Peds in paleosol at top of varicolored claystone unit

View looking down on a bedding surface in the uppermost part of the
varicolored claystone unit, showing ancient soil "peds." The colors have
been enhanced to emphasize the ped outlines. Peds are particles of soil
that behave structurally as units. For example, peds are the units that
move during soil expansion and contraction associated with wetting and
drying. In this example, the olive gray peds apparently grated against
each other, creating wide cracks between them that became filled with
pulverized soil scraped from the edges of the peds. The relatively loose
material in the cracks was stained yellowish gray as iron-bearing soil water
flowed through it, but not through the more solid peds. The presence of
either root structures or peds in any rock demonstrates that it was
subaerially exposed and subjected to pedogenic (soil-forming) processes.

Return to Technical Discussion

Main Menu