Close-up of rhizomorphs with drab haloes in maroon portion of varicolored claystone
Close-up of root structures in maroon part of varicolored
border of every yellowish orange root cast is lined by a "drab halo" of
light olive gray, from which iron minerals were leached. Light olive gray
is apparently the natural color of the clays. Leaching must have occurred
when the iron became reduced, since only reduced iron is readily soluble.
Iron in the unleached portions of the root casts was reoxidized, turning the
clay yellowish orange again. This reveals a complex oxidation-reduction
history for this paleosol. To the right of the penny is a large, dark gray root
structure that was produced by a large plant with deep roots (a tree?).
Dark-colored clay from higher in the soil infiltrated along the root course
as woody tissue decayed upon death of the plant. The smooth, shiny
surfaces throughout this unit are slickensides, possibly formed during
expansion and contraction of the soil during successive wetting and
drying episodes (see additional discussion of slickensides in text).
to full view picture
Return to Technical Discussion