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Soil Formation on Loess in Southwestern Indiana: II. Distribution of Clay and Free Oxides and Fragipan Formation
Author(s) -
Harlan P. W.,
Franzmeier D. P.,
Roth C. B.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100010029x
Subject(s) - loess , drainage , clay minerals , mineralogy , soil water , geology , expansive clay , soil horizon , silicate , soil science , chemistry , geomorphology , ecology , organic chemistry , biology
Fourteen soil profiles from southwestern Indiana were studied to determine the effects of loess thickness and natural soil drainage on the profile distribution of clay and free oxides (CBD‐extractable) of Fe, Al, Mn, and Si. In all soils, Fe and Al curves follow the clay curve, suggesting that the oxides are adsorbed on clays and move with them. Natural soil drainage had little effect on profile distribution of clay, Si or Fe. Free Al 2 O 3 contents increase slightly with poorer drainage. With thinning loess, clay and free Fe 2 O 3 distribution changes little, free Al 2 O 3 contents increase slightly, free MnO 2 curves have more pronounced minima and maxima, and free SiO 2 increases significantly in fragipan horizons. We propose that free silica moves down the profile in solution and precipitates, possibly with aluminum hydrous oxides on clays. The resulting silica or alumino silicate binds particles together to form the hard, brittle soil material of fragipans.