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JDA.Durixeralfs

Key to Great Groups 

JDA. Xeralfs that have a duripan that has its upper boundary within 100 cm of the mineral soil surface. Durixeralfs, p. 254 

JDA. Durixeralfs are the Xeralfs that have a duripan that has an upper boundary within 100 cm of the soil surface but below an argillic or natric horizon. These soils are known to have formed in California, Idaho, Nevada, Oregon, Chile, and Italy, in areas of Pleistocene or earlier vulcanism. Some of the Durixeralfs in the United States appear to be on very old surfaces and have complex horizons that indicate polygenesis. The oldest soils are commonly reddish and have kaolinitic mineralogy. Other Durixeralfs appear to have formed in late-Pleistocene sediments and are yellowish brown and have 2:1 lattice clays. The pan commonly has an upper boundary about 50 cm below the soil surface and has very coarse polyhedrons, the tops and sides of which are coated with opal or chalcedony. In undisturbed areas in the United States, a microrelief of about 10 to 100 cm or more is common. The microrelief is mainly the result of differences in the thickness of horizons that are above the duripan. Durixeralfs are moderately extensive only in California and Idaho in the United States

Definition 

Durixeralfs are the Xeralfs that have a duripan that has an upper boundary within 100 cm of the mineral soil surface. 

Key to Subgroups 

JDAA. Durixeralfs that have a natric horizon. Natric Durixeralfs 

JDAB. Other Durixeralfs that have, above the duripan, one or both of the following:

1. Cracks that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick; or

2. A linear extensibility of 6.0 cm or more. Vertic Durixeralfs 

JDAC. Other Durixeralfs that have, in one or more subhorizons within the argillic horizon, redox depletions with chroma of 2 or less and also aquic conditions for some time in normal years (or artificial drainage). Aquic Durixeralfs 

JDAD. Other Durixeralfs that have both:

1. An argillic horizon that has both:

                a. A clayey, clayey-skeletal, fine, or very-fine particlesize class throughout some subhorizon 7.5 cm or more thick; and

                b. At its upper boundary or within some part, a clay increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more (absolute) within a vertical distance of 2.5 cm, in the fine-earth fraction; and

2. A duripan that is strongly cemented or less cemented in all subhorizons. Abruptic Haplic Durixeralfs 

JDAE. Other Durixeralfs that have an argillic horizon that has both:

1. A clayey, clayey-skeletal, fine, or very-fine particle-size class throughout some subhorizon 7.5 cm or more thick; and

2. At its upper boundary or within some part, a clay increase either of 20 percent or more (absolute) within a vertical distance of 7.5 cm or of 15 percent or more (absolute) within a vertical distance of 2.5 cm, in the fineearth fraction. Abruptic Durixeralfs 

JDAF. Other Durixeralfs that have a duripan that is strongly cemented or less cemented in all subhorizons. Haplic Durixeralfs 

JDAG. Other Durixeralfs. Typic Durixeralfs 

Definition of Typic Durixeralfs 

Typic Durixeralfs are the Durixeralfs that: 

1. Have an argillic horizon that meets one or more of the following:

                a. Has less than 35 percent clay in all subhorizons that are 7.5 cm or thicker; or

                b. Has an increase in clay content that is less than 15 percent (absolute) within a vertical distance of 2.5 cm and is less than 20 percent (absolute) within a vertical distance of 7.5 cm at the upper boundary and within all parts; 

2. Do not have, in any subhorizon within the argillic horizon, redox depletions with chroma of 2 or less and also aquic conditions; 

3. Have a duripan that is very strongly cemented or indurated in some part; 

4. Do not have a natric horizon; and 

5. Above the duripan, do not have either:

                a. Cracks that are 5 mm or more wide through a thickness of 30 cm or more for some time in normal years, and slickensides or wedge-shaped aggregates in a layer 15 cm or more thick; or

                b. A linear extensibility of 6.0 cm or more.

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