Wells

New Cut 2017-11-20

Leaders: Doug & Chris
Organiser: Jean

This walk started on Triassic rocks of the Mercia Mudstone formation representing the finer grained material shed from the Mendip Mts.

The section from the upper part of Reservoir Lane into the New Cut section marked the gradual change from the subaerial Triassic environment into an initial saline lagoonal setting represented by the Blue Anchor Formation. Then the following Westbury Formation and Blue Lias rocks represent the gradual encroachment of the sea with deeper water fossiliferous deposits of the Blue Lias (Jurassic rocks). The uppermost Jurassic unit present in the New Cut lane is the Charmouth Mudstone, but this is not exposed because it is easily weathered.

Towards the top of New Cut, Devonian sandstones were found in the track. These rocks are the oldest found in the immediate Wells area, and form the core of the Pen Hill anticline.

The return journey commenced in the Black Rock limestone of Carboniferous age, and where the path comes close to Tynings Lane this limestone unit is folded into a small scale structure as a result of the Variscan deformation. From this outcrop, it was then south past Model Farm to the starting point.

We were lucky enough to have with us an expert in geology teaching, who supplemented Doug's local knowledge with exercises like 'what was it like to be there?' and 'if I was all-powerful, how could I create this formation?'. These really made us think about the geology and the changing climatic conditions as the Mendip rocks were moved steadily North towards the equator and uplifted, eroded and then encroached upon by warm seas.

Description by Doug and John, pictures by Gaye and Stephen

Further information