Abstract

Aluminous lateritic soils from Governor's Harbour, Eleuthera, Bahamas are described. These soils are forming on eolian ridges under a humid, tropical savanna climate. The parent material is carbonate eolianite plus airborne dust from North Africa. The soils are thin, discontinuous and concentrated in shallow solution pits. They are stony, have a crumb texture and are underlain by pedogenically altered limestones. The solum has a low SiO 2 /Al 2 O 3 ratio and is composed of boehmite, hydroxy-interlayered clay (HIC), Al-hematite, Al-goethite, calcite and minor quartz. The presence of carbonates in the solum buffers the pH and inhibits gibbsite precipitation, resulting in a high availability of aluminum for incorporation in HIC and iron minerals. The moisture regime of these soils is characterized by frequent wetting and drying due to the high porosity and permeability of the underlying carbonates, and the intermittent nature of the rainfall. Boehmite is the stable Al-phase within cryptovoids where the H 2 O activities are less than one. The dominant pedogenic features in the altered limestones are voids produced by solution of limestone around plant roots. These voids are subsequently infilled with overlying solum material and cemented with equigranular calcite. Alteration rinds containing micritized carbonate grains, and laminations of micrite and iron-rich clay develop around the voids. Features observed in aluminous lateritic soils are compared to other carbonate soils and paleosols preserved within carbonate sequences.

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