Pedogenesis and mineralogy of a Halaquept in Niger (West Africa)

• Published in: Geoderma 1988-10, Vol.43 (1), p.49-64
• Main Authors: Bui, Elisabeth N., Wilding, L.P.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; genesis del suelo; mineralogia; mineralogie; mineralogy; niger; pedogenese; Soil genesis; Soil science; Soil surveys, classification and mapping, soil genesis; Soils; Surficial geology
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(88)90054-7

In a fossil river valley of Niger known as the Dallol Bosso, an aquic soil environment has Fe-oxide segregation coupled with biological SO 4-reduction and Na 2CO 3 formation by evaporative pull. Depth to the water table, pH and water-soluble salts fluctuate seasonally but, most of the year, the water table is within 1 m of the surface. The presence of Na 2CO 3 is inferred from salt efflorescences and a pH of 9 at the soil surface in the dry season. The zone of Fe-oxide accumulation occurs between 30 and 54 cm and a soil layer with greyish green color and reduced Fe is present at the top of the water table. On the basis of field and laboratory characteristics, the soil is classified as an Aeric Halaquept. Mineralogical analyses (XRD, IR and SEM) show that goethite is the dominant iron oxide mineral and suggest that silica translocation in an iron-rich soil environment is promoting neoformation of iron-rich beidellite.