Si, humus, CaCO3, CaSO4; or loss of CaCO3; or accumulation of sesquioxides; or subsurface soil structure. C: Little or no pedogenic alteration, unconsolidated earthy material, soft bedrock. L: Limnic soil materials. W: A layer of liquid water (W) or permanently frozen water (Wf) within or beneath the soil (excludes water/ice above soil). M: Root-limiting subsoil layers of human-manufactured materials. R: Bedrock, strongly cemented to indurated. Transitional horizons and layers A horizon that combines the characteristics of two master horizons is indicated with both capital letters, the dominant one written first. Example: AB and BA. If discrete, intermingled bodies of two master horizons occur together, the horizon symbols are combined using a slash (/). Example: A/B and B/A. Horizon suffixes a: Highly decomposed organic matter (used only with O). aa: (proposed) Accumulation of anhydrite (CaSO4). b: Buried genetic horizon (not used with C horizons). c: Concretions or nodules. co: Coprogenous earth (used only with L). d: Densic layer (physically root restrictive). di: Diatomaceous earth (used only with L). e: Moderately decomposed organic matter (used only with O). f: Permanently frozen soil or ice (permafrost); continuous subsurface ice; not seasonal ice. ff: Permanently frozen soil (“dry” permafrost); no continuous ice; not seasonal ice. g: Strong gley. h: Illuvial organic matter accumulation. i: Slightly decomposed organic matter (used only with O). j: Jarosite accumulation. jj: Evidence of cryoturbation. k: Pedogenic CaCO3 accumulation (<50% by vol.). kk: Major pedogenic CaCO3 accumulation (≥50% by vol.). m: Continuous cementation (pedogenic). ma: Marl (used only with L). n: Pedogenic, exchangeable sodium accumulation. o: Residual sesquioxide accumulation (pedogenic). p: Plow layer or other artificial disturbance. q: Secondary (pedogenic) silica accumulation. r: Weathered or soft bedrock. s: Illuvial sesquioxide and organic matter accumulation. se: Presence of sulfides (in mineral or organic horizons). ss: Slickensides. t: Illuvial accumulation of silicate clay. u: Presence of human-manufactured materials (artifacts). v: Plinthite. w: Weak color or structure within B (used only with B). x: Fragipan characteristics. y: Accumulation of gypsum. yy: Dominance of gypsum (≈≥50% by vol.). z: Pedogenic accumulation of salt more soluble than gypsum. Other horizon modifiers Numerical prefixes are used to denote lithologic discontinuities. By convention, 1 is not shown. Numerical suffixes are used to denote subdivisions within a master horizon. Example: A, E, Bt1, 2Bt2, 2BC, 3C1, 3C2. Horizons and layers according to the FAO Guidelines for Soil Description (2006) Source: Master horizons and layers H horizons or layers: