Wessex Branch Newsletter
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The Open University Geological Society Wessex Branch Newsletter Website http://ougs.org/wessex July 2017 CONTENTS Branch Organiser’s Letter Branch Organiser’s Letter Page 1 Hello All, The Etches Collection, 22 Jan 2017 Pages 2-4 Studland, 7 May 2017 Pages 5-7 Although summer is now supposed to be in full swing, it occurred to me that we might all need Minerals guide no. 25 – Silver Page 7 reminding about it. It is still the best time to Weymouth Bay, 23 April 2017 Pages 8-9 Dorset Building Stone Page 9 get out and about, enjoying our countryside and looking at the rocks. The membership Other organisations’ events Page 10 figures given out at the AGM showed that all Forthcoming Wessex Branch events Page 11 branches have suffered a decrease in OUGS events listing Page 12 membership, so there are fewer of us doing it. Wessex Branch committee Page 12 This isn't a new thing, the trend has been there for years now. This isn't a massive problem for our branch yet, but it is an issue we need to be aware of. We need new members. The number of new OU geology students is still decreasing. It also seems that word of the OUGS is not reaching some of the new OU students. As a branch, we are trying to be proactive and visiting schools and U3A groups. I'll keep you informed of our progress. In the This fossil ichthyosaur, with a full belly, was one of the meantime, if you can remember to tell people many amazing specimens seen on the branch trip to about who we are and what we do, it could The Etches Collection in January (report on pages 2-4). Photo by Jo Southall, JBOT benefit us all. The Charnwood trip on the 3rd and 4th June On 24th September we are very lucky because was very successful. What little rain there was Sam Scriven has kindly agreed to lead another arrived just as we were winding up the trip. trip to Lyme Regis with an emphasis on fossiling. Having last seen this area in 2006, it was Sam was a geologist at the Charmouth Heritage interesting to realise just how much I had Coast Centre for four years. The experience he forgotten about it since then. Seeing gained there in geological interpretation led him unmetamorphosed Precambrian deposits and on to his present position of Earth Science fossils is amazing. Our thanks go to Mark for Adviser for the Jurassic Coast. organising that one. You may have noticed that the trip to Jersey (3rd th On the 16th of July we have a trip to to 6 October) is now full, with a waiting list. Worbarrow with Jeremy where he will show us People do drop out, though, for various reasons the Cretaceous succession through its various so if you want your name on the waiting list - climate and sea level changes between the with no promises - get in touch. Portland Stone and the Chalk. Be advised that The OUGS Symposium is at Edinburgh (Queen this date has changed since it was first Margaret University) in August this year. I hope advertised. As with Charnwood, there is always to see some of you there. something new to see and learn at Worbarrow no matter how many times you've been there Best Wishes before. Although it will interest us all, it should Colin Morley, Branch Organiser Wessex be of particular interest to OU students studying E-mail: [email protected] environmental science. Wessex Footnotes July 2017 Page 1 WESSEX OUGS FIELD TRIP TO THE ETCHES COLLECTION AND KIMMERIDGE BAY, DORSET, SUNDAY 22 JANUARY 2017 Leader: Steve Etches MBE Report by Chris Hawkes Following a day of fascinating lectures on the Cretaceous at the Wessex AGM, on the Sunday we headed for Kimmeridge to go further back in time to the late Jurassic seas. Led by Steve Etches himself, we would see the fossils of the Etches Collection in the morning, and the cliffs and ledges of Kimmeridge Bay in the afternoon. It was a real privilege to be led throughout the day by such a knowledgeable and engaging guide. Steve Etches has been collecting, preparing and preserving fossils from the Kimmeridge clays and shales since he moved to the area in the 1980s. For years, Steve’s ever-burgeoning and unrivalled collection was famously housed in his garage but in October 2016 - with collaboration from many people, organisations and Lottery Funding - the Etches Collection building was opened to visitors and Steve’s dream of being able to share his collection became reality1. The building’s modern lines blend sympathetically with the older village buildings and inside it provides light, airy and flexible accommodation. Steve explained that the building is multi- The entrance to the building Photo by Jo Southall, JBOT purpose. As well as providing a permanent home for the fossil collection, the lofty Clore Room provides a new all-mod-cons village hall and there