SABRINA TIMES September 2017

OPEN UNIVERSITY GEOLOGICAL SOCIETY SEVERNSIDE BRANCH

Branch Organiser’s Report Hello everyone, I hope you have all been enjoying the summer season and taking the opportunity to indulge in some outdoor geology, perhaps while on holiday in the UK or overseas. Since the last newsletter we’ve had a very successful trip, in perfect weather, to Chedworth in the Cotswolds with Dr Paul Olver and you will find a report inside this newsletter. This perfectly organised trip included the opportunity to enjoy a delicious bacon butty and cup of coffee in the warm sunshine at Chedworth Farm Shop’s café before we set off on our geological excursion ! OUGS Symposium Over 180 delegates attended the annual OUGS Symposium in August, which was held at Queen Margaret University in Edinburgh. The very successful weekend programme of ten lectures demonstrated the great diversity of Scotland’s geology and landscapes, and covered topics that ranged from Scottish dinosaurs to lava fields and post-glacial shaping of the Scottish mountains. A particularly topical lecture described the engineering geology associated with construction of the new road bridge over the Firth of Forth, formally known as the Queensferry Crossing, which opened to traffic on August 30th, just over a week after our Symposium weekend. There were also many field trips to choose from on the Saturday afternoon and Monday, including visits to famous sites such as Siccar Point, Dob’s Linn and Arthur’s Seat. One of the speakers at the Symposium was Professor John Underhill, Chief Scientist at Heriot-Watt University. John hit the headlines in many newspapers a few days before the Symposium when he entered the fracking debate by suggesting that fracking in the UK may produce less fuel than currently forecast. This is because the UK’s shale- bearing rocks have been uplifted, tilted and deformed by geological changes over the last 55 million years, unlike the relatively stable and undeformed shale basins in the US. Towards the end of his excellent symposium lecture on the evolution of the Midland Valley, John mentioned the controversial topic of oil and gas extraction from shale, which not surprisingly led to much discussion afterwards! John’s essay on fracking is available via this link: https:// theconversation.com/there-may-be-a-huge-flaw-in-uk-fracking-hopes-the-geology-80591

Day of Lectures and Branch AGM Our branch Day of Lectures will take place on Saturday 25th November at the National Museum of Wales in Cardiff. Jan has excelled herself this year by arranging four eminent speakers, three of whom are professors! The Museum is also the venue for our branch AGM on Saturday 20th January 2018, and our thanks go to the Museum’s authorities for kindly waiving room hire charges for both events. Forthcoming Field Trips We have two more field trips planned for this year. The first one will take place on 24th September at Blaen Onneu limestone quarry in the Black Mountains, led by Prof Paul Wright. This will be a joint trip with the Mid Wales Geology Club. Earlier this year Paul led us on an excellent trip to Three Cliffs Bay in the Gower to examine a carbonate ramp, and this trip to Blaen Onneu should be equally good. Our last trip of the year on 15th October will be led by Dilys Harlow to Gilwern Hill and Clydach Gorge, a few miles west of Abergavenny, and promises to be full of geological interest. I hope you’ll be able to attend our forthcoming events, and look forward to seeing you there!

Best wishes, Norman Nimmo-Smith Inside this issue: Chedworth 2 Siccar Point 6 Events 8 Contacts and Editorial 13

D34 Chedworth 2nd July 2017

Leader: Dr Paul Olver, assisted by Sue Olver.

Introduction The village of Chedworth is situated in the Cotswolds, about 7 miles north of Cirencester. During the day we visited two sections of the abandoned Cheltenham to Cirencester railway line near Chedworth, as indicated on the map in Fig. 1, and examined carbonates of the Middle Jurassic period. A stratigraphic column of the Jurassic carbonates in the Chedworth area is shown in Fig. 2.

