SABRINA TIMES December 2016

OPEN UNIVERSITY GEOLOGICAL SOCIETY SEVERNSIDE BRANCH

Branch Organisers Report Hello everyone, We had an excellent turn-out for our Day of Lectures on 3rd December at the YMCA Conference Centre in Newport. Everyone who came along enjoyed three excellent speakers on the diverse subjects of modern geophysical survey methods; the exploration of Precambrian oil in Oman; and Lichenometry in Norway. A new subject to many of us, we discovered that Lichenometry is the use of lichen to determine the age of exposed rock, and Hazel Trenbirth described the work done in dating the retreat of Norwegian glaciers using this technique. Peter Brabham described the variety of non-invasive techniques now widely used to build up a picture of what lies beneath the surface of a site requiring a detailed shallow survey. During his fascinating talk on oil exploration in Oman, Neil Frewin mentioned a museum that had recently opened at Kimmeridge in Dorset. It is called The Etches Collection, and it houses a large collection of Jurassic marine fossils discovered in the Kimmeridge Clay by Steve Etches over a 30-year period . The museum also features CGI screens on the ceiling that give visitors the impression of being underwater 150 million years ago in the company of extinct creatures. The Etches Collection is now on my list of places I must visit in 2017! You can explore the website at http://theetchescollection.org/home. If you attended the Day of Lectures, I would welcome any comments (good or bad) about this new venue. In the past we have been fortunate in being able to use a conference room at Cardiff Museum free of charge, which obviously reduces the cost of the event to members, but the Museum wanted to charge us quite a lot this year. Hence we had to shop around for a lower-cost venue, and eventually chose the YMCA Conference Centre in Newport. Perversely, at a very late stage Cardiff Museum decided to waive the hire charge for our AGM in February 2017! but we fully expect the Museum to charge us for future events held there, so any feedback on the Newport venue would be very helpful. Our last field trip of 2016 took place on 16th October in the Beacons, led by Dr John Davies. We were lucky with the weather and, with perfect timing, the sunny day turned to rain half an hour after the trip finished and we were all heading home. A summary of this very interesting and enjoyable trip can be found in the newsletter. I know that many of you will have enjoyed visiting various places both home and abroad during 2016, and will have undoubtedly taken some interesting geology-related photos. So please forget about social media and share your photos with other OUGS members by sending them, together with a few descriptive words, to our newsletter editor John de Caux at [email protected]. As always, any contribution to our newsletter is warmly welcomed!

Finally, I hope to see you at our AGM on Saturday 11th February 2017 at Cardiff Museum, when we will be treated to a “behind the scenes” visit to examine the museum’s mineral collection. With my very best wishes for 2017, Norman Nimmo-Smith P.S. Please don’t forget about the new annual subscription rates – see inside this newsletter for details.

, Inside this issue Field Trip 2

Day of Lectures 7 Philip Clark “Here’s one I made (25 years) Events 12 earlier”

AGM Agenda 12 (see page 4)

Contacts and Editorial 15

D30 Brecon Beacons October 16th 2016

Leader: Dr. John Davies Introduction A group of 17 OUGS members met in the Craig y Fro car park on the north flank of the Brecon Beacons, about 8 miles south-west of Brecon along the A470. In the company of our leader Dr John Davies, president of the South Geological Association, the plan for the day was to explore the Old Red Sandstone (ORS) landscapes at a number of locations in the area.

John has now retired from what was the Countryside Council for Wales. He is chairman of the Welsh Stone Forum and spends much of his time exploring Wales, mapping and co-relating the rocks that he finds.

As shown in Fig. 1, we visited 5 different locations during the day. In John’s words, the day was to be a “coach tour” as we drove from site to site. By doing this he would be able to describe how the landscapes in this part of the Brecon Beacons were a result of its geological history and the different layers of the ORS sediments.

Geological Context The ORS sediments were deposited during early stages of the Caledonian Orogeny, which in this area caused faulting rather than folding. Repeated tectonic movements caused these faults to remain active and large blocks to develop in the landscape (similar to Fig .1 Map showing locations visited in the Brecon Beacons those in Northern England, such as the Alston Block (map reproduced with permission of the Ordnance Survey) that some of us will have become familiar with on Summer Schools). These blocks were separated from each other by positive ridges caused by the major fault zones, in turn causing the sediments to vary in depth from one to another even when the source of the sediments was the same. There is much evidence for the sediments being deposited in various locations in a system of channels developed in a flat landscape.

