Geo-Amble 29th August 2017


T’was a darkening afternoon as we tramped along the bridle path, greeting Robin and Leslie Dean at their Hansel and Gretel house before plunging into the wildwood that surrounds Fall Dingle. Apparently cultivated with fruit trees years ago, a site for springs feeding isolated houses with fresh water, a tangled web of fallen trees, brambles and creepers has obliterated, to all but the most skilled of observers, any trace at all of those days.  I am very thankful to Jon and Tom Pearsall for clearing our route the day before.

The way to the fall traversed not only tricky ground underfoot but also of geological interest, a very muddy tufa seep from a spring a few yards up hill.  The incidence of limey Bishops From calcrete much higher up is well known and observed, we guessed that the seep draws its lime through subterranean channels from that arena.  Anything in the path of the seep was coated with a light beige tufa.  We wondered at the purpose of the small human made pool catching the seep water with drain to the nearby stream.  At the fall itself, an impressive and unexpected sight, evidencing fierce flood flows though only remnant at the time of our visit, we inspected rocks in the bed, noting slabs of the local sandstone (Raglan) and more rarely, nodules of Bishops Frome.  An exciting adventure awaits to inspect the stream bed above the falls and locate where it transits from the Devonian St Maughans, over the Frome to the Raglan.

After the dingle we had been kindly granted permission to climb the church tower of St Mary’s from where stunning views of the lumps and bumps of the Teme Valley can be observed.  Thank you to St Mary’s for this memorable visit, we were able to contribute £24 to church funds.

Following are my field notes for the evening:

Stanford Area Geology

The valley of the River Teme, mainly in this area, soft Raglan Mudstone of Silurian Age, rising up steeply to a layer of calcrete known as Bishops Frome, formed in a dry climate, where the lime in underlying formations leached out and to the surface to develop over millions of years a chemical layer of limestone.  Above that, sandstones and marl of the Devonian period, known as St Maughans, with itself quite a percentage of lime bearing compounds. Age is 416–397Ma and the formation is made up of red/purple/grey mudstones, sandstones, intraformational conglomerates and calcretes, deposited from a braided stream system which ran over a vast, flat, arid landscape. The unit is typified by cyclic sequences moving from an erosive base with basal conglomerate, up into finer siltstones and eventually calcrete (Bishops Frome here) with carbonate nodules. Sandstone lenses infilling river channels and other fluvial features of seasonal streams crossing a semi-arid land surface can frequently be seen. These rocks have often been quarried, both for aggregates and for building stones. The harder bands, such as the intraformational and calcretes have been used for road stone.

It is interesting to see the waterfall in Fall Coppice which I assume is caused by the water tumbling over the harder layer of what I term, Raglan Sandstone into the softer Raglan Mudstone below. According to the geology map (see above), this rib of sandstone extends across the road to near the church of St Mary’s and maybe this is the rock from which the church was built.

Fascinating too to see higher up, a lime kiln right on the limey Bishops Frome and used to burn lime for mortar and for the fields. There is an overgrown quarry just above the kiln and above the Bishops Frome so we deduce this is the St Maughans, here a usable sandstone, to be found in many buildings in the area. The valley below the kiln is notable for its precipitous sides, no doubt because the water having run across hard sandstones and the lime layer found it could cut its way into the softer mudstones below, only forming falls where it came across the harder formations.

Refer to my blog of 21st Feb 2015 as it has quite a bit on this whole area