SOIL GENESIS ON FELSIC ROCKS IN THE ST. FRANCOIS MOUNTAINS. II. THE DISTRIBUTION OF ELEMENTS AND THEIR USE IN UNDERSTANDING WEATHERING AND ELEMENTAL LOSS DURING GENESIS

Abstract

Two soil profiles from felsic materials from Mudlick Mountain in the St. Francois Mountains of Southeast Missouri were investigated to determine if these soils evolved from the underlying rock unit, to determine the partitioning of metals into the Fe-oxide fraction, and to evaluate this metal partitioning as influenced by clay illuviation. Chemical extractions, neutron activation analysis (NAA), and classical total element determinations show that: (i) Zr and K are not preferentially accumulated by clay, (ii) V and Sc are preferentially accumulated by Feoxides, (iii) Ca and Na are almost completely removed from the soil environment; Mg, K, Fe, Mn are partially removed from the soil environment; and Si and Al are largely incorporated into secondary minerals, reducing their loss rates from the soil environment. The rare earth elements (REEs) are not strongly removed from the soil system. Measurements of cation solubility suggest that Al, K, and Na are appropriate for soil systems having a kaolinitic mineralogy. Landscape position influenced elemental loss rates, with a soil on a relatively level landscape position having lower elemental loss rates that an adjacent soil on a steeply sloping position. The influence of lateral water flow in subsurface horizons may be involved in weathering rates and the loss of elements.