John’s belief is that, at the time these sediments were being laid down, the region was very similar in nature and size to what can be seen today in the Indus Valley (Fig. 2), with rivers flowing south-west along the south-eastern side of the rising mountain- front. Large amounts of sediment were transported by these meandering and braided river channels spread across the plains. Fluvial fining-upward cycles from sandstones to mudstones can be identified. Away from the main channels, flood-plain deposits include palaeosols with calcretes, and the sequence is followed by two marine incursions of the Upper ORS. Channels frequently commence with coarse bases containing debris eroded from previously deposited palaeosols, followed by massive sandstones and flaggy tops of finer material, passing up into mudstones and calcretes at the top of the cycles. Fig .2 The present-day Indus Valley (image courtesy of BBC)

Naming of ORS rock layers (“stratigraphic nomenclature”)

Many of our text books, and certainly the existing geology maps, all use nomenclature which is out-of-date and John provided us with details of the current names of the official formations, together with an explanation on how the old formations relate to them. The handouts that he provided demonstrate how it is possible to correlate formations right across the Anglo-Welsh basin from south Pembrokeshire in the west to Ross-on-Wye and Blakeney in the east, the sub- groups allowing the details of what were locally named members to be fitted into the big regional picture.

2 Brecon Beacons October 16th 2016 contd.

John’s work has enabled him not only to correlate exposures across the whole of the Anglo-Welsh basin but also to identify additional formations not yet officially named by the ICS (see Note 1, page 6) due to their non-occurrence in Pembrokeshire. These are the Bryn Menyn Mudstone Member; Walford Mudstone Member; and Blaen Haffes Formation, all of which are within the upper half of the Cosheston Subgroup of the Daugleddau Group, previously known as the Brownstones.

Fig. 3 shows John’s revised litho-stratigraphy for the ORS in the Anglo-Welsh basin, along with his new names for three of the units. See also Note 1 (page 6)

Fig 3: A New Litho-Stratigraphy for the Old Red Sandstone of

Location 1 Our journey started at the Craig-y-Fro car park on the A470, where John provided us with his handout and described the plan for the day. From the car park, John pointed out some Quaternary glacial features in the area. A small glacier had formed beneath the crags above the A470 road 11,000 years ago, and the road had been cut through mounds of moraine debris left behind when the ice melted.

Across the road from the car park was a small disused quarry exposing rock of the Senni Formation. A waterfall running down the faces of the quarry kept Fig 4: Craig y Fro Quarry, with interbed- them clean. (Fig. 4). This quarry is a Site of Special Scientific Interest and is the ded sandstone and argillaceous rocks type location for two species of early plants (410Ma) found in the beds of the Senni Formation, namely Gosslingia breconensis Heard and Krithodeophyton Edwards. Apparently David Attenborough visited the quarry whilst filming his “Life on Earth” series, and used dynamite to expose fresh bedding planes in order to find some more plant fossils!

On the north side of the quarry John pointed out a coarse pebble bed of the base of a cycle with finer-grained material lying above it, both of which exhibited cross-stratification (Fig. 5). The pebble bed contained calcrete and mud clasts; the latter had been washed out from the exposed surface to leave numerous holes.

Fig 5: Craig y Fro quarry; pebble bed

3 Brecon Beacons October 16th 2016 contd.

Location 2 We drove a short way along the A470, parking our cars in another layby, where John described the landscape scenery looking north down the Tarrell valley (Fig. 6). In Devonian times we would have seen an upland area in the distance formed by the rising Cambrian Mountains. Erosion of these hills and mountains would have produced the terrestrial sediments of the ORS, with meandering and braided rivers flowing in a south-westerly direction. Running across the lower half of the valley in a NE-SW direction is the Swansea Valley fault zone, which was active during the Caledonian Orogeny and is part of the much larger Welsh Borderland Fault System. On the west side of the valley we could see the crags of Craig y Fro (Fig .7). The upper part of the crags is formed by the Lawrenny Cliff Formation, overlying the Senni Formation. Individual stacks of crags are separated by steep to vertical faults – these were sub-parallel, or branching faults associated with the Swansea Valley fault zone located a short distance to the north.

