E 17 July 2007 Severnside Branch SSaabbrriinnaa TTiimmeess Branch Organiser's Bit I have just reviewed my last piece for the newsletter and find I made a comment about how the weather would surely be better for our May fieldtrip. How wrong I was! Although the day before had been lovely, Sunday 13th May was very overcast and wet. The Cat's Back was not visible through the cloud but I was impressed by the number of members who turned out in such weather. It was great to see you all. Also, well done and thank you to Duncan who was able to offer us an alternative, lower route, avoiding the cloud if not the rain, and still filled the day with interesting Ever wonder where the exposures. “Sabrina” name comes Our trip to in June was fully booked; from? Here's your answer. as is the week’s trip to Kindrogan in July. Unlike One of a series of carved the Cat's Back trip, the weather for Flat Holm oak statues near the Old was good. It was an excellent day out, and I'd Railway Station, Tintern, like to thank Chris Lee for guiding us. it is dedicated to the Jan and Linda are running a shoestring trip to legend of the Celtic the Sierras in Central Spain in September. goddess, whose latinised There are still spaces on this. In addition to the name is Sabrina. The geology there are many medieval towns in the inset is of the signboard area to explore; not to mention Madrid. near the statue. I hope you enjoy the summer (when it arrives) and get out there to see lots of rocks. For Photos: Jan Ashton-Jones those of you who are studying, good luck with those TMAs, and remember that a day out in Commiittee Contacts the field really does support your studies and Branch Organiser: Janet Hiscott – 01633 781557 (eve) [email protected] increases your understanding of the subject. So Treasurer: Elizabeth Freemantle – 02920 709905 [email protected] don’t feel too guilty about taking a day off and Ordinary members: joining OUGS on one of our fieldtrips. After all, it Jan Ashton-Jones (Events) – 01432 870827 [email protected] is the main purpose of the Society to provide Jan Boddy – 01793 762575 [email protected] field experience for OU students which the Anthony Bukowski – 02920 300080 [email protected] university itself is not in a position to organise. Philip Clark (Library) – 01982 560735 [email protected] The next National event is the Symposium which Elizabeth Edmundson (Newsletter) – 01792 863119 Sa brinaTimes@aol. com is being held in Lancaster this year. In a Scott Jones – 01495 755004 [email protected] change from the traditional dates, this year it is Helen Williams – 01495 774520 [email protected] taking place in August. Perhaps I will see some of you there? Committee member Jan Boddy, working Janet Hiscott hard on all our Remember, I can be contacted via e-mail on behalves. [email protected]. Photo: E. Edmundson

Pg 1 On all emails, please put “OUGS Ssi” in the subject or title space, to avoid getting deleted as spam! Sabrina Times July 2007 Editorial Library This issue is a short one and it's late... my excuse As promised, here is the next part of our list of library books: this time is a hard drive failure. You know how it is – Librarian: Philip Clark 01982 560735 [email protected] install a new one, and the d****d thing “updates” ➢ ENVIRONMENTAL GEOLOGY everything, loses stuff and generally creates Coasts Hansom, J.D. electronic mayhem. Of course, it's not always the Cretaceous World, The; Skelton, P. machine's fault. What's obvious to the completely Great Ice Age. The; Wilson, R. et al. computer-savvy amongst you isn't always apparent to Holocene, - An Environmental History. The; Roberts, Neil the merely computer-literate – like me. So I'm Human Impact on the Natural Environment. The; Goudie, A. experimenting with a new look ST in the hopes of Pleistocene Environments in the British Isles; Jones, R.L. & Keen, D.H. streamlining the editing job and reducing the package Urban geology and Earth heritage conservation – Geology on your doorstep; size for electronic mailing (I have been laying out the Bennett, M.R. & Doyle, P. newsletter for printing only, so how many megabytes Urban Geology in ; National Museum of Wales it is has not been quite so important).

