Published online by Cambridge University Press: 01 May 2009
The BP Exploration Company's Colston Bassett (South) No. 1 Borehole, Nottinghamshire, entered Coal Measures at 1,134 feet. These persisted for 901 feet, when massive tuffs were encountered which were 679 feet thick and overlay Millstone Grit. The tuff is composed of amygdaloidal glass, devitrified to a montmorillonite, and is rich in analcime. In a nearby borehole, no tuffs were encountered and the Coal Measures were 1,784 feet thick. It seems that at Colston Bassett (South) the lowest Coal Measures sediments are represented by the tuff, which is non-displacive and was perhaps a cone against which the later sediments were deposited.