Geo-Amble 14th August 2017

HERE is a geology map of the area and notes on the formations

We parked near Ham Bridge at the entrance to the driveway leading to Ham Mill and Ham Farm.  Along the way to the small quarry that was our destination we noted the very steep hillside we assumed cut into by the River Teme and obviously of a more substantial make up than the flat river valley.  According to the geology map this is Raglan Mudstone territory, the lumps of rock we found along the way being a type of fine sandstone, often found within the softer mudstones.  The geology map of the area does not however show these sandstones hereabouts so seems to be somewhat in error.  I stopped the group to show a distinct hollow way, leading up the steep, grassy hillside away from the river and a local crossing point.  I have always taken this to be a drover’s trail created by centuries of passing herds. Further on a very disturbed area, shown on the map as a quarry, the question being for what?  Possibly mudstone for bricks as no rocks visible (although the Building Stones database states it is St Maughans, that is wrong). Scattered about in the grass around here we discovered several giant puffballs and the group volunteered that I should take home the largest and eat it myself.  Writing this from my hospital bed I can tell you that fried in butter with garlic and olive oil it was like eating marshmallow, not unpleasant with quality bacon and a fried egg, but not a repast I am likely with much enthusiasm, to re-eat. As we approached Ham Farm we noted buildings, some very ripe for refurbishment, made from cut stone, with brick infill and timber frames.  Through the farmyard on the right of way, it was a short walk up to the small sandstone quarry and the source of these stones we were sure.

Although the Building Stones database again states that this sandstone is St Maughans formation from the Devonian period it cannot be, as it is far below the Bishops Frome nodular limestone which itself lies under the St Maughans. I sought direction from a noted geologist and she tells me it is definitely in the Raglan sequence, being the sandstone referred to above and obviously in sufficient quantity for it to have been used in the local farm buildings.

The quarry face showed clear signs of bedding at odds with the mainly horizontal layers.  GEO AMBLE 14AUG17 (7)First thoughts were that this is an example of ‘cross’ bedding and I for one have never really grasped what that is all about. For those of you who like me struggle with simple things here are some notes. If sediments are laid down without disturbance (I am thinking underwater for this) then they will form a smooth layer over the underwater ground surface.  Stops and starts in the deposition and/or changes in particle size, will show as joints (see below).  If water flows across this submerged layer, then the particles will tend to be moved along dependent on the speed of the current and the particle size. We have all seen ripples in beach sand and these form under flow conditions. Exactly why they form is not fully understood (I am pleased to report, HERE is more information) but they do. As ripples develop, particles are driven up the shallow slope that faces upstream, reach the top then tumble down the other side, which is steeper. This occurs whether water or air (wind) is the driving force and in air the ripples are usually much larger.

Because the particles vary in size and density, given their origin from (possibly many) different types of rocks upstream, they do form distinct, albeit thin, layers.  If the ripples are preserved by subsequent deluges bringing  more material down and burying them, then eventually rock is formed and the ripples are retained and visible if the rock is cut into.  HERE is an animation that might help.

The other process in operation within, especially, braided rivers, is where channels move around in the bed of the river, cutting through existing deposits (themselves ‘bedded’) and creating new ones on the inside of bends and so on as flow rates vary. You can imagine that this can leave a very confused set of beds built up over time as illustrated below.  It is possible to see these paleo-channels in rock exposures, certainly at the Nubbins and here too I reckon.

braided river 3d levels

Sedimentary deposits act as a geological tape recorder (I remember those); they record the activity of the local environment and in the quarry we looked at this would have been a river.  If there is a change in the process, for example increased flow (and therefore carrying energy) putting down bigger particles, then the layers will show this, sometimes very subtly.  The layers are separated by bedding planes and these tell us that deposition stopped. In effect this is a gap in the record that could last from minutes to thousands of years. Moderate i.e. thick beds, such as we saw at the quarry in the lower sections, tell us that deposition continued in the same way for a very long time with little disturbance. Higher up, and quite abruptly, the beds became much thinner indicating a more disturbed environment.  What could this have been?  Climate change leading to increased flow?  End of the Silurian and start of the Devonian–continents colliding?  Ideas on a post card please. A more lengthy explanation is to be found HERE.

Members Evening June 1st 15

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, map of Arouca locationa 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 rockIMG_0706 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.

Busk Coppice and Quarry Hill

St Mary's, Stanford with Orleton, looking South

St Mary’s, Stanford with Orleton, looking South

Under the Spreading Chestnut tree

Under the Spreading Chestnut tree

On Thursday February 14th, having opened all our cards and under grey skies, Ian, Mike and self, continued our foray into the Teme Valley and you know, sounds daft, but it really does feel like exploration when for us, checking out the rocks is a novel experience.  Anyway, we headed first to St Marys, Stanford, to see if we could find on the ground evidence of the mapped Raglan Sandstones in the land above the church. At the spot under a spreading chestnut tree we did indeed find sandstone rocks but these were scattered about and could possibly have been from local building works although at the time we preferred not to see them that way. To us they seemed similar to the church and to local walls of the old rectory just across the road.

Sandstone from West of St Mary's

Sandstone from West of St Mary’s

Sandstone from West of St Mary's

Sandstone from West of St Mary’s

 

 

 

 

 

 

Travelling up the road by car, we entered Busk Coppice to show Mike the large quarry found on our last visit—did this supply the stone to St Marys’ Stanford, but where is the lime kiln that Mr Churchill the farmer had told us about?

