The first members’ evening that we have held and it was a success, so will repeat. Relaxed atmosphere, smorgasbord of topics, short, illustrated presentations and free, yes free, cheese, crisps, biscuits and a glass of wine.
First we heard from David, Ingrid and John a totally non-technical account of their recent visit to Arouca, a geopark in northern Portugal, where good contacts with the geopark team were made and some of the exceptionally well presented sites visited. Arouca with substantial European and regional Portuguese funding is developing an envied park, conserving and celebrating local geology and with it amplifying trades and crafts that would otherwise probably die out. Similar but on a larger scale to our plans for the Teme Valley. Bordering communities eye the project and make noises as to how they can join in but we understood that this is not really part of Arouca’s plan. Famous firstly for the giant trilobite fossils mentioned in Prof. Richard Fortey’s book, ‘Survivors’, of equal international status is the small area of nodular granite–known in Portuguese as the rocks that give birth (Pedras Parideiras). The process of their formation is not really understood, but basically within a matrix of granite in an area no larger than 1 square kilometre, many millions of black ellipsoid nodules are to be found. Owing, it is believed, to the differential expansion of the light coloured granite and the dark nodules, the ellipsoids gradually release from the parent rock and appear loose on the surface. One can only imagine the mystery of this in the minds of a rural and uneducated populace. The general bedrock of the Arouca Geopark is granite along with Ordovician Slates but on THIS site there is a much more detailed description. The countryside is rugged, provides excellent walking on well marked trails and abounds in drifts of colourful wild flowers.
During our stay, David had one or two personal adventures that left Ingrid and me scratching our heads. The more costly was the loss of his wallet with credit cards, driving licence and around £90. Tracing it in English by telephone to Portugal was tricky. Its ultimate fate, destruction at the hands of those who serve us–i.e. the British Consul and team, convinced us once again that the expectation of help from our overseas officers is a triumph of hope over experience. Pictures (on external site, click down arrow on right and select slideshow)
Second up were free cheeses and bikkies plus a glass or two of wine and time to look at small displays set up by Georgia with her wonderful textiles and books, Arouca with maps, books and rocks and such colourful minerals from Margaret–thanks all.
Ian (Fairchild) related the tale of fairly intrepid exploration into one of the dingles in the Teme valley at Stanford. A good friend Robin Dean (churchwarden of St Marys Stanford) owns around 20 acres of what is now VERY rough ground but was, in the old days, an orchard (it seems). Robin should really get his mower out.
The challenge in pouring rain, was to walk up the bed of Fall Dingle to one of its waterfalls, checking out rocks and plants on the way. Bits of tufa had been seen and Bishops Frome too, as well as substantial blocks of Raglan Sandstone and softer mudstone, chiselled out by the stream, innocent enough on the day but fearful in flood judging by the massive trees lodged in the bed. En-route we noticed seepages building tufa on the banks of the stream, clear indication that the limey nodules of the Bishops Frome (aka Psammosteus) limestone top member of the Silurian (Raglan) were close by but higher up the hill. A previous blog told of the lime kiln built into the limestone not far from the stream that we were exploring. Half an hour of clambering brought us to a surprising and impressive cleft with water tumbling over its lip in a double drop and a fine tufa fan encased in liverwort descending its face. So rugged the ground and obscured by trees and dense vegetation that surely few reach this spot. A much more direct route back through carpets of wild garlic, to the warmth and hospitality of Robin and Lesley’s house, rounded off a memorable morning. Thanks to Robin and Lesley for their as always warm welcome.
Surely a highlight of the evening and a marker for years to come were the three rock sample display cabinets designed and made by member Ian Pennell (of Scar Cottage the magnificent Bromsgrove Sandstone quarry garden in the village). Since retiring, Ian has submerged himself in a number of practical pursuits and his cabinet making talents were harnessed to produce these very fine items from Yellowwood, a hard, much sought after South African pine. A little ceremony of unveiling took place with a short speech of thanks from David and a round of applause. Well done and thanks Ian! A day out is set for July 11th 10am at Crown Martley–come along if you can. The ideas is to plan a route, then go out to collect, ultimately, samples of all of the formations from the surrounding area. Last count suggested there are over 20, so doubt the job will be done in one go.