We then walked a short distance towards the Storey Arms Outdoor Education Centre thence down into the valley along the old military road, [passing a stone wall built by Philip Clark..Ed.] which is now part of the Taff Trail that runs from Cardiff to Brecon. Before doing so, John described more of the ORS “layer cake” strata seen from this point. The famous Plateau Beds form the topmost layer of the hillside to the east, and this unit can also be seen on the summits of and its neighbouring peak Corn Du. These rocks have recently been renamed by the BGS as the Pen y Fan Formation. Below this layer lie the rocks traditionally known as the Brownstones Formation but, as result of his work, John has proposed a new name for this particular unit – the Blaen Haffes Formation. So many new names to remember!

After walking a short distance down the old military road, which can be seen towards the bottom of Fig. 6, we arrived at a pebble bed exposed on the surface of the pathway. This first appearance in the succession of exotic pebbles, including rock and quartz clasts, were matrix-supported (Fig. 8), and John explained that this unit could be matched right across the Anglo- Welsh basin. This was the Lawrenny Cliff Formation, the lowest unit of the previously named Brownstones Formation, and the same bed which appears in waterfalls below the main road in Nant Gerdinen. The suite of clasts it contained showed a Mid-Wales origin.

Fig. 6: Looking north from the A470 at Craig y Fro, with Fig. 7: The crags of Craig y Fro, separated by vertical faults old military road in the foreground

A Break for Lunch at Location 3

It was now time for some lunch, and we drove back down the A470 to the National Park Visitor Centre to make use of its tea-room and toilets. Sitting outside on the terrace in the sunshine we had a lovely view of the two highest peaks in the Brecon Beacons, Pen y Fan and Corn Du. Before heading off to our next destination of the day John described the rock units which could be seen from the National Park Centre, from the Moor Cliffs Formation to the Pen-y-fan Formation. He also mentioned the effect that the fault zone known as the Swansea Valley Disturbance had on the course of the rivers, including the River Wye north-east of Llyswen.

Fig. 8: Pebble bed exposed on the surface

of the old military road, showing quartz and

rock grains

4 Brecon Beacons October 16th 2016 contd.

Location 4 Our journey to location 4 involved interesting driving along narrow roads. Of particular interest were the two steep hairpin bends (known as the Devil’s Elbow) we negotiated as we climbed up out of the Senni Valley. But we all arrived eventually with no mishaps. From here we had a spectacular view northwards along the Senni Valley in the direction of Sennybridge (Fig .9). John pointed out that the Swansea Valley Disturbance (also known as the Cribarth Disturbance by the BGS) ran along the line of the valley, heading in a SW direction towards Craig y Nos, and that the disturbance had controlled the ORS sedimentation. Fig. 9: John describing the landscape looking north

along the Senni Valley At this spot there were a number of rock exposures of the Lawrenny Cliff Formation close to the roadside, and we spent some time examining their features, including exotic pebbles. One of the exposures showed an excellent example of soft sediment deformation (Fig. 10). Before becoming solid rock, the sediment layers had become liquefied and formed cusps, probably in response to being shaken by earthquakes.

Location 5 For our final stop of the day, location 5, we drove a short distance south across the watershed and parked beside the River Llia (Fig. 11), which flows across the New Shipping Formation at this location. Once again John described the near-horizontal layer-cake strata clearly seen in the surrounding hillsides.

The sedimentary layers of the Brecon Beacons nowadays dip gently southwards as a result of compression during the Variscan Orogeny. This dip could be seen quite clearly along the course of the River Llia, where water slides had been created – at these slides, the river flowed downwards across a dipping bedding plane (Fig. 12). Because of the southern dip, the surface rocks become progressively younger along the course of the River Llia. Further south the river leaves the Devonian ORS behind and enters Carboniferous Limestone country. At Porth-yr-ogof it disappears underground into limestone caves for a short distance until it emerges and continues its journey to the sea. (Porth-yr-ogof is well worth a visit!).

