The Carboniferous Limestone of the Mitcheldean Area, Gloucestershire

Abstract

At the north-east comer of the Forest of Dean coalfield, immediately west of the village of Mitcheldean, the strata are sharply folded into a pitching syncline—the Wigpool syncline —which tapers out northwards and merges southwards into the main basin of the coalfield. Here the Carboniferous rocks form a triangular plateau which rises sharply from the Old Red Sandstone country. The Carboniferous Limestone of this small area, measuring some two miles from north to south and a little over one mile in maximum width from east to west, is the subject of the present paper. The strata are remarkably well exposed in numerous quarries, and the succession can be studied in almost complete detail. The following lithological classification of the Lower Carboniferous rocks in the Forest of Dean was proposed in 1919:— 1 This series of strata rests conformably upon the Old Red Sandstone, but it is overlain unconformably by the Coal Measures. Wethered had dealt with the strata and fossils of the Carboniferous Limestone near Mitcheldean in three papers published during the period 1883–88, while Vaughan published in 1905 a brief account of the sequence and a zonal correlation, and demonstrated the Lower Carboniferous age of the local “Millstone Grit”. In 1912, one of us gave some further account of the succession, described the unconformable relationship of the Lower Carboniferous strata and the Coal Measures, and proposed the name Dry brook Sandstone for the “Millstone Grit”. In 1918, the S 2 age of the Drybrook Sandstone was definitely established by the discovery of