Note on the Petrology of the Drybrook Sandstone of the Forest of Dean

Extract

THE late Dr. Vaughan, in 1905, established the age of the sand-stone lying above the Whitehead Limestone of the Forest of Dean as of upper Seminula age, and not, as had been supposed, as the equivalent of the Millstone Grit. Later, in 1912, Dr. T. F. Sibly described the sandstone as “ composed very largely of pure quartz sandstones, often coarse-grained and friable. Conspicuous bands of quartz conglomerate occur: some clays and shales are intercalated, with the sandstones: and some haematite deposits are developed ”. The same author described the structure of the Forest of Dean coalfield and noted the perfectconformity of the Dry brook Sandstone on the Whitehead Limestone and the overstep of theCoal-measures. The latest description of the sandstone, and the one which is most complete, is given by Dr. Sibly in his work on the ironstone of the Forest of Dean. His description reads “ Red, white, and mottled red and white sandstones compose the bulk of the formation. The rocks are mainly friable, but compact and even quartzitic rocks occur. In the north-east seams of quartz conglomerate are numerous. In the south-west bands of gritty limestone and dolomite develop ”.