Morphology of Calcite Crystals in Clast Coatings From Four Soils in the Mojave Desert Region

Abstract

AbstractPedogenic calcite‐crystal coatings on clasts were examined in four soils along an altitudinal gradient on Kyle Canyon alluvium in southern Nevada. Clast coatings were studied rather than matrix carbonate to avoid the effects of soil matrix on crystallization. Six crystal sizes and shapes were recognized and distinguished. Equant micrite was the dominant crystal form with similar abundance at all elevations. The distributions of five categories of spar and microspar appear to be influenced by altitudinally induced changes in effective moisture. In the drier, lower elevation soils, crystals were equant or parallel prismatic with irregular, interlocking boundaries while in the more moist, higher elevation soils they were randomly oriented, euhedral, prismatic and fibrous. There was little support for the supposition that Mg2+ substitution or increased (Mg + Ca)/HCO3 ratios in the precipitating solution produced crystal elongation.