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

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-bfown 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..

The Upper Old Red Sandstone of Fife and Kinross: a fluviatile sequence with evidence of marine incursion

“…The proportion of feldspar is higher (p. 4) than in the Knox Pulpit or Glenvale formations, suggesting some renewed uplift in the source of sediment supply; the reappearance of siliceous pebbles points to the same conclusion. The concretionary carbonate nodules resemble the 'cornstones' described from rocks of similar age and facies elsewhere (Burgess 1961;Read, in Francis et al 1970, pp. 103-107), and a similar interpretation is placed on them, namely that they developed as caliche-like deposits in soil profiles, under the influence of a semiarid climate (Reeves 1970, p. 353).…”

“…At the western end of the region, in the Clyde coastal area (Bluck 1967) and in south Ayrshire (Burgess 1961), sediment was transported in a mainly northward direction, and the presence of conglomerates indicates a relative proximity to source areas. In the central part of the region, in Stirlingshire, there are fewer pebbly deposits and sediment transport was mainly to the south-east (Read and Johnson 1967).…”

Sedimentology and palaeogeography of the Upper Old Red Sandstone in the Scottish Border Basin

“…Upper O.R.S. fluviatile sediments outcrop around the margins of this basin and show off-block palaeocurrent trends from the Southern Uplands, Scottish Highlands and intra-graben upland areas (Burgess i960;Read and Johnson 1967;Bluck 1967). The latter author describes sediments of alluvial fan (including mudflows), braided stream and floodplain origin from the Clyde area.…”

Desert Crusts and Rock Coatings

“…Hubert (1978), for example, held that palaeosol calcretes in Connecticut show signs of 50-95 % replacement; McFarlane (1975) suggested that a fabric of floating garnet grains in some Kenyan calcretes represented the residuum of a replaced host material. Many calcretes exhibit signs of replacement of clay (Hay and Reeder, 1978), feldspars and quartz (Burgess, 1961;Chapman, 1974), but the latter may be diagenetic rather than syngenetic features. Displacive, replacive and passive void-filling can all take place (Yaalon and Singer, 1974;Watts, 1980;, but their relative importance varies according to host lithology and environmental conditions.…”