OUGS East Anglian Branch Newsletter Summer 2019
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OUGS East Anglian Branch Newsletter Summer 2019 From the Branch Organiser Dear All, Welcome to another branch newsletter. I hope everyone has had a chance to read about our forthcoming Symposium in the main OUGS Newsletter. As you will have realised this is a ‘special’ at the instigation of the OU to celebrate their 50th Anniversary. Fewer field trips but more to explore at the OU itself, including lab tours, workshops and demonstrations, with OU staff speaking about their latest research. There is still time to book this - see the OUGS website for details and booking form. Since the last newsletter I have attended both the AGM (including the OUGS Committee meeting) and the Branch Organisers’ meeting. At both, the future direction of the OUGS was discussed. Given ever falling membership numbers various ways forward have been proposed. Closer liaison with the OU is now on the cards, as exemplified by our forthcoming Symposium, which may help stabilize numbers. Should we consider smaller area groupings, with regional coordinators, perhaps based on area geology? Another area of discussion was the annual Symposium which is proving ever more expensive to run. Perhaps this ought to be a biannual event, with the AGM having a bigger profile. We discussed some of this at our last branch AGM and I would like to hear your further views on the subject. More immediately, as a branch we need more suggestions of activities for our events co- ordinator to follow up. As I think I’ve pointed out before our branch covers a wide area and I’m sure there are geological gems yet to be explored. Don’t be shy of contacting any committee member with your wish list. Phil Ridley ________________________________________________________________________ On the beach at Walton-on-the-Naze, amongst the mountains of the Apennines and near the bank of the Yangtze River. (by Philip Findlay) Fig.1 Pyritised twig with knot Fig.2 Pyritised twigs When I visit Walton-on-the-Naze, I always enjoy looking closely at pieces of the pyritised wood that can be found on the beach (Figs. 1 and 2). The recognisable, intricate details that remain intact on the surface of these fossils are both amazing and familiar, and, although I have heard it many times before, I am still surprised by the metallic clink produced when two of the fossils are gently tapped together. Erosion by the sea has set free the pieces of pyritised wood from the bed of blue-grey London Clay that is exposed in the cliff and along the beach. Geologists calculate that the London Clay and its fossils are between 57 and 52 million years old, dating from the Eocene epoch, although only the oldest strata now remain at the Naze. The pieces of wood, along with lots of sediment, were carried down by rivers to a sea where the waterlogged wood sank and the sediment settled, burying the wood and the process of fossilisation of the wood began. Above the London Clay on the southern section of the Walton cliffs are the reddish-brown, coarse-grained, shelly sands of the Red Crag Formation. The Red Crag is much younger than the London Clay, just 2.4 million years old, from the early Pleistocene epoch. The boundary, the unconformity between the London Clay below and the Red Crag above, can be seen in the cliff, although in places it is obscured following collapses and slumping. (Fig.3). Fig.3 Collapses of the cliff Further to the north the Red Crag has been completely eroded and the London Clay is overlain instead by thick deposits of Loess (Brickearth), fine silt deposited as wind- blown dust during the last (Devensian) glaciation (Fig. 4) Fig.4 Devensian Loess above, London Clay below The pyritised wood fossils used to be collected as an industrial ore from the beach at Walton and from other beaches in South-east England where the London Clay was similarly exposed to erosion by the sea. Their high iron sulphide (FeS2) content (Fig. 5), made the pyritised wood fossils the key raw material for a process that produced crystals of ferrous sulphate heptahydrate, FeSO4.7H2O. In the past, this compound was commonly known as green vitriol or copperas and so the pyritised wood fossils and other lumps of iron pyrites became known as copperas stones. Fig. 5 Fresh, broken surface of pyritised wood showing the metallic lustre of the iron sulphide Green vitriol was used as a dye fixative, a mordant, in the dyeing of wool. It was also used to make inks and dyes, especially for dyeing leather. In Europe, by the middle of the sixteenth century, the use of copperas stones for producing green vitriol was well- established. George Bauer, a German