Before heading home, we all thanked John for taking us on a fascinating geological journey across a small part of the Brecon Beacons National Park.

Fig 10: Cross-section of sedimentary rock Fig 11: John describing the landscape at location showing soft sediment deformation (top of pen 5, beside the south-flowing River Llia for scale)

Fig 12: “Water slide” on River Llia, where the river flows across a dipping bedding plane (Photo: Linda Fowler) 5 Brecon Beacons October 16th 2016 contd.

Postscript - Maen Llia Standing Stone

As we drove from Location 4 to Location 5 we passed the standing stone of Maen Llia, situated only a short distance from the road (Fig. 13).

Partly moss-covered, this impressive stone is 3.7m high and is believed to date from the . On a clear day it can be seen from quite some distance down the Llia valley, suggesting that it may have been important as a territorial marker. Standing at an altitude of 573m, it is also thought to be the highest standing stone in South Wales.

Like most other standing stones in the Brecon Beacons, this monolith is made of Old Red Sandstone. The information board at the roadside stated that the stone is made from calcrete, although closer examination suggested that it was actually a conglomerate containing clasts of re-deposited calcrete (Fig. 14).

Fig 13: Maen Llia standing stone Fig 14: Close-up of the ORS calcrete conglomer- ate of the Maen Llia standing stone

Note 1: If you are unfamiliar with the International Commission on Stratigraphy (ICS): ‘Its primary objective is to precisely define global units (systems, series, and stages) of the International Chronostratigraphic Chart that, in turn, are the basis for the units (periods, epochs, and age) of the International Geologic Time Scale; thus setting global standards for the fundamental scale for expressing the history of the Earth’. (Source: stratigraphy.org). Many geologists use both the new and old terms interchangeably which can be very confusing!

Report: Norman Nimmo-Smith and Janet Hiscott Photos: Norman Nimmo-Smith, except Fig 12 (Linda Fowler)

6 Day of Lectures December 3rd 2016

Lecture 1 Molecular fossils and exploration at the dawn of life on Earth Dr Neil Frewin BSc (Hons) PhD FGS CGeol

I’d hoped for some time to twist my cousin Neil’s arm to give us a talk. He is an exploration geologist (Global Basins Advisor) for Shell but, like anyone in a high powered job, hard to pin down so I was really pleased, and relieved, when I finally got him to Newport! Working in a commercial environment involves firm guidelines on what can and what can’t be talked about so Neil presented work he had carried out in Oman some years back, updating his presentation with others’ more recent research. He introduced the subject with an overview of hydrocarbon exploration and techniques, and (following a slide of the Kimmeridge Clay, a Neil hydrocarbon reservoir) encouraged us to visit his friend Steve Etches spectacular fossil collection which displays the finds in the context of their ecosystem! He talked about the type of organic matter in rocks that can source hydrocarbons – plants, phyto- and zoo-plankton, bacteria, archaea and how these are converted, first at low temperatures (c 50 °C) to kerogen and bitumen, and then at higher temperatures (around 200 °C) to petroleum, gas and pyrobitumen. Much recent work done to understand the origins of hydrocarbons uses biomarkers (e.g. cholesterol) with techniques like gas chromatography, comparing areas of investigation with modern environments. However, we have very little information about the Early Cambrian bio-record, just after the “Cambrian Explosion” and it is this time that he went on to describe. Neil worked for Petroleum Development Oman (PDO) for almost four years at the end of the 90s and whilst there was able to investigate salt basins in the south and centre of the country. Although