Lime Kiln in Busk Coppice

Lime Kiln in Busk Coppice

Lime Kiln Busk Coppice

Lime Kiln Busk Coppice

We wandered about down into gullies keeping in mind that it would not be far from the Bishops Frome layer, here underlying the quarried rock, St Maughans sandstone.  We gave up and called the farmer who directed us back up the track to a shooting platform and

Conical Kiln in the Undergrowth

Conical Kiln in the Undergrowth

 

Sketch of Lime Kiln, Busk Coppice

Sketch of Lime Kiln, Busk Coppice

goodness, there, not 3 metres from the trail, was a deep conical brick lined pit, a danger to anyone not seeing it, set in a levelled off terrace.  On the terrace below was a substantial brick built arched construction leading into the terrace and under the cone. A magnificent example of an ancient kiln, a little the worse for wear and needing attention to remove trees and soil but other than that looked like it could be relit straight away. This would have been used to make lime for mortar for building and for the fields and was slap bang into the Bishops Frome limestone, the calcrete (fossilised soil) referred to in other posts. According to Mr Churchill, a farm worker by the name of Tommy Tucker used to live in the arched kiln.  A little archaeological investigation sounds in order. Read Nils Wilkes fascinating study of Lime Kilns in Worcestershire HERE

So you burn limestone at 900C thus converting it from Calcium Carbonate to Quicklime and Carbon Dioxide, then you slake it with water making Calcium Hydroxide, known as lime putty, used as the base for a slow setting, traditional mortar still used in renovation work today.

That accomplished we went by car along the charming, twisty, switchback lane to just beyond Orleton until we reached the foot of Quarry Hill—the clue being in the name.

Valley Geological Map from BGS

Valley Geological Map from BGS, click to enlarge

This is an outlier from the main escarpment.  The geological maps show the limestone outcropping around the whole of the Bromyard plateau, with an island of it on top of Quarry Hill.

According to the maps the limestone was set in a sea of (Silurian) Raglan Mudstone only, and as we struggled up the wooded precipitous hillside littered with fallen trees, the redness of the soil seemed to indicate that this was the case.  There were occasional obvious trackways contouring the slopes, signs of forestry work or perhaps quarrying, who knows?  In the red roots of fallen trees we searched for stone as tell-tale of underlying rock and these at first were typical of Raglan sandstone.  Continuing to force our way upwards to the very top we discovered a substantial area clearly shaped by human endeavour.  There were no rock faces but the humps and bumps seemed to show that much of the top layer of limestone had been removed.  We did uncover large stones set in a semi-circle, perhaps the foundation of a kiln?

Conglomerate, both ruddy and grey with bedrock behind

Conglomerate, both ruddy and grey with bedrock behind

Just down the slope, we chanced upon exposed bedrock and took samples.  To our surprise these mirrored an earlier finding some way down the slope (that we had tried to ignore), of a coarse conglomerate, not what we expected at all.  One was ruddy, the other light grey, found 3-400mm above one another in clear layers.  The map shows (Devonian) St Maughans conglomerate in a number of places, but nowhere near this spot, and certainly none below the limestone. So how to explain this?  We retrieved our samples, cleaned them and will set them before the oracle as soon as we can.

Conglomerate

Conglomerate

Top of Quarry Hill, Mike on Access Trackway

Top of Quarry Hill, Mike on Access Trackway

Teme Valley around Stanford

Teme Valley around Stanford

Searching for ORS Quarries

The above acronym was useful for one thing, it allowed me to fit the title all on one line, but they are not helpful to use unless in very common parlance.

Old Red Sandstone (mainly Devonian) forms the bulk of what we from Martley see across the Teme.  There is no Devonian in Martley but there are one or two buildings, most notably the Old School by the Church, made from a grey/green sandstone (one wonders if geologists have hyper eyesight at times) that certainly does not occur locally.  Travel to Clifton and especially Bromyard and many buildings are from the same material, so what is it?  Years have gone by and no answer to this, one would have thought simple, question was found in spite of 3 or 4 geologists being asked their opinion.  So, we made our own decision by concluding the flippin’ obvious–St Maughans Formation–has to be, indeed is.

Our interview last week with John Lane suggested three quarry sites near Stanford and this Sunday, Mike, Jane, Colin and self had a fabulous walk in brilliant, sunny but cold weather, tramping the dingles and hills near Park Farm, Stanford Court and Stanford Church. Where the land slopes steeply from the Bromyard plateau down to the Teme Valley it is heavily wooded, a tangled and often impenetrable jungle with access ways for those who rear pheasants and remove timber.  There is a good rights of way network too and the signage not bad given the remote location.

We reckon we found the site of one St Maughans quarry (there are two more to investigate but we ran out of time).  There was a pretty little spring rising in a small cave under massive, bedded sandstone and being winter the best time to observe rocks that in summer will be well covered up.

Just around the corner from the quarry we came across the fabled Temple of Temple dingle (GR SO370253 264721), a place both Mike and I had long heard of but never been able to find.  There it was, at the side of a very good track, terribly ruined but showing its obvious former splendour. Who built it?  When? How long was it occupied?  Many questions and will attempt to find answers–some of you may know, if so please would you contact me, thanks?

Pictures:

  • Tangled Woodland Tangled Woodland
  • The Temple West Front The Temple West Front
  • The Temple South East The Temple South East
  • The Temple East Side The Temple East Side Outer wall this end has collapsed
  • The Temple from the North The Temple from the North
  • The Temple and Retaining Wall The Temple and Retaining Wall
  • Is this a Quarry Site? Is this a Quarry Site?
  • or this? or this?
  • Pretty Cave with Spring Pretty Cave with Spring
  • Access Tracks--Very Muddy! Access Tracks--Very Muddy!
  • Spring with St Maughans Spring with St Maughans
  • St Maughans St Maughans