Georgia, with her very obvious affection for the Lizard in South Western Cornwall, so fond is she that she had written a song that she performed for us accompanied on her guitar–yet another talent of this talented lady! Georgia knows the Lizard as well as anyone, particularly the exceptionally varied and in places very rare geology, a slice through a section of ocean crust, including the upper level of the mantle, thrust onto continental crust. One immediately realises that a field trip-would have to be at least for a weekend–and beckons strongly, a fascinating area with Georgia as number 1 choice for leader and guide.
These blogs are written as a record of TVGS activities. That is important. I personally have absolutely no desire to reserve this space for myself, other contributors are most welcome. Having said that I also want to say what a journey this geology thing is becoming. Who would have thought a few years ago, in 2010, after a dig at Martley Rock, that we would be drawn into a new pastime of endless fascination? Who would have thought that this odyssey would take us to the Houses of Parliament, to France, to the Teme valley in company of academics, to listen, spell bound to great speakers, some even from our own community? Me? You must be joking. Many of us feel this way. We often quip that our society only wheels out real geologists when we need them. Believe me we so appreciate the time you freely give us, all of you. It is such a great privilege to learn about this science, to wonder at the life a pebble has led, to look at our landscape with new eyes, to start to interprete it, and to consider the unimaginable years that have passed to leave it in the brief state that we see now.
For us there are new adventures nearly every day, Monday (19th Jan 2015) the science of volcanoes, yesterday (22nd) extreme tufaring (my word) in the Teme Valley, tomorrow a meeting with an old man who can relate the story of the valley, of its quarries, occupants and history. We are particularly keen to find out more about where the stone for Shelsey Walsh Church and the cottage nearby was quarried, what happened at Southstone, that great crag of tufa, perhaps the largest in the country with its sacred spring, vanished chapel and hermitage.
Our field scramble yesterday in the company of Professor Ian Fairchild and with Hannah Townley of Natural England, led us to parts of the west Teme jungle I doubt few have ever been. A spider’s web of fallen trees, exposed roots, brambles, muddy slides, precipitous slopes, waterfalls, ferns and creepers. Oh, and tufa! The valley abounds in it. These days largely covered in vegetation, except at grand Southstone or where a fallen tree lies, its net of roots upended to reveal the underlying rocks and earth, characteristically orange with tufa. As I understand it, rain falls on the Bromyard plateau, dissolving particles of calcium carbonate found within the matrix of Devonian St Maughans formation, itself marked by varying deposits of Bishops Frome limestone, a fossilized soil or calcrete. This can be seen as a marked horizon all along the valley in the form of a layer of noduley limey lumps up to 3 m thick in places, usually well hidden with vegetation but appearing where, for example, small land slips occur. At the impervious underlying Silurian Raglan mudstone contact, springs erupt, at Southstone gushingly so, saturated with dissolved carbonate, releasing carbon dioxide as the water reaches the surface. Not much more of a prompt is needed–perhaps a drop down a slope, to pass a tipping point so that the saturated water starts to deposit its load of carbonate. Particular varieties of moss like this water and grow abundantly, but one suspects briefly, to be encased in the lime, petrified on the spot. This process seems to have continued since the last ice age though deposition rates, Ian said, must have declined. Dates from the base of the deposit are from around 7000 years ago. Southstone is a unique site, a site of great value and heritage with a social and recent geological history and should be conserved. Here are a few pictures (by Mike Install). There will be more…..
Looking Down Shelsley Walsh track from the S Bends
At the S Bend-Mike Install, Prof. Ian Fairchild and Hannah Townley
Hard Going
Rough Ground but Tufa beneath
Stream by the S Bends at Shelsley Walsh
Over hanging Tufa in the small stream at Shelsley Walsh
Tufa Waterfall at Shelsley Walsh
Tufa Waterfall at Shelsley Walsh
On the way to Southstone
Tufa on the way up to Southstone, well below the main crag
We stayed with our plans to hold a field trip in May, on 26th and so pleased we did—a very special time together, led by Donnie (Prof. Donnie Hutton), around three local (to Martley) geology sites. The weather was wonderful (seems long time ago as I write this; actually, it IS a long time ago) and for a number of us the day was made extra special by the sight of a beautiful red kite floating along the Nubbins outcrop for 15 or 20 minutes whilst we gathered at Martley Hall in the morning. I have said elsewhere that for twenty years I have scanned the skies in vain and never seen a kite here (other have) until 26th May.