The most important change is in the publicity for our ➢ SEDIMENTLOGY events. The Events Diary remains, but the adverts Applied Sedimentology; Selley, Richard C. page is changed to a Details page. This is easier to Desert Aeolian Processes; Tchakerian, V.P. produce; and to revise, if needed. Both of these Petroleum Geology of the North Sea; Glennie, K.W. pages will advertise Branch events only - this Petroleum Geology; North, F.K. includes Shoestring trips and joint trips with other Principles of Sedimentology and Stratigraphy; Boggs, Sam Jr. Branches. The Diary will, however, list the dates of major national OUGS events as well. ➢ TECTONICS Events organised by other Branches and by non- Geological Evolution of Ocean Basins; Cramp, A., MacLeod, C.J., et al. OUGS societies will no longer have their events lists Geological Structures and Moving Plates; Park, R.G. provided in the ST. There are two good reasons for this: 1, this is only a branch newsletter, produced by volunteer efforts, and we cannot be expected to give OUGS Neighbours everybody publicity; and 2, gathering relevant details Those of you living near any of these regions ought to keep in touch with what they're is very time-consuming. Lists of nearby OUGS doing. Many of their field trips will be conveneintly nearby and it's always good to get branches and non-OUGS organisations, with field experience. Of course, a full list of all Branches appears regularly on page two of the website/contact details will appear in future STs. Any National Newsletter. Ssi member who is involved in an Earth Science society, who would like it to be included may send me OUGS Gogledd Cymru their info, and a short sentence about that group. B.O. Rachel Atherton 01942 270152 [email protected] Write-ups will also be shorter. Most write-up OUGS oxford volunteers are doing OU courses; it's unfair to ask B.O. Sally Munnings 01635 821290 [email protected] them to pen the equivalent of a TMA answer! I'd like to increase the number of photos. If you have a good OUGS Southwest shot of a geological feature from one of our field B.O. Gordon Neighbour 07930 849622 [email protected] trips, send it in, along with a few sentences about it, OUGS Wessex and your first and last name (photo credit). B.O. Sheila Alderman 01935 825379 (eve) [email protected] Lastly, some very bad news indeed... there's no OUGS West Midlands Trilobite Hash cartoon gracing the last page. B.O. Linda Tonkin 01902 746074 [email protected] WHAT? What about Non-OUGS Organisations my freedom ➢ Welsh Stone Forum – Our Librarian, Philip Clark, is an active member of the WSF. To find out more, get in touch with him at 01982 560735 or [email protected] of speech? ➢ South Wales Geological Association – website www.swga.org.uk ➢ West of Geological Association – website www.wega.org.uk ➢ Central Wales RIGS – website www.geologywales.co.uk/central-wales-rigs ➢ Geological Association – Secretary Sarah Stafford 020 7287 0280 [email protected] ➢ The Russell Society – The RS is a mineralogical interest society; I believe it is based Sorry 'bout that... in South Wales. The only contact number I have is: E. Edmundson (Editor) Lynda Garfield [email protected] Pg. 2 If any of you are members, and have more complete contact details, please get in touch. Sabrina Times July 2007 Events Diary Please note: There is a nominal fee of £2 on day trips (except when otherwise stated) to cover leader's expenses. Events are organised by Jan Ashton-Jones, unless there is a different contact name given. You can ask her for details at: 01432 870827 or [email protected] 2007 ➢ July 23 – 31 Two-day Oceanography Experience trips – OUGS – Three two-day sessions available (Southhampton). Contact: Sheila Alderman at 01935 825379 Email: [email protected] ➢ August 17 – 19 OUGS Symposium (Lancaster ) - Contact: Chris Arkwright 01772 335316 Email: [email protected] ➢ September 4 – 11 Sierras on a Shoestring (Leader: Mark Anderson) – Joint trip with Southwest Branch - Contact: Jan AJ ➢ September 23 Building Stones of Newport (Leader: Stephen Howe) – Contact: Jan AJ ➢ October 21 Tintern Quarry, Forest of Dean (Leader: David Owen) – Contact: Jan AJ ➢ November 17 OUGS AGM (Northampton) – Contact: Polly Rhodes 01420 475548 Email: [email protected] 2008 ➢ January/February Day of Lectures (National Museum of Wales, ) - Contact: Jan AJ ➢ March (?) Introductory Day (Leader: Dave Green) ➢ March/April (?) Volcanoes on a Shoestring – Tenerife (??????) - Contact: Jan AJ For all field trips Always wear appropriate gear... warm clothing and hiking boots. British weather being what it is, be prepared for that, too.

