Melanic Epipedon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 21

Fig. 4.1 A soil containing a melanic epipedon from the southern Oregon coast (Photo by
J. Bockheim)
4.3 Classification of Soils with a Melanic Epipedon
The melanic epipedon has been identified taxonomically, i.e., in Melan- great
groups, in only 11 soil series (Table 4.2 ). However, an additional 18 soil series
appear to have the required properties of a melanic epipedon, but either the OSDs
have not been updated or confirming laboratory data have not been obtained.
Of these 19 soil series, 15 are in Pachic subgroups. All but one of the series have
a medial or medial-skeletal particle-size class, 16 of 29 have a ferrihydritic
mineralogy, and 15 of 29 have either a cryic, frigid, or isofrigid soil-temperature
regime.
4.4 Distribution of Soils with a Melanic Epipedon
Soils with a melanic epipedon occur nearly exclusively in western Washington
(WA), western Oregon (OR), with smaller areas in north-central WA, northwestern
Montana (MT), and north-central California (CA; Fig. 4.2 ). These soils cover an
area of about 595 km 2 .