Council’s Bathscape project shares geological and other analysis

B&NES’ Bathscape project has started to produced summaries and analysis of the landscape around the World Heritage City. See below for example for what they have to say about the geology of Kelston Roundhill:

The geology of this area is topped primarily by Fullers Earth Rock From the Greater Oolite Group of the Middle Jurassic Period. Kelston Roundhill stands proud of the Fullers Earth Rock and comprises a cap of Greater Oolite Limestone below which is Upper Fullers Earth and then the Fullers Earth Rock. Below the Fullers Earth Rock is a layer of Lower Fullers Earth and then below that a harder layer of Inferior Oolite Series limestone followed by Midford Sand from the Upper Lias Group and finally Lower Lias Clay. In terms of surface geology, the Lower Lias Clay and Midford Sand form the substantial part of the lower and middle slope of the escarpment, the Inferior Oolite forms the upper middle slope and the Fuller Earth the upper slopes with Greater Oolite limestone capping Kelston Roundhill.

The alternating layers of harder Oolite limestones and softer clays and sands has given rise to which are of key importance in shaping

the landform of the Escarpment and Enclosed Limestone Valley landscape types of the Bathscape area. Landslips have occurred through a long period of geological time right up to the present. In this character area landslips have affected the area as follows: below Prospect Stile; the Midford Sand belt just at the head of the tributary valley between Prospect Stile and Kelston Roundhill; all around the limestone cap of Kelston Roundhill in the Upper Fullers Earth band and then continuing downhill to the west and south of Kelston Roundhill in the Fullers Earth Rock and Lower Fullers Earth; over the whole of the south end of the escarpment between the Cotswolds Way and Kelston village.

These landslides and a process known as cambering where blocks of capping limestone break off and slip down-slope, are responsible for the highly undulating valley sides and escarpment within the Bathscape area. Undulations and bulges form both along the slope and down the slope where the softer clays and sands are squeezed out between and below the harder limestones; with steeper angles where the harder limestones are present usually at the top of the slope and then around halfway down where the Inferior Oolite limestone often forms bench-like outcrops.

In the Prospect stile to Dean Hill character area all these effects are present. In addition tributary streams of the River Avon form more marked indentations in the escarpment slope, in particular running down to the west from below Prospect stile.

Overall the escarpment is moderate to steeply sloping throughout with limited areas of shallower slopes in an uneven distribution over the slope. The highest points are at Prospect stile (238m) and Kelston Roundhill (218m) with the general top of the escarpment at around 170m decreasing towards Dean Hill down to 120m.

Kelston Roundhill forms a major landmark on the skyline where it forms a distinctive conical hill topped by a clump of trees. Its distinctive outline is visible for miles around including from many parts of Bristol city.

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