Important Notice "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 Cover and Personal Liability Cover remain the responsibility and personal choice of the participant. There may be an element of appropriate cover included in house insurance or in travel insurance: although OUGS activities are not particularly dangerous members are advised to check whether exclusions apply to activities in which they plan 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 again is a matter of personal choice. Please note however that all members participating in overseas events will be required to have travel insurance for the duration of the event: this is so that participants are covered for Medical, Repatriation and Personal Liability expenses. The Personal Accident element remains the personal choice of the member and again members are advised to check exclusions so that they can make an informed decision about the cover they want.”

We wish... Island Future week-long residential trips to Lundy will be organised independently of Severnside Branch. We will keep you informed.

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Not the Cat’s Back – Sunday, 13 May Branch trip to Flat Holm. Courtesy of the Flat Holm project. The Black Hill car park is not the easiest to find, but a dozen members Leader: Chris Lee, University of .

arrived there on a wet and windy Sunday morning to meet Duncan Hawley th for another venture into the Old Red. This is higher up the succession 29 members, friends and family met in Cardiff Bay on 10 June. The trip than our last excursions with him based on Talgarth and Erwood. But it out to the island on MV Lewis Alexander took us across the Bay and was not difficult to agree that the weather prospects meant that the climb through one of the three small-vessel locks that operate every 20 - of an arête onto the Senni Formation, which forms the heights of Hay minutes. A diversion along the coast to allowed us a seaward Bluff - would not be prudent. So we went on to Hay-on-Wye and, after view the unconformity there. En route there were fine views of the gently consolidating into as few vehicles as possible, Cusop Dingle (on the folded strata more usually seen from the foreshore at and Barry. boundary between England and Wales). We were thus back in the Raglan Flat Holm sits in the middle of the Channel and is composed of Mudstones ( the old Downtonian) which we had seen with Duncan on the limestone laid down during the Visean stage of the Carboniferous. The two previous trips. As Duncan has done pioneer fieldwork in Cusop Dingle stratigraphy (see below) shows how it relates to familiar exposures found and the other areas, this was highly satisfactory – it’s always so elsewhere in South Wales and on the other side of the channel in the West instructive to be with someone who has actually contributed personally to Country. It is a gentle antiform and is presumed to be a continuation of our understanding of a location. the -Portishead anticline. The geological map shows several There were of course problems with this locality just at the time: the small faults with a thrust to the south of island where some small folds vegetation, the height of the water in the stream, and not least the were visible during our later circumnavigation. irruption of the wretched natural gas pipeline which is scarring South Regional Stages (Weston-super-mare) Wales. Even this last, however, has its compensations. Duncan had helped ensure that where it crosses the important site (a future SSSI for Holkerian Clifton Down Limestone geological reasons) the pipeline tunnels under the stream, and so we Goblin Combe Oolite were able to look into a great pit and see some of the features in clean, totally unweathered, exposures. Along the Dulas Brook and its tributaries Birnbeck Limestone

