News & Notices.
Page last updated 3rd May 2008
40th anniversary celebrations.
Our society is celebrating its 40 th anniversary this year and amongst the activities we have arranged is an Anniversary Show which is to be held on Saturday 20 th September 2008, at the Wesley Room, St Matthew’s Church, Clarence Street, Cheltenham, from 10 a.m. till 4 p.m. There will be activities for children as well as displays and minerals and fossils for sale, plus guided walks around Cheltenham to look at its building stone. You will all be very welcome to come along. There is no charge for the walk. We love to encourage people to notice their surroundings. The guided walk will be a taste of the book we are producing for our anniversary which will be ready for publication early next year. The book will take the form of a guide through the centre of Cheltenham explaining and examining the interesting stone used for monuments and buildings. There is an amazing variety of attractive material used in the town. It is not just Cotswold limestone and is certainly not just boring old rock!
A View of ‘ Purbeck Park’ – the Purbeck Limestone Group of Dorset
Paul Ensom, freelance museum consultant and geologist
The Purbeck Limestone Group of Dorset is a truly remarkable formation, straddling as it does the Jurassic – Cretaceous boundary, which has been variously placed within the sequence. The strata represent a range of environments originating in the hypersaline, brackish, freshwater and occasionally marine conditions which existed at different times. In addition to these aquatic environments, there were times when the sediments were exposed to sub-aerial processes. They were deposited around 140 million years ago, at a time when the ruling terrestrial vertebrates were dinosaurs, a little over half way through their 180 million year reign. Dinosaur tracks are often abundant and provide good evidence of a contemporaneous dinosaur population, more than compensating for the rarity of their actual remains. These varied environments supported an equally varied flora and fauna. A rich microflora has been recorded, the remains of macro-plants are well known, and invertebrates are at times so abundant that they become important components of the rocks. Fish remains are frequently encountered, and alongside the terrestrial dinosaurs we have evidence of diminutive amphibians, a wealth of other reptiles and the well established, but still primitive, mammals. Reptile eggshell has been found at a number of horizons. The depositional regime of the Purbeck Limestone Group provided the perfect conditions for the preservation of the abundant life and the traces they left. This talk will briefly review aspects of the Purbeck Limestone Group, drawing on the work of others, and the speaker’s research.
It is hoped to run a weekend field trip to Wales in September/October.
These will be led by Tom Cotterall ( north Wales).
Anyone who is interested in these are pleased asked to contact a member of the Committeee
The following describes a new initiative happening in the Forest of Dean which should be of interest to all persons who are interested in geology, especially within Gloucestershire.
I would like all our members to have a good look at this and wherever you can, please give your support.
When this is completed I believe it will be a major attraction to anyone interested in the subject.
Alan McKay
GEOMAP - FOREST OF DEAN
The Forest of Dean Local History Society has been awarded a grant of £107,200 by DEFRA’s Aggregates Levy Sustainability Fund administered by Natural England to produce a spectacular piece of sculpture.
Geologists are fairly certain that this is a unique project, with certainly nothing like it in the UK, and even in the world.
The Geomap will be a geology map of the Forest of Dean. Instead of bright colours on a piece of paper, the rock strata will be represented by the actual rock types, taken from both operational and disused quarries. It will be a 900 square foot rock map in surface view. It will be flat and polished, but not shiny, so that the public can walk on it.
On the map, the most important mines and quarries will be marked by discs of different colours set into the rock. The major railways and possibly some important tramways will also be marked on the map. Plaques mounted on stone will provide information about the geology and the mines and quarries shown on the map. The Geomap will demonstrate the link between the geology and the quarrying and mining industries in the Forest of Dean, and will celebrate these great industries both of the past and the present in this unique area.
Planning permission has been granted for the Geomap to be situated at New Fancy on a flat grassy area opposite the Miners Memorial which the History Society erected in 2005. An overall view of the Geomap will be obtained from the high viewpoint accessible by a footpath and there will be disabled access.
The sculptor/stonemason who will carry out the project is David Yeates, who constructed the large rock viewing points at Lydney Docks.
