The Firestone Sill ganister, Namurian, northern England—the A 2 horizon of a podzol or podzolic palaeosol

Abstract

The Firestone Sill is a sandstone of early Namurian age which outcrops in the northern Pennines. Occasionally the top of this sandstone contains a conspicuous white quartz arenite upto 1.5 m thick. This was formerly worked for refractory purposes and became known as the Firestone Sill ganister. The presence of roots, rootlets, soil horizons and pedogenically produced structures, e.g. cutans associated with the quartz arenite suggest that it represents the A 2 (eluvial) horizon of a podzol or podzolic palaeosol. The main processes operating during pedogenesis were the accumulation and incorporation of organic matter into the surface (A 1) horizon, destruction of sedimentary structures by bioturbation (principally rootlets), and the downward translocation of carbonaceous material, clays and other mineral breakdown products. The latter led to a relative quartz enrichment of a few percent in the A 2 (ganister) horizon and resulted in the development of a B-horizon of accumulation. The presence of occasional feldspars in the A 2-horizon and the rather small amount of quartz enrichment which took place in this zone suggest that pedogenesis was of fairly brief duration.