Inferior Oolite - is a yellow-weathering, limestone of the Middle Jurassic. The limestone is richly fossiliferous with brachiopods, bivalves, ammonites and echinoids. The sequence contains oolitic horizons representative of shallow high-energy marine environments. There is often evidence of breaks in sedimentation, as shown by eroded, bored or oyster-covered surfaces, as well as conglomeratic horizons. The best known rock in this area is from the Doulting quarries which has been quarried as a building material, especially for Glastonbury Abbey and Wells Cathedral.

Lias Group - the Charmouth Mudstone formation is the youngest of the Lias Group, but much of the succession is missing, and what is present is poorly exposed. Between Shepton Mallet and Wells, the usual interbedded succession of mudstone and thin limestone of the Lias is replaced entirely by conglomeratic limestone known as Downside Stone and Chilcote Stone. This is an ancient shoreline deposit formed around the Mendip archipelago. There are beds of broken, thick­shelled bivalves, with Carboniferous limestone clasts indicating continued erosion of the Mendips. The Downside stone is exposed at Bowlish where it forms interbedded grey limestones and mudstones indicating a change in deposition from a nearshore to a deeper (but remaining relatively shallow) offshore. Ammonites, gastropods, bivalves and coral, have been reported along some wood fragments indicating the proximity of land.

The Lias Group more typically forms regularly interbedded thin limestones and dark mudstones, and are richly fossiliferous, with ammonites and bivalves. They were deposited in open-water, some distance from landmasses, and so are not represented near Shepton.

Silurian and Devonian - North of Croscombe and Shepton is the E­W trending Beacon Hill, the easternmost of four periclines forming the core of the Mendip Hills.

The oldest rocks in the Mendips are exposed in the core of this pericline - the Silurian, Coalbrookdale Formation. It is a sequence of mudstones overlain by tuffs, agglomerates and andesitic lava flows – one of the few places in the UK where Silurian volcanics are exposed.

The immediate envelope to the Silurian core is formed of Devonian rocks of the Portishead Formation, representative of a fluviatile system in an arid, continental environment at the southern margin the Caledonian mountains. The rocks are dominantly red sandstone, with some purplish shales and mudstones.

After this taste of recent history we drove to the Doulting Stone Quarries which record more ancient events.

The Doulting Quarries were used by the Romans as shown the use of Doulting stone cut quoins in the remains of a building in Shepton Mallet, next to Fosse Lane. The quarry became important in Medieval times with the building of Glastonbury Abbey, and it was in possession of the Abbey from the 8th or 9th century. This makes it one of the oldest and longest worked quarries in the UK. The Abbey's tight control limited use of the stone to largely ecclesiastical buildings, with even the Dean and Chapter of Wells Cathedral having difficulty in obtaining supplies. This constraint meant that the local Chilcote stone (over which the Dean did have control), was initially more widely used around Wells. Each subsequent stone extraction episode was subject to a new arrangement, such as in 1354 when Walter de Monyngton (Abbot of Glastonbury) granted William de Camel, Canon of Wells, 40 wainloads of freestone for the new cloister house and 20 loads for other works. The cost of haulage to Wells in the 1400s was 12d (5p) per load. Records in 1381 specifically refer to Chelynch Quarry (which operated for six centuries, closing in 1967). The quarry was in fact a patchwork of operations from Chelynch in the north to the present site in Doulting.