Duripan Horizon and Durinodes - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 140

14.4 Distribution of Soils with Duripans and Durinodes
In the USA Duric soils cover 106,600 km 2 and occur in eight states (Fig. 14.3 ).
They are most abundant in the arid parts of the Western states and in particular in
NV, followed by ID, OR, CA, WA, AZ, and UT. The soil mapping units shown in
Fig. 14.3 contain duric soils at the suborder and primary great group levels for
conterminous USA. Great groups with less than 10 soil series and soil series that are
duric or durinodic at the subgroup level are not included. Duric soils have not been
reported or mapped in WY, CO, or TX, despite that conditions would appear to be
ideal for durinode and duripan formation.
14.5 Soil-Forming Factors Influencing the Formation
of Duripans and Durinodes
Soils with duripans and durinodes predominantly occur in the western parts of the
USA. Flach et al. ( 1969 ) suggested that silica cementation in the western USA
occurs under two combinations of soil-forming factors: (i) old alluvial fans on the
western slope of the Sierra Nevada in a subhumid, Mediterranean climate and
Fig. 14.3 Distribution of Durids suborder and major Dur- great groups in conterminous USA
(Prepared by Dr. Paul Reich)