although he never received any formal scientific training, Gustav was an avid reader and had a keen eye for nature. He used these skills to identify a great range of plants on his property down to the rare ground orchids that episodically bloomed on the local volcanic soils. He also identified Neolithic burial sites, flints, stone clubs and other ancient human artefacts … Read More

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Geology of the Moray Coast

Dr Sue Beardmore (UK) When most people think of Scotland, the images that come to mind are those of high, heather covered mountains like Ben Nevis, islands like Skye, Arran or Rum, or the endless rugged coastline of the northwest coast. However, there is another half to the country, along the east coast, which few people have explored. For example, the county of Moray offers Burghead Bay, where pill boxes sit half submerged in sand, or there are the frequently climbed sea cliffs below Cummingston and Covesea, and Findhorn Bay, the only natural harbour on the south side of the Moray Firth, where shipwrecks litter the beaches at low tide alongside remnants of an old settlement destroyed by shifting channels. Fig. 1. Baryte mineralisation in Permian sandstone at Hopeman.In terms of geology, the Moray shore provides evidence of the ancient landscape 250mya, easily found by following the coastal path, a walkable distance east from the village of Hopeman. A short detour onto the beach, behind the brightly coloured huts, reaches small outcrops of Permian sandstone, the Hopeman Sandstone Formation, which occurs continuously along the coast for several kilometres. At this particular spot, the sandstone is heavily mineralised with barytes, primarily as cement holding the medium-sized grains in place, but also as concentrations a few centimetres across that give the outcrop an overall speckled appearance and nearly obliterate the original bedding (Fig. 1). Such an outcrop can also be found near Covesea Lighthouse, as can fluorite in characteristic (but difficult to … Read More

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Can the end-Permian mass extinction be attributed to a single, catastrophic event?

Robert Broughton (UK) The end Permian mass extinction occurred 251mya and marked the end of the Palaeozoic era. The loss of life is currently estimated to consist of 95% of the marine fauna and around 70 to 77% of the known terrestrial fauna (where the fossil record is inevitably less complete). This article will provide an overview of the many events and processes that played a part and a discussion whether they can all be attributed to a single, root cause. Reef evidence At this time, the landmass was united into the single, super-continent of Pangea, surrounded by warm shallow seas with abundant reef systems. This extensive reef fauna supported a variety of suspension feeders (for example, crinoids, rugose and tabulate corals, and so on), which were the most heavily hit by the extinction event, with all the known corals dying out. Modern scleractinian corals only appeared in the Triassic and there is a considerable gap in the coral fossil record at this time. Other reef inhabitants, such as the last phillipsid trilobites also became extinct. All these creatures were sessile or relatively immobile inhabitants of the reefs that occupied a relatively narrow zone on the continental shelf. This habitat must have been destroyed almost globally by a number of factors, but importantly, the single shelf margin around Pangea meant there was no other shallow reef environment for the fauna to migrate to. Fig. 1. Reef evidence. Tectonic activity The single continent of Pangea was always doomed to split apart. … Read More

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