Fig. 2 Stratigraphic column showing relationships of Mid Fig. 3 The limestone exposure at Stony Fig. 1 The two locations visited in the Jurassic carbonates seen at Furlong Quarry. The dotted line shows Chedworth area Chedworth sites the position of a disconformity

Stony Furlong Quarry Seventeen OUGS members assembled at Denfurlong Farm Shop Cafe, Chedworth, GL54 4NQ (Grid Ref. SP068105). From there we walked across the farm campsite, located on an infilled quarry, over the embankments and sidings of the old railway line bed to reach the abandoned Stony Furlong Quarry. The railway was opened in 1891 as part of a link between the Midlands and Southampton, and continued in operation until 1961. The quarries either side of the line at this location supplied stone for railway ballast and construction of the WWII RAF Chedworth airfield. This left Stony Furlong Quarry with a c.10 metre high exposure (Fig. 3) through the 165 Ma Great Oolite White Limestone Formation. The limestone was laid down in warm marine conditions in an offshoot of the Tethys Ocean that covered Southern Europe when England was at c. 35 - 40°N. The quarry wall’s upper, very pale, harder, horizontal and well bedded Ardley Member is separated by a disconformity, representing a change in deposition environment, from the lower, browner, more iron-stained Shipton Member. Both are oolites, indicating warm, shallow sea water deposition, but the sparite-cemented shell debris of brachiopods, tiny fragments of vertebrae and spines of burrowing echinoids in samples of the Ardley Member collected from the base of the face, and seen in situ in a large fallen cliff block (Figs 4, 5 and 6), indicated deposition in an open marine environment. In comparison, the browner Shipton Member beneath was more weathered with peloidal grains in a marly matrix enclosing only brachiopod fragments and black specks and threads of dendritic manganese. This suggested lower biodiversity and a more saline, restricted, environment for the Shipton, before a marine incursion and the Fig. 4 Malcolm attacking a block of Ardley oolite that had deposition of the overlying Ardley oolite. fallen from the upper part of the quarry face

2 Chedworth 2nd July 2017 (contd,)

Fig. 5 Ardley oolite with shell and Fig. 6 Ardley oolite with large shell black vertebrae fragments fragments

Fig. 7 Sketch map of Chedworth railway track bed route with locations of geological interest A to I.

Railway Cutting Having spent time collecting, comparing and discussing the significance of samples, we drove to the National Trust Chedworth Roman Villa near Yanworth for lunch at the visitor centre and the possibility of a visit to the Villa site. The geological features of interest were located along a section of the same railway line seen in the morning, and accessed from a footpath leading westward from the visitor centre – see sketch map, Fig. 7. The rock exposures represented the Inferior Oolite succession immediately below the Great Oolite seen earlier at Stony Furlong Quarry. It was rather overgrown and shaded by trees on some stretches, because it was midsummer, so some diligent searching was required. Considerable aid by Sue Olver in finding suitable places to search was helpful – she had obviously been there before ! Our route lay on the track bed within the Chedworth Wood Nature Reserve, and we walked to location A at the south end first. The tunnel entrance there is walled up for safety and to provide protection for the bats that inhabit it (Fig. 8). The upper surface vegetation and soil of a muddy calcitic iron-rich layer marked a disconformity below the eroded-away Fullers Earth. Below was a coarse oolitic limestone with colour and texture variations suggesting changing current speeds. A trace of a burrowing organism and a few shell Fig 8: Location A on the railway cutting, at fragments of a burrowing echinoid (Clypeus sp.) were found. This was the the walled-up tunnel entrance, with Paul Clypeus Grit of the Salperton Formation, at the top of the Inferior Oolite Olver telling us where to find the best succession. Its composition and fossils indicated a deposition environment fossils of deep, offshore, current-affected water.

3 Chedworth 2nd July 2017 (contd,)

Further on along the track, at location B, calcite deposits encrusting the mosses and liverworts in a mound around a small flowing spring demonstrated how calcitic tufa develops today – a rock much used by Victorian landscape gardeners to create rock garden grottoes (Fig. 9). At location C we found an oolitic Fig. 9 Tufa Waterfall with mosses and bed containing a pyramidal bivalve, liverworts (courtesy of Linda Fowler) Trigonia costata. This oolitic bed, the Upper Trigonia Grit, lay parallel with the overlying Clypeus Grit and above an underlying unconformity with pale grey Notgrove Freestone (Fig. 10). The eroded upper surface of the Notgrove Freestone was marked by round pin-head size tunnel openings that had been created by the action of juvenile silica-shelled Pholas sp. or piddocks. These bivalves had toothed margins Fig. 10 Janet helpfully pointing out that enabled them to bore into the oolitic Notgrove surface as they rotated. the unconformity between the Upper The rock gave them protection as they filter fed and excreted via siphons Trigonia Grit (upper unit) and Notgrove projecting from their tunnels (Fig. 11). Freestone (lower unit)