Oman is one of the smaller oil producers, the system in the Cambrian and Precambrian rocks there is significant as it is unusual for salt basins to retain hydrocarbons for so long: in fact these are the world’s oldest known commercial deposits. He worked on their characteristics using C27 sterane which has an unusually negative carbon isotope excursion. The source matured at about 400 Ma but hydrocarbons then had to be retained in a reservoir: This is the importance of salt as a seal though, on the downside, imaging in salt is particularly difficult!. Also, although salt is generally accepted to be a good seal, surprisingly it does absorb some of the hydrocarbon, and it does fracture as well as flowing. (Fig. 1) Neil went on to describe a unique hydrocarbon bearing rock found there, the Athel silicilyte. This dates from the Proterozoic, composed of 80-95% [Figure 1: A piece of drill core showing oil microcrystalline silica, with crystals 2-3 µm in size. Laminae of organic matter seeping into salt from a fracture] alternate with the silica-rich layers and unusually the source rock is also the reservoir. It lies beneath the salt which forms the reservoir seal. Again, he brought an example to show us, encased in a block of Perspex. (Fig. 2) apologies for poor quality, but you should be able to see the laminae]. The Athel basin, lies between two carbonate platforms dating from the time of Gondwana break up. Optimal conditions for formation of silicilyte (anoxia, microbial mat growth, low pH, high silica saturation) were probably reached for a short time during deposition of a highstand systems tract (Rahabi et al, 2014). The laminated silicilyte may have been deposited in a highly stratified water column with chemoautotrophic bacteria as the hydrocarbon source. The water column was probably hypersaline, rich in O2 at the top but in H2•S lower down. Silica would have rained down through the water column to be deposited on the sea bed. The fluids in the Athel field become cleaner with depth and amazingly this is so clean that it has been used in a vehicle engine Fig. 2: Specimen of Athel silicilyte encased straight out of the ground without further refining! in Perspex;

So, Neil concluded, what is the significance of this? Apart from the fact that it is an intrinsically interesting example of a unique oil deposit, one possibility is that it could be found in other planetary environments: John Grotzinger, who worked on this, is currently involved in the Mars Rover programme. I M Al Rajaibi , C Hollis, J H Macquaker. Origin and variability of a terminal Proterozoic primary silica precipitate, Athel Silicilyte, South Oman Salt Basin, Sultanate of Oman. Sedimentology. Oct 2014.

Linda Fowler

7 Day of Lectures December 3rd 2016 (contd.)

Lecture 2 “Near Surface Environmental Geophysics for Site Investigations” Dr Peter Brabham, Senior Lecturer in Applied Geology & Geophysics, Cardiff University Peter started his talk by highlighting the dangers of inadequate subsurface surveys that don’t reveal potential hazards beneath the ground before the start of building projects. Examples include voids beneath a housing development built in a limestone environment; buried structural hazards and contamination beneath brownfield sites; and unexploded ordnance. Site surveys that only employ boreholes to sample the ground at specific points need to apply interpolation between individual boreholes, with the result that important Fig 1: Interpolation between boreholes can lead to subsurface features can go unnoticed, as shown in Fig 1. erroneous results (courtesy of Terra Dat) However, help is at hand - nowadays a range of non-invasive geophysical surveys can be used to accurately measure physical properties of the subsurface, without the need for drilling boreholes or digging trial pits. The data gathered from different types of geophysical measurements can be combined to provide a very detailed picture of what lies beneath the surface, in some cases down to a depth of about 100 metres. Once these initial non-invasive surveys has been carried out and the data analysed, further surveys can be carried out if deemed necessary on a much more limited and selective basis using traditional invasive methods. Geophysical surveys offer advantages such as rapid coverage; no exposure to buried hazards; and minimal (or no) disturbance to the surface. Peter described a number of geophysical techniques that are routinely employed to map the near surface: Microgravity - In microgravity surveying, areas of contrasting density are located by collecting surface measurements of the variation in the Earth’s gravitational field using a gravity meter (Fig 2). The meter is essentially a highly sensitive spring balance that records positive and negative gravity anomalies (also known as Bouger anomalies). Magnetics - The magnetic survey technique is based on mapping localised variations in the Earth’s Fig 2: Gravity meter for measuring magnetic field caused by sub-surface magnetic Fig 3: Fluxgate gradiometer, Bouger anomalies materials, which range from naturally occurring used for measuring minute (courtesy of Scintrex) magnetic minerals to man-made ferrous objects variations in the Earth’s (Fig 3). magnetic field (courtesy of British School at Rome)

