As the plant material decays, the organic acids exude into the surrounding sand and form a lithic calcareous sand cast about the limb or root.
(the organic acids; exude; into the surrounding sand) (the organic acids; form; a lithic calcareous sand cast about the limb or root)
the organic acids the organic acids
exude form
into the surrounding sand
a lithic calcareous sand cast about the limb or root