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.

A New Trail?

Martley has three geological trails, none to the South.  Ian proposed that a walking route written in the 90s by Keith and Audrey Trumper (who started the Path-or-Nones footpath maintenance group, still going) would form the basis of a geology trail that crossed formations with excellent views useful for interpretation.

On Saturday 22nd March, four of us had a close look at the area; Natalie Watkins provided the professional input, the rest of us tagged along, making what we thought were useful comments.

If the trail IS to come to fruition then funding will be required for art and design, printing and so on; David is looking into this.  The route veers from the original walking route (No 9 if you are interested, see it HERE on the PONS web site) and is not yet settled but will be around 6 miles and is hilly.  The formations crossed, or nearby, are Bromsgrove Sandstone and Sidmouth Mudstone (Triassic), Haffield Breccia (Permian), Highley Fmn (Carboniferous), Wyche Fmn, Wenlock, Raglan Mudstone (Silurian) and good views through the Teme gap by Osebury Rock and of the Bromyard Plateau (Devonian).  We spent time scrabbling about in some of the many quarries on Ankerdine, now deep in a mixed woodland, and from which several local buildings have been made. These include most of the old church, though there are other materials from whence we know not where. Incidentally the church is undergoing conversion to a dwelling and we were kindly allowed to look around by the builder.  Capturing our attention too, the wheel of the apple press by the Talbot (see pic) is a coarse version of, we concluded, the local Wyche Fmn.  In our travels we collected samples of Wyche and the variation was instructive in itself, from fine silty material to coarse, gravelly, proving the existence of different environments all those years ago (+-420Ma) in the early Silurian.

Finally we were kindly entertained to tea and sweet things by always welcoming Nigel and Sarah in their delightful cottage, uniquely placed on the East Malvern Fault, with Silurian, Permian and Triassic in their back garden.

  • Apple Press by Talbot Apple Press by Talbot
  • Apple Press, Assumed Wyche, Very Pebbly Apple Press, Assumed Wyche, Very Pebbly
  • Doddenham Church Conversion Kitchen Doddenham Church Conversion Kitchen
  • Wyche--SIlty, Fine Grained Wyche--SIlty, Fine Grained
  • Wyche Moderately Coarse Wyche Moderately Coarse
  • Wyche Coarse Wyche Coarse
  • Wyche Almost Pebbly Wyche Almost Pebbly
  • Nat in Quarry, Top of Ankerdine, Close to Wenlock Junction Nat in Quarry, Top of Ankerdine, Close to Wenlock Junction

Building Stones news

The Building Stones Project – 1000 Years of Building with Stone – is the latest project run by the Earth Heritage Trust, based at the University of Worcester. It is a 3½ year Lottery funded community history project aiming to investigate the wealth of stone buildings in the 2 counties, and linking them to the quarries which yielded the stone used to build them.

Much information about vernacular buildings and local small quarries is not yet known or is in danger of being lost. This project hopes to learn about the buildings, the people who owned and occupied them, who obtained the stone (and how), the people employed in the quarries, how it was transported, and how far, and other information which will put together a comprehensive picture of stone and its place in local communities and the built landscape.

It is based around volunteers who will be trained to gather information about the stone buildings in their local area, online, on the ground, in the archives, and in discussion with local people.

There is an obvious link to this project with the TVGS, and we have formed a local group to focus on the Teme Valley, initially in Martley and surrounding parishes and hopefully extending further up and down the valley as we develop our working methods and linking with any other groups who may form within the project.

The nucleus of the Teme Valley group has met to look at the scope of the work and how to take it forward, and we now need as many others who are interested to join the group and take part in this exciting opportunity. Already we have identified many stone buildings in Martley which we didn’t realise were there and are beginning to assemble a comprehensive list.

If you are interested in any of the following activities:

  •  Map surveys
  • Photographing buildings

  • Learning how to use archives

  • Online research

  • Asking people about the history of their buildings and local quarries

  • Assisting in technical/scientific stone analysis

  • Data collection and collation

please contact me, on ianpennell1@tiscali.co.uk for more information on how to volunteer, or building.stones@worc.ac.uk for more background on the project.

You can follow the project blog at http://lostquarries.wordpress.com/ , or on Twitter via @BuildingStones.