Seismology – With this technique, operators measure the travel time of seismic waves that are reflected from, or refracted by, subsurface boundaries (Fig 4). Seismic energy can be provided by an impact source such as a sledgehammer or small explosive charge. Recordings are made of the seismic waves via a linear array of sensors (geophones) on the surface (Fig 5). In practice, seismic reflection surveys don’t work too well in the top 30 metres below ground because of overlapping seismic arrivals, whereas seismic Fig 4: Principle of seismic refraction refraction generally provides better results at shallow depths. (courtesy of Terra Dat)

Ground Resistivity – This survey technique measures variations in the electrical resistivity of the ground across arrays of regularly spaced electrodes. An electrical current is injected into the ground via one pair of electrodes, and the resulting potential field set up beneath the surface is measured by another pair of electrodes. Resistivity data is recorded using complex combinations of current and potential electrode pairs to build up a picture of resistivity beneath the survey line.

Fig 5: Seismic refraction survey using a hammer and 12 geophones (courtesy of University of British Columbia) 8 Day of Lectures December 3rd 2016 (contd.)

A survey result obtained by measuring subsurface electrical resistivity, by means of a linear array of electrodes inserted into the ground, is shown Fig 6. This is a 2D cross-section of a slope prone to landslip, and shows a lobe of mudstone (blue) overriding the sandstone bedrock (red).

Fig 6: Cross-section of slope derived from electrical resistivity measurements (reproduced with the permission of the BGS © NERC. All rights reserved) Fig 7: The principle of ground electromagnetic conductivity for site investigation (courtesy of Peter Brabham)

Ground Conductivity (electromagnetic) - This survey method measures the response of the ground due to the propagation of an electromagnetic wave. (The same principle is used in a “metal detector”). A transmitter coil generates an electromagnetic field which propagates into the subsurface. As the wave travels through the ground, eddy currents are induced in conducting material in the subsurface. These eddy currents then generate a secondary magnetic field which is detected by a receiver coil above ground (Fig 7). The measured response is dependent on the structure of the ground, moisture content and the presence of buried objects. The measuring instrument is normally be carried by hand (Fig 8) or towed by a vehicle. Its performance can be improved by both using a number of different transmission frequencies and increasing the separation between the transmitter and receiver coils.

Ground Penetrating Radar – In this type of survey, a pulsed radar system is moved along a survey line to build up a picture of what lies beneath the ground by detecting radar pulses reflected from subsurface features (Fig 9). The quality of results obtained using ground penetrating radar is very dependent on ground conditions and, for example, is not very effective in Fig 8: Typical setup for ground electromagnetic wet clay, which absorbs the conductivity measurements transmitted signal. (courtesy of Peter Brabham) The measurement data captured using the above techniques is invariably recorded digitally, Fig 9: Ground penetrating and sophisticated processing software can radar in operation (courtesy produce impressive detailed 2D and 3D of University of visualisations of the subsurface. Recorded data Southampton) can be quickly processed in the field using laptop computers. Data from measurement instruments is normally tagged with geolocation information provided by differential-GPS, to sub-metre accuracy. Aerial photographs of the survey site can readily be provided by means of a camera installed on a drone - these have become much more affordable in recent years (Fig 10). As well as producing a 2D aerial view of the site, image processing Fig 10: Drone fitted with camera for aerial photography software can also generate a 3D model of the landscape. (courtesy of HellyTelly)

9 Day of Lectures December 3rd 2016 (contd.)

During his talk, Peter described a number of case studies where he had employed geophysical techniques to survey the subsurface, including landfill sites and river crossings. One case involved imaging an old mineshaft lined with bricks. When baked at high temperatures, bricks become magnetised, so that the mineshaft produced a magnetic anomaly that could be detected by a magnetometer. Any ferrous material dumped in the mineshaft would add to the anomaly. The void space or presence of backfill material in the shaft could also be detected using other techniques such as microgravity and ground conductivity. Another case study Peter described was an electromagnetic ground conductivity survey in the brownfield site of Barry Docks. In its heyday many decades ago, one area of the dockyard contained a large number of oil storage tanks with associ- ated railway lines and sidings. These were subsequently demolished and the dock area turned into a brownfield site filled with all sorts of undesirable industrial materials and pollutants. One of the recent survey plots is shown in Fig 11, alongside an aerial photograph of the same area, taken when the dock was operational. The blue colour in the plot represents high ground conductivity, which can be seen to correlate nicely with the oil tanks and railway lines in the aerial photo, and is un- doubtedly due to the presence of spilt oil now contaminating the ground.