Fig. 11 Small holes in Notgrove Freestone produced by the Fig. 12 Field sketch of the normal fault on the “boring fossil” Pholas western bank of the cutting at location G

Further south along the track bed at location G, the Clypeus Grit is normally faulted and down-thrown against older beds, as shown in Fig. 12. This resulted in Gryphite Grit and orangey-brown peloidal Lower Trigonia Grit on the other side of the fault, and we found fragments and prints of specimens of the bivalve Gryphaea embedded in the Gryphite Grit (see Fig. 13). Further south on the track, at H, an exposure in a deep cutting gave a continuous stratigraphic section including the oldest rocks seen during the day. At the base of the c.10 m face was pale grey, fine-grained, micritic Scotsquar limestone with Harford sandy clay overlying it, both belonging to the Birdlip Limestone formation.

Fig 13: Evidence of Gryphaea in the aptly named Gryphite Grit (courtesy of Linda Fowler) 4 Chedworth 2nd July 2017 (contd,)

The limit to our investigations along the railway cutting was at location I, and the route took us along a spectacularly elevated embankment which crossed a small, deep valley. Here the Clypeus Grit was marly and less well cemented than seen previously at location A, suggesting deeper water deposition. We found clearly recognisable parts of sea urchin shells and their imprints preserved in this less current-dominated environment, as well as a good example of the elongate bivalve Gervillellla (Fig. 14)

Fig. 14 The elongate bivalve Gervillella

This walk along the railway cutting allowed us all to see evidence of changing environmental conditions for the biota and sediment production that indicated the tectonic and sea-level changes in the Jurassic from 165 -175 Ma at the time of the Alpine orogeny. In very hot July weather the location provided an interesting field day that would be worth investigating further in the months when the vegetation is sparser. After returning to the Roman Villa visitor centre for tea and cakes, we thanked Paul for leading us on a very interesting and enjoyable trip in the Cotswolds.

Report by Janet Hellen

5 Hutton’s Unconformity at Siccar Point

21 August 2017 One of the field trips arranged on the Monday after the Edinburgh Symposium was to Siccar Point, which is situated on the Scottish coast about 30 miles south-east of Edinburgh. This is the famous spot where, in 1788, James Hutton found the clear evidence he needed to demonstrate his understanding of the processes and cycles that shaped the Earth. Along with two companions, John Playfair and Sir James Hall, Hutton had sailed along the coast looking for the join between the folded rocks of the Berwickshire coast and the flatter lying sedimentary strata that formed the East Lothian coastal plain, and found this at Siccar Point (Fig 1). Not surprisingly this trip to the “geologists’ Mecca” proved to be a popular pilgrimage for those attending the Symposium. Two separate groups were necessary and my group visited Barns Ness in the morning before heading off to Fig 1: Hutton’s famous unconformity at Siccar Point, with the near Siccar Point after lunch, whilst the other group vertical Silurian greywacke lying below the younger near horizontal spent the morning at Siccar Point. We were very Devonian sandstone (pen for scale) fortunate to have Professor Stuart Monro as our leader – Stuart is a prominent Scottish geologist and was a part-time OU tutor for many years. The classic view of Hutton’s unconformity lies close to sea level at Siccar Point and can only be approached by descending a steep slope (Fig 2).This didn’t deter most of the party who bravely descended with the aid of a fixed rope (of unknown pedigree) and a wobbly fence as handholds. Happily there were no mishaps. At the bottom Stuart paid his respects to the hallowed and much photographed unconformity between vertical Silurian greywacke and near horizontal Devonian sandstone (Fig 3), which represented a gap in deposition of over 50 million years.

Fig 2: Climbing down the steep slope at Siccar Point to reach Hutton’s unconformity at sea level

Fig 3: Prof Stuart Monro paying his respects at the site of Hutton’s Unconformity at Siccar Point

