Berndt-Michael Wilke

Clay mineralogy of a soil sequence in slope deposits derived from hauptdolomit (dolomite) in the bavarian alps

Abstract Clay mineralogy was determined in a sequence of soils formed in slope deposits derived from Hauptdolomit and ranging from a Mullrendzina (Rendoll) to a Terra fusca (Eutrochrept) and a Parabraunerde-Terra fusca (Hapludalf). Results indicated an alteration of illite to hydroxyl-Al interlayered clay in the course of soil formation. No evidence was found of formation of kaolinite in these soils. This clearly confirms all soils to have been formed under a recent cold humid climate. Furthermore clay mineral weathering starts even before carbonates are dissolved and completely removed from these soils.

Mineralogies of silt and clay fractions of twelve soil profiles in the Bolivian Andes (Callavaya Region)

Abstract Mineralogies of a soil catena in the Pampa of Ulla Ulla (4,300–4,600 m) and the soils of the steep slopes of the Cordillera de las Munecas (“steep area”) were investigated. The latter area includes three altitudinal zones: herbaceous zone (3,900–4,800 m), shrub zone (2,700–3,900 m), and mountain forest zone (up to 2,700/2,800 m). The soils were classified according to Soil Taxonomy as Entisols, Mollisols, and Inceptisols. They were mainly derived from quartzitic schists and slope debris. Each horizon of each profile was representatively sampled for analyses. Muscovites and illites were the dominant minerals in the fine silt and clay fraction, respectively. Besides kaolinite, pyrophyllite and vermiculite, regular illite/vermiculite mixed layers, chlorite, feldspar and quartz were detected in both fractions. In a Typic Cryaquent from the Pampa of Ulla Ulla, smectites had been formed. Pyrophyllite, illite/vermiculite mixed layers and chlorite seemed to be unstable under acid conditions in most of these soils.