Here is Ian’s contribution (thanks Ian)
Penny Hill, Martley–first, the group drove to examine the Silurian ‘Wenlock’ limestone ridge which forms Penny Hill just north of the village. Accompanied by the landowner, Trevor Nott, and family, we were able to see how the stone which forms the hill is sheared off to the East along the East Malvern Fault. To the east, the wide rift valley of the Worcester Basin, later backfilled with riverine Triassic Bromsgrove sandstone and overlying marl deposits in a dramatic demonstration of the borderline between “old” and “young” Britain and the power of erosion.
The Wenlock limestone is rich in fossils (bioclastic) and formed in shallow coastal waters 423-428 million years ago south of the equator. At this time, most of proto-Britain was part of the micro continent Avalonia, drifting towards the modern day North American landmass of Laurentia through the closing of the Iapetus Ocean.
Iapetus Ocean and Avalonia
The resulting collision attached a piece of Laurentia to the north of us, forming the northern half of Scotland, and may have produced the Malvern fault system during the Caledonian orogeny (mountain building period), setting off the formation of the rift valley of the Severn.
The fossils – no dinosaurs of course, they came hundreds of millions of years later–are predominantly small seabed dwelling creatures; corals, brachiopods (shellfish),
Silurian Fossils
stromatoporoids, crinoids and trilobites, although none of the latter were seen. They are embedded in a grey-blue flaggy limestone with alternating stone, thin mudstone interbed layers and evidence of volcanic eruptions in the form of weathered ash (bentonite) layers. Currently these layers throughout the whole of the country’s Wenlock distribution, are being microscopically investigated by Dr David Ray. We hope he will become a visiting speaker to TVGS.
Fast forwarding 125 million years to the echoes of the mountain building caused by the distant collision of Africa and Eurasia (the Variscan orogeny), our land mass was now drifting through the lush green equatorial region during the carboniferous era, laying down coal deposits across the Midlands, including small patches in Martley. It was probably these tectonic forces which pushed up the previously flat Welsh Marches limestone of which Penny and Abberley Hills are an important part, to form the folded landscape we see today. Note: the profile of Penny Hill has now been recreated following quarrying and refuse landfill. The refuse was capped with clay, extracted mainly from Cob House Fisheries to leave behind many new fishing pools, allowing the controlled capture of biogenic methane. This is used as a fuel for electrical generators on site at Penny Hill to produce electricity for the National Grid, enough for a significant proportion of the energy demand of Martley Parish. Here a few pictures from Penny Hill
After a thorough look around Penny Hill, completing the circuit from the north, around the west, then east and back to our start, we drive over to Brockhill Court where we made our acquaintance with Sir Anthony Winnington, who was doing a bit of gardening, and who most graciously allowed us to see the fascinating geology that exists on his land, adjacent to the house.
Here is Bryan’s report (thanks Bryan)
Brockhill Dyke, Shelsley Beauchamp, where a teschenite dyke is exposed in an old pit. Little remains of the dyke except high up in the eastern end of the pit. However, good fresh specimens of the rock were obtained after a stiff scramble halfway up the face. Sodium rich, it belongs to the syeno-gabbro suite of rocks. It’s mineral composition is very similar to gabbro but the inclusion of an alkaline mineral, (either nepheline or analcite – in this case analcite) distinguishes it from gabbro. Plagioclase feldspar, clinopyroxene, analacite (easily distinguishable), minor amphibolites and biotite make up this medium- grained basic rock. The dyke extends east-west for about 1200 metres and is exposed in small pits on the western side of the Teme. The river itself runs along the line of the dyke until it finds a way through, just below Brockhill Court. Emplaced in the Downton Series of red marls and sandstones it is about ten metres wide and dips almost vertically. No in situ examination of the margins was possible but the Droitwich Memoire has it that narrow doleritic edges to the dyke can be seen. Loose specimens were found of what may have been a fine grained rock from the chilled margin of the dyke. Excellent examples of spheroidal (onion) weathering can be found in the debris of the pit and on the exposed face.
The country rock, marls, silts and sandstones, were ‘baked’ by the hot (1600 degrees C?) magma. The sandstones and are now hornfels, a very hard, metamorphic rock. During the baking some layers of the purple marls were sufficiently plastic to allow the escape of volatile gases and the development of vesicles and tubes which were later lined with calcite, chlorite and analcite. Extreme baking produced vitrified black specimens with conchoidal fracturing. Good examples of all of these rocks can be found in the garden walls of the nearby Brockhill Court.
