Pedogenesis of black shale-influenced soils of the Knobs region of eastern Kentucky

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5884300

Sobecki, T M

Investigation of acid soils on forested hillslopes truncating Devonian-age black shales in the Knobs of eastern Kentucky established the impact of parent material and landscape position on colluvium occurrence and soil properties. Colluvium was thickest in headslopes, thinner in nose- and sideslopes, where illitic Typic Hapludults formed in acid gray and black shale residuum and colluvium, and sandstone colluvium. Base saturation and pH increased with depth in nose- and sideslopes, and decreased with depth in headslopes. The pH of black shale colluvium and residuum was {lt}4.0 in noseslopes, and Al saturation {gt}90%. Morphology, particle size, and TiO{sub 2}/ZrO{sub 2} ratios were used to assess parent material homogeneity and colluvium source. Compositions of soil solutions, mineral stability, and clay mineral analyses were used to evaluate illite weathering. Smectite randomly interstratified with illite was an initial illite weathering product in the noseslope black shale soil. High charge smectite (HCS), randomly interstratified with illite, predominated in noseslope pedons of black and gray shale, however. Vermiculite occurred in black and gray shale headslope pedons. Lithologic discontinuities prevented attribution of clay mineral suites solely to weathering. Soil solution compositions, clay mineral ratios, and thermodynamic stability of the clay minerals, however, suggested a weathering sequence of illite {yields} smectite {yields} HCS or vermiculite {yields} kaolinite or complete dissolution. Column leaching experiments suggested carbon, iron, and sulfur loss as the initial black shale weathering step, with silicate alteration following at a later stage. Young landscapes coupled with the loss of soluble weathering products from these soils is suggested as an explanation for the maintenance of illitic mineralogy despite undersaturation with respect to illite.

• Research Organization: Kentucky Univ., Lexington, KY (USA)
• OSTI ID: 5884300
• Country of Publication: United States
• Language: English

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040200* -- Oil Shales & Tar Sands-- Reserves
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ALUMINIUM SILICATES
ALUMINIUM SULFATES
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BITUMINOUS MATERIALS
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FORESTS
FOSSIL FUELS
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GEOLOGIC AGES
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OXYGEN COMPOUNDS
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PARTICLE SIZE
PH VALUE
POTASSIUM COMPOUNDS
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ROCKS
SANDSTONES
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SEPARATION PROCESSES
SILICATE MINERALS
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SILICON COMPOUNDS
SIZE
SMECTITE
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TITANIUM COMPOUNDS
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VERMICULITE
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