Define skeletal horizon

[lauren-obrien]

The concept of a skeletal horizon is used in the order definitions for Organic and Gley soils but is not defined in text. Milne et al (1995) refers to this document for a definition of the concept.

[utukki]

Skeletal material (> 35% stones by volume) - defined in the SMap data manual and in Webb & Lilburne 4th and 5th level of the classification. It's already added to the glossary.

[lauren-obrien]

Cool - leaving this open until the glossary is finalised and cross-links have been added in text.