Soil formation follows a pattern that can be generalised by recognising a small number of master horizons as follows.
Standard letter symbols are used to denote the master horizons as follows:
0 - Organic horizon, consisting of organic materials formed at the surface under hydromorphic conditions
A - Horizon, formed at the surface or beneath a 0 horizon
E - Horizon, underlying the 0 or A horizon, reflecting a pale colour
B - Horizon, between the A or E or C or R horizons
C - Horizon, that could include weathered rock (saprolite) and lies beneath the lowest B horizon
R - Consolidated bedrock
G - Horizon, under an A or E horizon, showing strong signs of reduction under anaerobic
conditions