Fig 11: EM ground conductivity survey data compared with aerial photo (courtesy of Peter Brabham

The main message we took away from Peter’s highly illuminating talk was that geophysical survey methods are able to pro- vide detailed subsurface information fairly rapidly for a relatively low cost, without the need for invasive boreholes and trial pits. Advances in technology, particularly in the areas of data processing and 2D/3D visualisation software, now provide geologists with sophisticated tools for non-invasive site surveys. And, by combining datasets obtained using different geo- physical techniques, maximum information about the near surface structure can be produced.

Norman Nimmo-Smith

10 Day of Lectures December 3rd 2016 (contd.)

Lecture 3

The third lecture of the day was after lunch. Hazel Trenbith presented her PhD project entitled “ How can we date the retreat of Glaciers from the last 500 years? Using lichens!" This work came from the Geography department of Swansea University. The supervisor, JA Matthews began collecting data more than 25 years ago from the glacier forelands of southern Norway and a diagram showed the progressive retreat of a glacier since about 1750, dated by known events and the deposition of moraines. Lichenometry was first developed by Roland Beschel in the 1950's measuring diameters on lichens on tombstones in Austria and since then it has been used widely to date rock surfaces. There are two methods : direct and indirect. The indirect method requires the observer to know the age of the substrate on which the lichen is growing. i.e. the tombstone} and then make a correlation between the size of the lichen and the surface age. The direct method measures the growth rate of individual lichens in real time and the construction of a growth curve. In arctic-alpine environments above the tree line lack of suitable organic material makes other dating techniques unsuitable such as dendrochronology, and radiocarbon dating and the wildly expensive cosmogenic nuclide. Crustose lichens grow very slowly and are long lived making them useful to estimate late-Holocene timescales. Basically, if the relationship between the size and age of the lichen is known, then it is possible to infer the age of the surface. In the direct method used by our speaker, 2,795 individuals of the Rhirocarpon subgenus were studied, over a period of 25 years. These were at 4? sites on 18 glacier forelands in southern Norway. The beauty of the method lies in its simplicity. It only requires red marker lines to be painted on the adjacent rock with an ID number and the measurement of the individual across the long axis using a pair of callipers. The mean annual growth rate ranged from 0.43 mm/yr to 0.87 mm/yr. A number of factors affected the growth rate e.g. it declined with increasing surface age, there was a stronger relationship with winter rather than summer temperatures, there was a weak relationship with altitude. Site aspect was influential, with greater growth on SE and SW facing rocks and the angle of the rock was another factor so that there was greater growth on the lower angled rocks. There were many graphs and one in particular showed unusually high growth rate in 1989-90. This was a period when there was more than average precipitation, greater than average mean temperatures and little or no snow cover. The conclusion was that lichenometry is a cheap and easy too] for the dating of surfaces exposed during the last 500 years when radiocarbon dating is least efficient. A further advantage is that lichens are present on many rocky substrates, so that lichenometry is a useful proxy dating method used on its own , or in combination with other methods

Teresa Jenkins

11 Severnside Branch Events

2017 EVENT LEADER DETAILS National Museum of Wales. Cardiff February 11th Branch AGM

Geochemistry and Microscopes February 24/26th Aberystwyth Charlie Bendall WAITING LIST ONLY

The itinerary will include: Penwyllt, Henrhyd Falls, Clun Gwyn Falls, Sgwyd Gwladys, River Nedd Fechan Waterfall Country March 19th Gareth George Copies of both Gareth's books (Sedimentology in South Wales Brecon Beacons & A field guide to South Wales) will be available for sale on the day for a discounted price

Aprll 23rd Lavernock to Penarth Steve Howe

July 2nd Chedworth Paul Olver

Gilwern Hill and Clydach Gorge October 15th Dilys Howell

Branch Annual General Meeting

Open University Geological Society AGM of the Severnside Branch

Oriel Suite National Museum of Wales, Cardiff 11th February 2017 11.00 a.m. AGENDA

Apologies for absence

Matters arising from the minutes of the last meeting held on13th February 2016. (Published in March 2016 edition of Sabrina Times.)