6 Hutton’s Unconformity at Siccar Point (contd,)

Stuart then asked us to sit down around the unconformity while he read aloud John Playfair’s account of the visit to Siccar Point in 1788. Here Hutton revealed to Hall and Playfair the true significance of what they were seeing. He recognized that the vertical rocks would have been initially laid down horizontally then subsequently squeezed into a vertical position forming large-scale folds and building mountains. Before the second gently dipping rocks were laid down there would need to be a long period of erosion, removing the mountain. Finally the second set of rocks would be laid down. The unconformity between the two sets represents, therefore, a period of time when mountains were raised and then eroded away. Stuart reminded us that these observations should be seen in the context of the established wisdom of the time, that of Archbishop Ussher of Armagh who pronounced that the world was formed on the evening prior to the 23rd of October 4004BC. Hutton demonstrated to his friends at Siccar Point that the Earth had to be very much older. We now know that the greywacke sandstone formed on the floor of the Iapetus Ocean around 430 million years ago, and was later compressed and upended during the closure of the ocean basin at the time of the creation of the great Caledonian mountain chain. The red sandstone came much later, around 380 million years ago, when the Caledonian mountains were eroding and large river systems brought sediment south into the broad, subsiding Midland Valley. The resultant unconformity between greywacke and sandstone could be seen in various places around Siccar Point (Fig 4).

Fig 4: A view of the unconformity between red sandstone and greywacke in the cliff at Siccar Point

The return journey up the steep slope to the cliff-top was hard work, but happily uneventful, and we were able to enjoy the fine views along the coast when we reached the top (Fig 5). Before heading back to Edinburgh we thanked Stuart for making this a most memorable day.

Fig 5: Enjoying the views from the cliff-top at Siccar Point

Report by Norman Nimmo-Smith

7 Severnside Branch Events

2017 EVENT LEADER DETAILS To study the Carbonate sequence September 24th Blaen Onnu quarry Paul Wright

Gilwern Hill and Clydach Gorge October 15th Abergavenny Dilys Howell

Oriel Suite, National Museum of Wales, Cardiff Prof. Paul Wright, from Natural Sciences, National Museum of Wales, and PW Carbonate Geoscience: "Four kilometres below the Atlantic sea floor: Brazil’s bizarre Pre-Salt oil fields"

Prof. Maurice Tucker, from Bristol University: "The Trouble with Dolomite - where are we?" November 25th Day of Lectures Prof. Sue Marriott, Visiting Professor at Bristol University: "Microbes in the Silurian and their influence on sediment deposition and sedimentary structures in the Old Red Sandstone"

Dr. Chris Berry from Cardiff University: "In search of the lost Devonian forests of Svalbard” Explore and examine the geology of this volcanic island December 9th-16th Fuerteventura Linda Fowler Waiting llst only Contact Jan Ashton-Jones if you wish to add your name 2018 Oriel Suite, National Museum of Wales, Cardiff January 20th Severnside AGM

Event Notes

EVENT DETAILS CAN CHANGE Any last-minute changes of times or arrangements are on the OUGS website.... www.ougs.org Or...... Contact Norman Nimmo-Smith - 01684 891859 [email protected] If you are not receiving email reminders from Norman regarding forthcoming events or if you get a new email address please let him

Transport If you are able to offer a lift to any event or if you have local knowledge regarding bus or train services etc. that might help those without their own transport to attend an event please let Janet know. Updates Why not try the following link to a service for keeping an eye on changes in the events list. http://www.changedetection.com

THERE IS A NOMINAL FEE OF £3 ON DAY TRIPS (UNLESS OTHERWISE STATED) TO COVER LEADERS EXPENSES. ALWAYS WEAR APPROPRIATE GEAR...WARM CLOTHING AND HIKING BOOTS. BEAR IN MIND THAT MANY SITES, ESPECIALLY QUARRIES, REQUIRE THE WEARING OF HARD HATS. ACTIVE QUARRIES REQUIRE HARD HATS AND YELLOW JACKETS. IT IS RECOMMENDED THAT PARTICIPANTS BRING HARD HATS TO ALL FIELD TRIPS - JUST IN CASE !

IMPORTANT Each person attending a field meeting does so on the understanding that he/she attends at his/her own risk. The OUGS has Public Liability Insurance cover for field and indoor meetings but Personal Accident and Personal Liability cover remain the responsibility and personal choice of the participant. There may be an element of appropriate cover included in house or travel insurance. Although OUGS activities are not particularly dangerous members are advised to check whether exclusions apply to activities in which they propose to participate in case they wish to arrange further cover. An annual travel insurance may be the best solution for any member who regularly attends field events. This is again a matter of personal choice. All members participating in overseas events will be required to have travel insurance for the duration of the event. Participants should be covered for Medical, Repatriation and Personal Liability expenses. The Personal Accident element remains the personal choice of the member. Disclaimer None of the information in any of the advertisements for field trips or other events in this newsletter constitutes a brochure under the Package and Travel Regulations (1992)