is a smaller meeting room available. The building is “green” and energy efficient, heated from a geothermal borehole 800 metres deep. It is also very accessible for wheelchair users, as Jo Southall describes in her blog2. For more details of the architecture and building stones see Helen Phythian’s report in the December 2016 issue of Footnotes3. The Rocks at Kimmeridge The Kimmeridge Clay Formation consists of bands of mudstones, oil shale and dolomitised limestones which were deposited around 150 Ma in a restricted basin. These relatively shallow warm seas supported a rich marine fauna including ammonites, reptiles and ancient fish. The remains of these animals have been preserved in the sea-floor mudstones, providing the fossil-rich rocks we see today. Steve explained how compression during diagenesis has caused most Kimmeridgian fossil specimens to be extremely flattened. The best and most complete specimens tend to come from the harder limestone beds. Preservation is encouraged by The cliffs at Kimmeridge, looking east from anoxic conditions and some of the best specimens Washing Ledge Photo by Chris Hawkes are partially pyritised, which means they must be stored in controlled conditions to prevent decay. The Formation is extremely economically important. It extends across much of northern Europe and is the main source for North Sea Oil. The Kimmeridge Clay is thus one of the most intensely studied hydrocarbon source rocks, but there has been less attention given to its fossil history. Steve is doing much to redress the balance. Several of Steve’s discoveries, like Darwin’s ‘missing barnacle’ (fittingly named Etcheslepas durotrigensis) have led to new insights in evolutionary theory and knowledge about the Ammonite eggs - the Kimmeridgian marine ecosystem. He hopes that planned CT scanning of first discovery. Two recently discovered rare ammonite egg sacs will yield new insights into how clutches of eggs laid in little strings. ammonites reproduced. Photo by Chris Hawkes Wessex Footnotes July 2017 Page 2 The Gallery: the fossil exhibition The Gallery is a single lofty room, suffused in blue light from the ever-moving waters of the late Cretaceous virtual ocean that illuminates the room from above. Ammonites and massive predators swim in this watery environment. At one end of the gallery, behind a glass wall, is a workshop for specimen preparation, and beyond that, not on display, the rest of the collection is stored. Steve has concentrated his fossil hunting on the local coast, so all the fossils displayed are Kimmeridgian. He is passionate about what the fossils reveal about how the creatures lived and interacted with others. Thus, rather than A virtual ammonite being organised taxonomically, the display cases use some of Steve’s best Photo by Jo Southall, JBOT specimens to illustrate the responses of the Kimmeridgian fauna to evolutionary pressures. The fossils are complemented by hand drawn explanations and illustrations which look like pages from a fossil collector’s log book. The descriptions below give just an impression of some of the material on display – best to visit yourself or look at the website4 to see the full variety and quality of the fossils on display. The website also includes an illustrated database of over 2,000 specimens in the collection. Adapt and Evolve For me, the most stunning specimen here is a wonderfully preserved ichthyosaur skeleton. Steve explained how the features of this reptile were adapted to its role as a predator: large orbits allowed large eyes, whilst the finely pointed sharp teeth allowed it to grasp its squid- like prey. But the display also includes remains of the primitive fish coelacanth, an impressive plesiosaur, shark remains, a marine crocodile, an illustrated timeline of the evolution of Kimmeridgian ammonites, and the discovery of the “missing link” goose barnacle which Darwin speculated on in the 19th century. Ichthyosaur skeleton Photo by Chris Hawkes Eat or be Eaten This display focuses on the features of the carnivores in the food chain, showing the features that allow them to be effective predators. In the centre of the room, we clustered round a 2 metre long pliosaur jaw, collected over time by Steve as it gradually eroded and fell from the cliffs. Steve explained how the form of the teeth and jaw showed this was an apex predator. In the wall display, the still-full belly of a juvenile ichthyosaur reveals that it fed on fish, squid and other marine organisms [see photo on front page]. Steve also explained why so many ammonite specimens from the upper Cretaceous are damaged in a particular part of their shell; he suggested that this was evidence of predation, where the shell was pierced by predatory cephalopods to extract the body parts from within.