Officers Reports:

Branch Treasurer Branch Organiser Coffee will be served from 10.00 a.m. Other Officers The Branch Library will be available Election of Officers Branch Organiser Branch Treasurer There will be a “behind the scenes” visit Committee members to the museum’s mineral collection in the afternoon Any other business

12 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 know so that he can keep in touch. 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 £2 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)

INCREASE IN MEMBERSHIP SUBSCRIPTION RATES

At the Society AGM, held on 16th April 2016 in Scarborough, the Members voted to increase the membership subscription rates from the 1st January 2017. The increases are: Single membership from £18 (€21) to £22 (€27) Joint membership from £26 (€30) to £32 (€39) Family membership remains unaltered at £2 (€2) MEMBERS ALREADY PAYING BY STANDING ORDER : Now is the time to change your Standing Order, do not leave it till later, you may forget! If you use electronic banking, you can do this on- line or otherwise visit your bank branch. Calculate your new subscription amount Ensure that the payment date is 1st January – not in December, or later in January, and definitely not in February or March (see Note 1 below) Ensure that your membership number (or membership numbers in the case of Joint Members) is in the reference field (see Note 2 below). MEMBERS WHO DO NOT PAY BY STANDING ORDER : Why not take this opportunity to set up a Standing Order? A Standing Order Mandate form is enclosed. If you do not want to set up a Standing Order please remember to make your subscription payment by 31st January (see NOTE 1 below) and ensure that your membership number is quoted (see NOTE 2 below).

Note 1: At the AGM it was proposed that a Constitutional change should be raised at the next AGM (13th May 2017 in Milton Keynes) to change the final subscription renewal date from 31st March to 31st January and that this would come into force in 2018. This would mean that in 2018 any member not renewing by the 31st of January would cease to be a member on that date, and therefore, would not be entitled to a copy of The Proceedings; which is generally sent to the printers in February.

Note 2: The membership number is very important as some subscription payments are made from non-members accounts and the actual members cannot be identified. There have been numerous occasions in the past where this has occurred and it is a lengthy process to identify the member. If you cannot remember your membership number, please contact the Membership Secretary at: [email protected]

Please advise the Membership Secretary of any change to your name, address or email address. This is important because undelivered Newsletters and OUGS Proceeding will not be forwarded at the Societies expense.

13 CLAIM YOUR REFUND FOR THE 2016 SYMPOSIUM

A refund of £16.00 per person is available for all delegates who attended both days (Saturday & Sunday) and £8.00 for those delegates who attended just one day and paid the full daily rate (see Note 1 below). There are 3 options to claim your refund: OPTION 1 – email [email protected] with your bank details and I will pay the refund electronically. OPTION 2 – send a SAE to John Gooch, 32 Church Walk, Euxton, Chorley, Lancashire, PR7 6HL and I will send you a cheque for the refund. OPTION 3 – email [email protected] with you name and address – however, £1.00 will be deducted from the refund cheque to cover postage and stationery. If you do not wish to claim your refund – do nothing Note 1. The shared costs (lecture theatre, speaker’s costs, coach hire, etc.) for a Symposium are calculated and then divided between the delegates. As the number of delegates is not known in advance the numbers from previous symposia are used as a guide. However, Exeter Symposium was such a great success that many more members attended than was originally envisaged, thus the shared costs per person were less than the amount charged, therefore, a refund is available. Any monies not claimed by 31st January 2017 will be passed onto the 2017 Symposium. John Gooch Society Treasurer

Some holiday photos - by Philip Clark

Pillow Lavas - Oamaru - South Island New Zealand Oligocene Sediments in Provence

Do any readers have interesting holiday photos that could fill blank spaces in future issues of Sabrina Times ?

14 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: Janet Hiscott 01633 960845

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 still receiving Sabrina Times by post why not get the much better colour version of this and future issues of this 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 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. For large files OneDrive or Dropbox may be used.

MERRY CHRISTMAS AND A HAPPY NEW YEAR TO ALL OUR READERS

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