GENESIS OF DIOCTAHEDRAL CHLORITE-LIKE CLAYS IN TERRA ROSSA SOILS IN SOUTH FLORIDA

During an investigation of terra rossa in south Florida, a chlorite-like mineral was found to be the sole clay mineral present in the soils. The clay has accumulated and/or formed in the porous, well-drained oolitic facies portions of the Miami Limestone, especially on the Atlantic Coastal Ridge. This clay mineral is an aluminous, dioctathedral variety that shows x-ray diffraction characteristics indicative of a pedogenic origin. Previous theories that have been proposed for formation of pedogenic chlorite-like clays are not applicable to this occurrence. Therefore an alternative model, based on carbonate inhibition of gibbsite precipition, is proposed for hydroxyinterlayering of clays in carbonate-rich soils and for the formation of chlorite-like clay minerals in terra rossa.