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Diagnostic Subsurface Horizons
diagnostic subsurface horizons
17
Environmental Studies
Undergraduate 4
09/23/2015

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Term
Agric
Definition
-illuvial horizon formed under cultivation
-significant amounts of illuvial silt, clay and humus
-directly below Ap horizon
-thickness of 10cm or greater
Term
Albic
Definition
-eluvial horizon that is lightly colored and low in clay and oxides (leaching)
-1cm or greater
-separate horizons that, if they were together, would meet requirements for a mollie epipedon or separate lamellae that together would be an argillic horizon
Term
Anhydritic
Definition
-anhydrite accumulation through neoformation and transformation
-hue of 5Y, chroma (moist and dry) of 1 or 2, and value of 7 or 8
Term
Argillic (Bt)
Definition
-significantly higher percentage of phyllosilicate clay than overlying soil material
-clay illuviation
-total clay in illuvial horizon is greater by 1.2 times or more than the ratio in the alluvial horizon
Term
Calcic (Bk)
Definition
-illuvial accumulation of calcium carbonates
-15% more CaCO3 equivalent, and 5% identifiable secondary carbonates
-"Petrocalcic" if secondary CaCO3 accumulated and cemented
Term
Cambic (Bw)
Definition
-has not undergone enough illuviation to become argillic
-sandy loam or finer (not loamy sand)
-different color and structure from C horizon due to chemical transformations, or removals or a combination
-colors that do not change on exposure to air
-absence of rock structure
Term
Duripan (Bq)
Definition
-silica-cemented subsurface horizon
-can occur in conjunction with petrocalcic horizon
-accumulation of silica (coatings, lenses, bridges, etc)
-pan is cemented or indurated in more than 50% of the volume of some horizon
Term
Fragripan (Bx)
Definition
-evidence of pedogenesis
-coarse prismatic, columnar or blocky structure
-not effervescent
-layer is 60% or more of the volume, a firm or firmer rupture-resistence class, a brittle manner of failure at or near field capacity and virtually no roots
Term
Glossic
Definition
-degredation of an argillic, kandic or natric horizon from which clay and free iron oxides are removed
-eluvial part that constitutes 15-85% (by vol) of glossic horizon
Term
Gypsic (By)
Definition
-accumulated or transformed gypsum
-not cemented by gypsum (with or without cementing agent)
-5% or more of gypsum
-"Petrogypsic" if secondary gypsum has accumulated or been transformed and cemented (40% or more gypsum)
Term
Kandic
Definition
-accumulation of Fe and Al oxides and kaolinite clays
-low cation holding capacity
-product of intense weathering
-loamy VF sand or finer
Term
Natric (Btn)
Definition
-like argillic with the addition of sodium
->15% exchangeable sodium
-columnar structure
-evidence of clay illuviation
Term
Oxic (Bo)
Definition
-highly weathered subsurface very high in Al and Fe
-humid and subtropical environments
-10% weatherable minerals in sand, silt or clay, all other minerals have weathered to elements
-does not have antic soil properties
-30 cm or greater
-sandy loam or finer
Term
Placic
Definition
cemented by iron (or iron and manganese) and organic matter
Term
Salic (Bz)
Definition
accumulation of salts more soluble than gypsum
Term
Sombric
Definition
-dark subsurface horizon that formed under free drainage
-illuvial humus that is neither associated with Al nor dispersed by Na
-does not have high CEC in its clay
-lower color value and/or chroma than overlying horizon
Term
Spodic (Bhs or Bs)
Definition
-illuvial layer with 85% or more spodic materials (greater than 2.5 cm)
-spodic materials are colloidal organic matter, aluminum oxide and iron
-underlies O, A or E horizon
-common in leached forests of cool humid climates
-on sandy PM
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