The idea of the Geomap evolved from discussions between David Owen of the Gloucestershire Geology Trust and the Secretary of the History Society, Dr. Liz Berry and her husband Professor David Berry. Liz and Dave then put together the grant application on behalf of the Society and they will be overseeing the ongoing work with a sub-committee with full support from the Society’s Chairman and the rest of the committee.
As partners, the Forestry Commission, Gloucestershire Geology Trust, Forest of Dean District Council and Coleford MCTI Partnership will all be offering their expertise as the project progresses.
The Geomap will be completed by March 2008. The project will be of great educational value for the local community and the wider public, as well as a unique and beautiful work of art.
The map should be like the following.
A few weeks ago I visited the project to see how far it has gone.
The following photo shows where they are at the moment.
They are about nearly halfway there as you can see. The actual rock is on the left hand side of the pattern.
If you want to keep up to date with this go to the following Web- Site.
www.forestofdeanlocalhistory.com.uk.
Latest photo news on the Geomap after its opening on 03/05/08.
Over 250 people attended the opening.
This is what it looks like. I am sure it would look far better when wet.
A noticeboard is by the Map giving all the necessary information.
A picture of the artist who made the Map, David Yeats.
For anyone interested go to David`s website
Shells and Seaweed
On April 22 nd 2006 CMGS had a field trip to Cassington Pit, near Oxford. It was well attended and plenty of interesting finds were made. I picked up a rather unspectacular piece of shale, in fact I’m not sure what made me pick it up, but on turning it over I was rather intrigued by the pattern made by some very small ‘bumps’ on the surface. As I didn’t know whether it was just ‘bumps’ or possibly some fossil trail I asked Joe Angseesing, who was also on the trip, did he know what it might be? It turned out to be bivalves. He was very interested in what seemed to be evidence that this particular bivalve attached itself to a substrate rather than being free swimming. The article below has been reprinted from the Proceedings of the Cotteswold Naturalists’ Field Club, XLIV (I), with the kind permission of the Editor. I must add that Joe wrote the article and I provided the photographs - until I asked Joe about what I’d found, I’d never heard of Bostitra buchii (Roemer).
ANCIENT SEASHELLS AND LONG-GONE SEAWEED FROM CASSINGTON, OXFORDSHIRE
Bositra buchii (Roemer) is a thin-shelled bivalve that lived in open seas in the Jurassic, more than 140 million years ago. Individual shells were probably attached to a substrate by byssus threads, in a similar manner to modern-day mussels; unlike most mussels they were attached to soft substrates above muddy sea floors (see e.g. Duff 1978). Suitable substrates were often sparse, so it might be expected that shells should be concentrated in clusters above them. It is not universally accepted that they were attached, and some authors have regarded them as probable swimmers, with clustering due to transport by currents after death (e.g. Jefferies & Minton 1965)
It is not possible to say whether the seaweed was attached to the sea floor or whether it drifted near the sea surface, but it may be concluded that the fossil assemblage was buried quickly as many individuals have their valves closed. A likely scenario is that the weed collapsed to the sea floor while at least some of the B. buchii were still alive; the community was then buried before the elastic ligament could pull the valves apart (once the shell is open the two valves lie adjacent to each other, joined at the hinge, rather than one above the other; Figure 2 suggests both modes of preservation are present).
Fig. 1.
Figure 1. The disclike structures aligned in a chain are shells of Bositra buchii. It is likely they were once joined together by mutual attachment to a piece of seaweed, now decayed. Each shell is about 1 cm. across, total width of the field of view is 30 cm. The other fossils on the slab are ammonite fragments, mainly Kosmoceras.
Fig. 2 enlarged view.
Figure 2. – close up of Fig.1. The leftmost pair of shells are a single individual with the valves opened out and joined at the hinge. In the top right shell only a single valve can be seen, as is also the case with the two shells dead centre; it is likely that these shells were buried before the ligament could pull the valves into the ‘open’ position, and that one valve was superimposed upon the other.
References
Duff, K.L. 1975. Palaeoecology of a bituminous shale: the Lower Oxford Clay of Central England. Palaeoecology 18, 443-482.
Jefferies, R.P.S. & Minton, P. 1965. The mode of life of two Jurassic species of ‘Posidonia’ (Bivalvia). Palaeontology 8, 156-185.
Ann Kent & Joe Angseesing.
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