there are over 200 m exposed of the Lower Old Red – with the Sawdde N Arundian

A

Gorge at the other end of the Brecon Beacons National Park, the most E

S Flatholm Limestone

I

continuously exposed inland section of this interval in the area. V Duncan explained how it was that these lowest units of the ORS are now Caswell Bay Mudstone classed as Silurian, not Devonian. The fossil evidence for the division into Gully Oolite biostratigraphic units which are sufficiently important to mark system Chadian changes is lacking in our largely non-marine facies, but appear in the Black Rock Dolomite Czech type localities which have “Prídolí” as the universal series name. Flat Holm's stratigraphy (from notes supplied by Chris Lee) There are successions of sandstones and siltstones, some of the former The island is an SSSi and a nature reserve with over 4000 seabirds (hard with desiccation cracks. Duncan and Geraint Owen have interpreted these hats are advised to protect against gull attack). For a short visit there is as “broad bar forms and low relief dunes in a high-sinuosity, laterally much to see: Napoleonic guns through to World War II fortifications; a migrating river channel subject to variable discharge, which occasionally Victorian water collection and storage system; lighthouse and (now dried out completely.” defunct) buildings; There is a small museum displaying the plans Some way up the dingle, a pale rock– the Townsend Tuff - appears in the of a sanatorium and the evidence of many centuries of habitation . streambed. Duncan made us work out why a series of three volcanic ash Marconi made his first wireless transmission from here to . falls was particularly significant – a marker bed, chronostratigraphic horizon, chronohorizon – whatever you call it, and it’s also known as key bed and datum, a bed which appears over a wide area of South Wales and into England and proves the deposits to be contemporary. If you look on the new sheets 197 and 214 of the BGS 1:50 000 maps you will see “local details supplied by D Hawley, University of Wales, Swansea” – that’s fame. He told us how he had worked out from dip and altitude where the strike should be exposed in other streams – and proved it to be so. The source of the ash may well have been a volcano to the west, in what are now the Alleghenies. Nearly at the top of our wet walk appeared a 4 m thick bed overhanging a waterfall – the Bishop’s Frome Limestone, formerly known as the Psammosteus Limestone. This massive calcrete palaeosol (not The geological high point of the day... World-class mega ripples! everywhere so thick) marks the point where the Raglan Mudstones pass Photo: Janet Hiscott into the St. Maughan’s Formation (the old Downtonian into the Dittonian) If you have an interest in oceanography, you would have enjoyed the and again is a regional marker bed. It represents a very long hiatus in discussions arising from observations of the impact of the barrage across deposition, perhaps as much as 100,000 years. We had already seen old Cardiff Bay. With a range of bird life visible, the waters are clearly limestone kilns, as helpful a guide to the geological enquirer as limestone productive, despite the restrictions on inflowing seawater. We landed on loving plants like the early purple orchids beside the track. the Island on a rising and were able to look down and see mixing and Philip Clark eddies as brown muddy waters met cleaner water coming downstream. Pg. 4 Janet Hiscott Sabrina Times July 2007

Lundy Island – 19 – 26 May On the trip this year, maps for annotation of the area north of the Three Lundy Island, in the , is a coarse-grained white-and-biotite Quarter Wall were made available to anyone wishing to take part in the granite laccolith, with a bit of Ordovician slate (country rock) on its search for more of the pink granite. One party found some stone used in southeastern tip. The granite is criss-crossed by dykes and veins; aplite, the Three Quarter Wall had bright pink areas; another party re-examined basalt, etc.; and of course, lundyite. the Frenchman’s Landing site and decided that it was a chemical weathering effect and several parties looking for pink, noticed weathering ranging from coral to maroon in colour in granites exposed in various The Lundyite Dyke on different areas of the Island. the southeast of the On this trip, the new Warden enforced the present restrictions on a island (a) props up collection of fresh samples from the east coast due to the “No Take Zone” b the mainly granite- imposed by English Nature however, this is defined as “No fishing or and-slate promontory th collection of sea life of any kind”. I shall write to English Nature before the (b) for the 12 C next trip to have this clarified and to request permission for a small castle on top. c sample for further analysis. The Ordovician slate Sara Whitley-Kinzett MSc Mst (c) is less weather- resistant. Photo: E. Edmundson

