Tag: clay

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Clarkia Flora: 16-million-year-old plants offer a window into the past

Margret Steinthorsdottir and Helen K Coxall (Sweden) Near the small town of Clarkia in Shoshone County, Idaho in the USA, exists a rich and unique fossil deposit. The Clarkia fossils, or Clarkia Flora, as the deposit is mostly called due to the abundance of fossil plants, is so well preserved that the assemblage is referred to as a “lagerstätte”, a scientific term reserved for the world’s very finest fossil deposits. The Clarkia fossils are found in sediments that are now known to be about 16 million years old and belong to a period in Earth history called the Miocene. By this time, the (non-avian) dinosaurs were long extinct (the last of these dinosaurs disappeared about 66 million years ago), the Earth’s continents were more or less in the same position as today, and many of the animals and plants would have started looking familiar to modern humans (who emerged much later, about 200,000 years ago). Fig. 1. The entrance to the “Fossil Bowl” motocross racetrack and fossil locality near Clarkia, Idaho. Among the Clarkia fossils can be found various insects, fish and occasionally the remains of small mammals. However, most striking is the wealth of plant fossils in the form of exceptionally well-preserved leaves, nuts, seeds and wood. Impressively, one can find leaves of oak, laurel, pine and birch that look virtually identical to those we find today. If you look quickly when a new fossil is newly exposed from within the host sediments, you may occasionally even see the … Read More

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Fulletby brickyard: A classic locality in the Upper Jurassic Kimmeridge Clay of Lincolnshire

John P Green (UK) The Upper Jurassic Kimmeridge Clay Formation in Lincolnshire crops out along the western edge of the Lincolnshire Wolds scarp (Swinnerton and Kent, 1981) and many years ago was formerly exposed in many small workings that exploited the Lower and Upper Kimmeridge Clay Formation for brickmaking. The once famous brick pits at Market Rasen (TF120888) and at Stickney near Boston (TF342570), both richly fossiliferous and the source of many historic museum specimens (in particular, ammonites and marine reptiles) have long since closed and the sections are no longer accessible. Fig. 1. Saurian vertebra (crocodilian or possible plesiosaur), discovered on the reverse of a Pectinatites ammonite. Nevertheless, I have located another former, now largely overgrown brickyard, near the village of Fulletby (TF298734), situated just under five kilometres north of Horncastle. Whilst largely overgrown, small exposures remain of the Upper Jurassic Kimmeridge Clay Formation. The Palaeontographical Society lists the locality of Fulletby brickyard in its 1954 publication, Directory of British Fossiliferous Localities. It identifies the exposures present as belonging to the ammonite zone of Pectinatites wheatleyensis, and it was indeed thanks to this publication that I was able to discover this locality. The locality is also briefly discussed in Swinnerton and Kent (1981). The exposures that remain are intermittent and scattered, but shallow excavations made by me have revealed a sequence of richly fossiliferous mudrocks, which has allowed a rare opportunity to inspect and collect specimens from this rarely exposed horizon at this little known geological locality in Lincolnshire. … Read More

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Saltwick Bay, North Yorkshire

Emily Swaby (UK) Saltwick Bay is located along the Yorkshire Coast, between Whitby and Robin Hood’s Bay, and can be accessed from the Cleveland Way, which passes the spectacular Whitby Abbey. The geology of the area is predominantly Jurassic in age, with the site often being described as a ‘fossil treasure trove’. The bay yields a wide variety of specimens, including common ammonites and belemnites to rarer finds such as marine reptiles, Whitby Jet and even dinosaur footprints. Even though Saltwick Bay is close to Whitby, it is still a very productive locality and you never leave empty handed. In fact, it is a good location for families and beginners. The walk to Saltwick Bay from Whitby itself is approximately 2.4km and provides many picturesque views of the abbey, the harbour entrance and the remarkable coastline. The steps leading down to the beach are located just past Whitby Holiday Park, but can sometimes be slippery during winter months. It is also recommended that you check tide times for the area before arriving, as high tide can limit the extent of accessibility and could potentially cut you off. Fig. 1. The steps descending down the cliff to the bay. Once you have made your way down the steps, fossils can be found immediately among the scree or in the shingle. However, it is advisable stay away from the base of the cliffs, as rock falls are common, with loose fragments of shale constantly falling down. Fig. 2. The Nab is a … Read More

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Trouble with pyrite

 Fred Clouter (UK) On Wednesday, 26 April 1882, the Queenborough Chemical and Copperas Works were auctioned off, heralding the demise of the copperas industry on the Isle of Sheppey. Green copperas was used to make sulphuric acid or vitriol, chemical manures and dye stuffs. Being in Queenborough Castle in the year 1579 I found there one Mathias Falconer, A Brabander, who did in a furnace that he had erected there, trie to drawe very goode brimstone and copperas oute of a certain stone that is gathered in great plenty upon the shoure near untoe Minster on the isle”. This extract is from ‘Lambard’s Perambulations of Kent’ and is probably the earliest known reference to a ‘chemical’ factory in Britain. Fig 1. Poster advertising the sale of Queenborough Chemical and Copperas Company. The first reference that I have that links copperas with the collection of fossils is found in the ‘Life and letters of Edward Lhwyd (second Keeper of the MUSEUM ASHMOLEANUM) Oxford March 28th. 1695’. Below is an excerpt from ‘A Museum of the Early seventeenth Century’ By Cyril Edward Nowill Bromhead, BA, FGS, FRGS. (Read 18Th. June, 1947) referring to the Lhwyd letter: If you could setle a correspondent in the Isle of Shepey to save us all the Crampstones the copras-women pick up for a month or two, I would now fall about a Lithologia Britannica: and so contrive it that the first tome shall consist of onely teeth and bones of fish.” (Sharks’ teeth were called ‘cramp … Read More

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Fulgurites: With the look and shape of lightning bolts

Deborah Painter (USA) If the characteristics referred to in the title were their only quality, fulgurites would be fascinating. However, they have other unusual qualities that make them even more amazing. For example, some hold ancient air within that can offer a window into palaeo-environments. Fulgurites are natural tubes or, in the case of rock fulgurites, crusts of glass formed by the fusion of silica (quartz) from a lightning strike. They are categorised in four main types: clay, sand, caliche and rock fulgurites. In the case of the sand or clay fulgurites, the shape mimics the path of the lightning bolt as it enters the ground. All lightning strikes hitting the ground are capable of forming fulgurites, but not all lightning strikes will do so. A temperature of 1,800oC is required to melt sand and form a fulgurite, but this is not usually an impediment, since most lightning strikes have a temperature of 2,500oC. Fig. 1. North Carolina’s sand dunes are a popular place to find sand fulgurites. (Photo by D M Maxos.) In addition to the four main types mentioned above, there are the droplet fulgurites, which obviously resemble droplets, but, in composition, are similar to the clay and caliche fulgurites. Sand fulgurites tend to have rather fragile glass walls. Rock fulgurites are found not as discrete structures, but as veins or branching channels on a rock surface, or as a lining of fractures, which existed before the lightning strike. Fig. 2. A large (9cm) specimen. (Photo by Mark … Read More

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