An explanation of the cause of the Brockhill dyke was given by our very knowledgeable guide, Prof Donny Hutton. The dyke is one of a suite of dykes emplaced in late Carboniferous times (300 Ma) during the Variscan Orogeny. Similar dykes with similar E-W orientation can be found inNorthern Englandand the Midland Valley of Scotland. Variscan subduction with consequent loading and downbending of the lithosphere induced ‘flexural bulging’ with uplift and tensional fracturing of the crust. Low degrees of adiabatic melting produced buoyant syeno-gabbros which rose and pushed into the fractures. Some pictures:
Parking at Brockhill Court
Donny and his Clipboard
Lunch Break
Samples showing Gas Vents
Wall at Brocklhill with excellent examples of all the rocks types
Donny also gave us a very useful rule of thumb for distinguishing between sandstones, siltstones and mudstones. If we can, with the naked eye, see individual crystals and can feel them, then it’s a sandstone; if we can’t see the crystals but can feel them, then it’s a siltstone; and if we can neither see nor feel the crystals, then it’s a mudstone or shale.
Southstone Rock, Teme Valley–to round off the day, a sensational walk up the western slope of the Teme valley to see what is reputed to be the largest tufa deposit in the country, known as Southstone Rock and still, visibly, growing. Originally the site of a hermitage and a homestead, there is no habitation there now (to see an aerial photo before trees, check out Cliff Barnards book, A Tale of Two Villages, ISBN: 0952657503), but the sacred spring keeps working, gushing fulsomely out of the base of the Bishops Frome limestone, laden with calcium carbonate that precipitates in the cooler air. The moss, Palustriella Commutata, seems to enjoy ‘taking the water’ and grows abundantly, being petrified in the process thus creating an easy to work, warm, light but durable building material. This has been quarried for centuries, witness Shelsley Walsh church and nearby cottage, the Lion at Clifton and many other premises, but peculiarly it is difficult to see evidence of this at the site itself. EHT have produced an excellent leaflet ‘Southstone Rock’ Geology and Landscape Trail Guide and these are freely available from EHT (01905 885184).
Here is Ingrid’s report on this part of the day (thanks Ingrid)
On Saturday 26th May (one of the last days of summer 2012) TVGS arrived at the final stop of the Teme Valley Tour. Several of us had never been here and, as promised by those in the know, it certainly proved to be one of the best kept secret places in the area.
After some manoeuvring we somehow managed to fit all the cars safely into a lay by at the side of the road opposite the track up to Southstone Rock. A short trek along a lush and overgrown path and a steep climb steeply upwards. Round a bend and across a rickety bridge and there it was! Best described as a cross between Gormenghast, pumice stone and Lord of the Rings this great white edifice towered above us. The newbies amongst us sunk onto the nearest rock in the shade underneath to catch our breath. We rapidly moved when Donny informed us that it was a little fragile with a tendency to move chunks of itself downwards into the stream below, and no, not pumice at all but the miraculous Tufa rock. Literally a ‘living rock’ and this is one of the best examples in the country. Moving smartly from under the overhang in case of falling boulders, we climbed upwards through a series of secret paths and labyrinthine ways to reach the top.
This was a significant area of pilgrimage in years gone and was said to be inhabited by a hermit. Latterly a cottage was built at the top, but little remains of this and this quiet wooded area was sadly decimated by developers a few years ago, who clear felled leaving all manner of brash and rubbish that nature is slowly healing. The densely wooded hill rose steeply above us but we headed to the shady outlet of a strong fresh water spring – very refreshing on a hot afternoon. From there we followed the narrow stream a little way downhill to see a miracle-tufa rock in production-as the clear water flowed over mosses, slowly petrifying them as it tumbled over a most picturesque water fall to the valley below.
It wouldn’t be a TVGS field trip if we didn’t have a bit of scrambling, duly paying homage in the time honoured way of all pilgrims, we wetted our feet climbing up the stream bed from the bottom to see this more closely. Down below us Donny diverted some of the party by finding playdoh, sorry volcanic clays, apparently top quality potting clays, in the base of the stream near the rickety bridge. It was time to make our way soggily down the hill through the heat of an English summer day, a perfect end to a thoroughly interesting day.
donny at the Base of Southstone Rock
Site of the Old House
Tasting the Water
The Spring
Top of the Waterfall down the Rock
Moss and Petrification creating small tunnels
A new delta forming over and above the adjacent stream
The waterfall unfortunately obstructed by fallen trees nowadays