mineralogist writing under the name Georgius Agricola, described several different processes used to produce green vitriol in De re metallica, published in 1556. The fourth of these different processes involved producing green vitriol from vitriolous earth or stones, “ex terris aut lapidibus atramento”. i Lou Henry Hoover and her husband Herbert Hoover completed the translation of the original De re metallica from Latin into English in 1912. In one of their footnotes they explain: “The term for vitriol used by the Roman authors, followed by Agricola, is atromentum sutorium, literally shoemaker’s blacking, the term no doubt arising from its ancient (and modern) use for blackening leather”.ii (Later, in 1929, Herbert Hoover became the 31st President of the United States.) Fig. 6 shows a woodcut from De re metallica, illustrating some of the final stages described in the production of green vitriol from copperas stones.iii For more than a year, the copperas stones were first exposed to the weather and then immersed in water. The resulting liquid (a mixture of ferrous sulphate and sulphuric acid as well as water) was heated to remove excess water and then iron strips were added to produce even more green vitriol (the added iron reacting with the sulphuric acid). The woodcut shows: a lead cauldron (A) where excess water is removed, moulds (B), and on the ground by the pourer’s right foot, the “cakes” of green vitriol (C). Fig. 6. Production of Green Vitriol in 1556 By the end of the sixteenth century, centres of the copperas industry were also active in England: Lambarde, for example, is reported to have noted in A Perambulation of Kent in 1579, that at Queensborough Castle on the Isle of Sheppey, there was the production of copperas - “out of a certein stone that is gathered in great plenty upon the shoare”. iv The County of Essex, as well as supplying copperas stones for its own processing centres, also shipped the ore to other centres such as the one at Queensborough on the Isle of Sheppey and to centres nearer London, such as at Deptford. v The first people paid to collect the copperas stones from the beaches would have recognised on the surface of the pyritised wood the same sort of intricate details as we can see today, and, similarly, this recognition may have prompted thoughts and ideas about the nature and the origin of these objects clearly displaying such familiar features. Unless the collectors were able to write down their reflections for circulation or had a public platform to share their thoughts with others, then their ideas fed only their own imaginations. This was over two centuries before James Hutton, in 1785, at a meeting of the Royal Society of Edinburgh, first publicly stated what the conclusions his own studies and observations had led him to and which he later summarised as: “….we may look for the transactions of time past, in the present state of things upon the surface of this earth, and read the operations of an ancient date in those which are daily transacted under our eye”.vi Leonardo da Vinci (1452-1519) had observed and registered familiar details on the individual shells making up the shell beds he found embedded in rocks in the Apennine Mountains and he did write down his associated thoughts. The arguments that the shells had been left there after the Great Flood described in the Bible or that the shells had formed within the rock did not convince him.vii In a journal that he wrote between 1504 and 1510, now known as the Codex Leicester, he recorded what he saw as a past community of living shells: small and large shells, some with only a few and some with many growth rings. He wrote about the holes he saw in the shells, details that matched the borings suffered by living shells, and in doing so he set down perhaps some of the earliest records of trace fossils.viii His thoughts about the nature of those shells assumed their origin as living creatures that fed and grew in the sea, that were then buried in sediment at the bottom of the sea before the area later became land. He did not publish or circulate these writings during his lifetime so his explanations were not available to others until much later. His writings preceded the talk, mentioned above, given by Hutton at the University of Edinburgh, by more than two hundred and fifty years; however, similar ideas had already been written about and published more than four hundred years before da Vinci had written even the first word of his own journal. Shen Kuo 沈括 (1031–1095) lived in China during the Song Dynasty. In 1088, when he retired to his home near the Yangtze River at Zhenjiang, he wrote Meng xi bitan, 梦溪笔谈 often referred to in English as Dream Pool Essays.