Lundy's granite contains an array of interesting minerals, and is a real must-see for granite fans. It varies in grain-size and composition. In recent years, we've been following up the occurrence of a rose-pink granite. Guest writer Sara Kinzett (Northeast Branch) gives a resumé: Pink Granite Search – Lundy 2007 According to the Good Britain Guide, the journey to Lundy was voted “Boat Trip of the Year” – but just not this year according to the fourteen OUGS members that made the trip. Granite, granite everywhere... most of Lundy's buildings are built of - On the trip six years ago, Liz Edmundson had noticed a large boulder of you guessed it – granite! There are several disused quarries, like pink granite embedded in the road on the way to the North Light. I was this one. Photo: E. Edmundson asked to confirm her find and enter into a discussion about its origin. I Future Trips? photographed it and decided that it was not Norwegian ballast but was Our week in Lundy was a pleasant, leisurely one, but – apart from our puzzled that the cooling of this block had produced a granite similar in pink granite project - unstructured as far as geological fieldwork or construction to the rest of the area. observation was concerned. We all pursued other interests as well – bird- On the trip four years ago, I was photographing the coastline for the watching, wildflowers, insects, sealife - and many of us felt that we were Lundy CD and came across some small weathered pink outcrops on the taking undue advantage of the Branch's (and National's) facilities. There east coast north of The Mousehole at Gannet’s Bay. was some discussion as to forming a special interest group, and going next time as an independent party. Lundy is a great place, full of On the trip two years ago, we had the pleasure of Clive Roberts’s geological interest (see page 6 for two features), so we will be going company and he agreed to search for the pink granite at Frenchman’s again. We'll keep you informed. Landing. The party found some outcrops of granite and samples were E. Edmundson sent to the OU laboratories for testing. The results are not yet available.

Frenchman's Landing Photo: Mark Reed Pg. 5 Sabrina Times July 2007 Details of Field Trips and Events

✔ September 4 – 11 - Sierras on a Shoestring - Leader: Mark Anderson Joint trip with Southwest Branch. The Central Spanish Sierras Metamorphism of granites & sediments; later granites # Permian collision: younger sediments & ongoing erosion # Quaternary glaciation Based at the Hotel La Barranca, Navacerrada, 30 minutes NW of Madrid. Contact: Jan Ashton-Jones 01432 870827 [email protected]

✔ September 23 – Building Stones of Newport – Leader: Stephen Howe Details of this trip will be in the next Sabrina Times (late August/ early September). Contact: Jan Ashton-Jones 01432 870827 [email protected]

✔ October 21 – Tintern Quarry, Forest of Dean – (Leader: David Owen) A huge disused quarry exposing . More details later. Contact: Jan Ashton-Jones 01432 870827 [email protected] Jan AJ is busy working out details of a whole list of events. The next issue of the Sabrina Times will have a much fuller list. Sadly, the planned trip to Korea has been cancelled. The trip leader, Bill Fitches, is unable to make it. However, another very promising overseas trip is on the horizon - WATCH THIS SPACE! The new National OUGS website launches in August, with the August edition of the National newsletter. It will contain a complete events list, and links to Branch websites. Severnside Branch needs a WEBMASTER to manage the Branch website. It's not rocket science; all you need is Internet access and ability to use Word. CAN YOU DO IT? Get in touch with Janet Hiscott at [email protected]

The newsletter is now available as a PDF file for distribution by e-mail. There are many advantages to this: you could receive it up to a week earlier than the posted paper copy; you can print it all or just print one page (several people stick the Diary Page on their fridge door); the Society would save the cost of stamps and paper & ink, and the PDF file can be read by Adobe Reader on a PC or a Mac. Also, future e-newsletters will be in colour. The disadvantages are that, at present, the newsletter is a file of up to 2.5Mb, which means about 15 minutes download time if you are on a dial-up connection. With broadband it only takes a couple of minutes to download. If you do not have an Internet connection then you can't receive it anyway.The other disadvantages are on our side; the editorial/distribution team will have more work to do and we need to change our production methods to reduce the filesize below 1Mb. Please bear with us as we slowly make changes over the next few newsletters. If you would like to receive the e-newsletter instead of the paper copy, please email [email protected] with your name and postcode.

Lundy Island geology – On the left is the Devil's Limekiln; Stand well back! It's steep-sided and deep, with a passage at the bottom where the sea floods in. On the right is The Earthquake, believed to have opened up in 1755 during the Lisbon Earthquake. Photos: Mark Reed

Alright, calm down! Here's some space – now, what was it you wanted to say? Uhhm; er... I can't remember...

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