The Fuller's Earth of the Cotswolds, and its relation to the Great Oolite

Abstract

Summary Lateral changes in the Fuller' Earth formation along the 50 miles of strike from the Avon valley at Bath to the Vale of Moreton at Stow-on-the-Wold are investigated by means of six-inch mapping of five selected areas. It is shown that the Fuller' Earth Rock of the Bath district when traced northwards into the southern part of the South Cotswolds becomes two distinct rock bands separated by up to 30 feet of clay, so that there are two Fuller' Earth Rocks and three Fuller' Earth Clays. In passing farther northwards, first the upper clay wedges out near Horton, then the upper rock passes laterally into Great Oolite “ White Limestone ” near Tresham, and false-bedded oolites come in below it; next the middle clay (which is the Upper Fuller' Earth of the northern part of the South Cotswolds and of the mid-Cotswolds) wedges out on approaching Nails worth; next the lower rock passes laterally into Great Oolite “ White Limestone ” near Nympsfield, and at the same time the false-bedded oolites of Minchinhampton come in below it; and finally the Lower Fuller' Earth Clay wedges out towards Stow-on-the-Wold and Burford and is at least partly replaced by the Chipping Norton Limestone. The paper shows in detail that S. S. Buckman's correlation fifty years ago of the Fuller' Earth Rock of Somerset with part of the Great Oolite of Gloucestershire, made on the strength of the ammonites, was correct. The lateral changes and alternations of facies are summarised in horizontal sections (Pl. XVI).