A talk by Garry Dawson

A packed house heard Garry’s fascinating talk about the geological history and building stones of the Quantock Hills. When Garry retired, he offered his services as a volunteer at SW Heritage Trust. He was invited to carry out a survey of the building stones in the area. He and Peter Wright, who has since passed away, undertook the survey, the rationale of which was to inform the repair/restoration of historic buildings to maintain local character, education and research (many quarries have been filled in) and history – the consequences of changes over time.

Their method was to research what had already been done both county-wide and in local areas. They walked through settlements (281 villages) noting local stone types in buildings (mainly pre-WW1) and churches. Post WW1 buildings tend to use building materials imported from other areas. Individual houses were not included. The Heritage Trust also asked them to survey non-stone materials. A simple data collection form was circulated.

Garry outlined the general geology of the Quantocks. Somerset has a wide range of rocks laid down over the ages:

1. North Quantocks – Hangmans Sandstone, tending to be found in the highest parts of the Quantocks; this oldest rock is very hard and erosion resistant– and Lynton Slates. Hangmans Sandstone dates from the early to middle Devonian era and is mainly sandstone deposited by large river systems. Some plant fossils have been found, including the world’s oldest fossilised forest found at Minehead in April 2024. Cross-bedding can be seen – like sideways ripples as in a river. These very hard rocks are used for roads, aggregates and buildings and were quarried in places like Triscombe and Bicknoller.
2. Central & Eastern Quantocks – Ilfracombe slate – found at Cothelston and towards the East. These rocks extend across Somerset and into North Devon (hence the name). These rocks date from the Middle Devonian and are younger rocks than Hangmans. Mud deposits can be found, often calcareous, which form in shallow oceans. They are not true slate and so are no good for roofs. Woodland and some pastures are found on these rocks. Fossiliferous limestone is found. Lime kilns were built in these areas, e.g. Hawkridge Common, where an interpretation board can be seen. Two limestone quarries can be found at Little Great Wood, Aisholt and Holwell, where a large coral fossil was found.

Keepers Combe is an example of Cockercombe Tuff which are greenish volcanic deposits. Sadly, there is no evidence of a source volcanic site.

• South Quantocks – Morte Slate, named after the North Devon location. Found at Cothelstone down to Kingston. It was created in a shallow ocean with no limestone. This is not true slate. In places, some thick sandstone can be found, which can be used for building. There is evidence of quite a lot of glacial hill creep where there was fault movement, as found at Thurloxton. Morte Slate was quarried at Fyne Court and Kings Clyffe, North Petherton. At Hestercombe the Morte Slate rock was altered by the intrusion of heat so that it became extremely hard. This hardened rock was used as whetstones in the 18^th century.

Beyond the Quantocks can be found Otter sandstones and Budleigh Salterton pebble beds. Red sandstones were used for building eg Bishops Lydeard Church.

The International Union of Geological Sciences named the structure of the Somerset Coast amongst its top 200 geological sites. The Coastal SSSI consists of Blue Lias mudstones and limestones. The Old Shale Retort at Kilve was an unsuccessful attempt to extract oil from the shale.

Alternating limestone/mudstone deposits due to possibly changes in the earth’s orbit have revealed a rare “Golden Spike” at East Quantoxhead – revealing a moment of change in the evolution of ammonites. There are only about 10 Golden Spikes in the UK and Somerset’s coast has one.

Copper was mined at Dodington in the Buckingham Mine, and small amounts of lead and silver are found in the Quantocks.

Survey Results

Quantock area stones for building are the Triassic and Hangmans Sandstone which were used in walls of churches and older buildings.

Softer stone, easier to work and carve, was imported, e.g. Bath Stone for door and window surrounds. Churches were more likely to import stone as they had the financial resources to do so. People through the ages have used building stones found close at hand until the age of canals and railways with easier transport.

As you travel past buildings, you can see examples of the use of local rocks:

• Quantock Lodge includes Cockercombe Tuff with its greenish tinge.
• Fyne Court boat house consists of morte slate and sandstone.
• Bicknoller Church local red sandstone.

Some buildings, e.g. churches, have layers of different rocks.

Further reading:

Garry Dawson and Peter Wright’s remarkable survey can be found on the SW Heritage Trust website https://swheritage.org.uk/historic-environment-service/built-heritage/traditional-building-stone-research/

GREEN, Dave (2022) The Quantocks and North Somerset Coast: landscape and geology. Crowood Press. Isbn 0719840430

Garry recommended the British Geological Viewer app, which can be used as you walk around to see the geology beneath your feet https://www.bgs.ac.uk/map-viewers/bgs-geology-viewer/