IX.— Fossil Soils of the Upper Old Red Sandstone of South Ayrshire

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Abstract
Cornstones, concretionary limestones in the Scottish Upper Old Red Sandstone, are the limestone horizons in fossil calcareous soils (pedocals). The soil profile comprises three horizons; the topmost of red-brown sand, the middle of black marl with small impure calcareous nodules, and the lowest of relatively pure limestone (the cornstone proper), often showing colour banding and oolitic structure. The cornstone may be up to 15 ft. thick, and was formed in situ by replacement of the detrital quartz and felspar grains of the parent sand by microcrystalline calcite. The Ayrshire cornstones seem to resemble closely the Pliocene caliche limestones of South-Central U.S.A..