8 Geologists Association Conference 2017

9 Hydrock William Smith Lecturev2017

10 Mendip Rocks !

11 Branch Library - an update

The Nature of Diamonds George E. Harlow 1997 288 pages The paragon of physical perfection and a sparkling example of Earth's forces at work, the diamond has fascinated all realms of society, from Russian tsars and Hollywood stars to scientists and brides-to-be. The Nature of Diamonds is an authoritative and richly illustrated look at nature's most coveted gem. Leading geologists, gemologists, physicists, and cultural observers cover every facet of the stone, from its formation in the depths of the Earth and its explosive ascent to the surface, to its economic, regal, social, and technological roles. The book takes the reader to cutting-edge research on the frontiers of diamond exploration and exploitation, from Arctic wastes to laboratories that create industrial diamonds for cutting tools that slice through rock. Charting the history of mining from its origins in India and Brazil, the book follows the diamond rush in South Africa to today's high-tech enterprises. It provides a glimpse into the economics of the diamond trade, and an overview of diamond cutting, from the rough uncut stones in early Indian and Roman jewelry to the multifaceted stones we see today. The cultural history of the diamond as both a revered and a social symbol is explored, from its early history as the exclusive property of royalty to today's brilliant-laden jewelry as an emblem of wealth and status. The engaging text is complemented by more than 200 lavish illustrations which span fine art, earth science, and cultural studies and capture the brilliance and beauty of this extraordinary gem.

Roadside Geology of Oregon 2nd Edition Marli B.Miller 2014 386 pages This second edition is based on the most up to date understanding of Oregon’s geology. Spectacular photographs showcase the state’s splendour while also help the reader to understand geologic processes at work. Active volcanoes, ghost forests, landslides and towns heated by geothermal energy attest to Oregon’s prominent position at the edge of an active tectonic plate.

London - Illustrated Geological Walks - Book 2 Eric Robinson 1985 142 pages Following the pattern of Book 1, dealing with the city, Book 2 moves into the lesser known streets of the West End, Here we find a wide range of exotic rock types as we examine the modernised shop fronts of Piccadilly and Tottenham Court Road and the newer office blocks of Central London.

12 Severnside’s OUGS Neighbours and other Organisations

It’s worthwhile taking a look at what other branches are doing. Many of their events could be convenient to attend. OUGS Oxford Branch Organiser: [email protected] OUGS Southwest Branch Organiser: [email protected] OUGS Wessex Branch Organiser: [email protected] OUGS West Midlands Branch Organiser: [email protected]

Many of our members belong to other Earth Science related organisations which also do interesting events; Welsh Stone Forum http://www.museumwales.ac.uk/en/364/. Geologists Association [email protected] Affiliated Regions: South Wales www.swga.org.uk West of England www.wega.org.uk Bath Geology Society www.bathgeolsoc.org.uk Avon RIGS Group The Avon RIGS Group are re-launching their newsletter, Outcrop, as an on-line blog. The relevant websites are: www.avonrigs.org.uk http://avonrigsoutcrop.blogspot.com

South East Wales RIGS Group Contact Nigel McGaw 01656 654439 [email protected]

The Russell Society www.russellsoc.org.uk

Teme Valley Geological Society Based in Martley, Worcestershire http://www.geo-village.eu

OUGS Severnside Branch Committee

Norman Nimmo-Smith - Branch Organiser 01684 891859 [email protected] Averil Leaver - Treasurer 01446 418592 [email protected] Jan Ashton-Jones - Events co-ordinator 01432 860736 [email protected] Janet Hiscott - Librarian 01633 960845 [email protected] Jan Boddy 01793 762575 [email protected] Kath Addison-Scott 01179 538085 [email protected] Anthony Bukowski 02920 300080 [email protected] Linda Fowler 01432 860465 [email protected] Teresa Jenkins 07542 895244 [email protected] John de Caux - Newsletter Editor 01633 875955 [email protected]

Editorial

If you are one of the remaining members still receiving Sabrina Times by post why not get the much better colour version of this and future issues of the newsletter by email (in .pdf format). Just send a request to your editor at: [email protected] Contributions for the newsletter will be very welcome from members, as will any comments or suggestions for improvement. We are able to read or scan most data formats or documents. For photos please send the images as separate files, preferably in jpeg (.jpg) or bitmap (.bmp) format with notations in the text. For large files OneDrive or Dropbox may be used…...just email the editor a link.

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