Rhizoliths, and other distinctive modifications of carbonate soil texture by plant roots, are important for identifying paleosols in the post-Silurian geologic record.
Rock units whose structure and fabric were established largely by the activity of plant roots are called rhizolites.
[1] Colin F. Klappa first proposed the term rhizolith for various organosedimentary structures produced by the activity of plant roots in 1980,[1] and his terminology has since been widely adopted[2] with some extensions.
Closely packed, very thin root moulds give the sediments an alveolar texture.
The cement is typically calcite and is responsible for the preservation of root morphology in otherwise poorly consolidated sediments.
Petrifaction is defined as 'a process of fossilization whereby organic matter is converted into a stony substance by the infiltration of water containing dissolved inorganic matter, such as calcium carbonate and silica, which replaces the original organic material, sometimes retaining the original structure'.
The diameters of rhizoliths range from 0.1–20 millimetres (0.0039–0.7874 in), while the longest reported animal burrow had a width of 0.5 centimetres (0.20 in).
[10] Plant roots normally remove calcium from soil while lowering its pH, by exchanging H+ ions for Ca2+, Mg2+, K+, and other cations.
However, they are limited to post-Silurian beds, since vascular plants with extensive root systems did not flourish until this time.
[3] Unusual rhizoliths from the Lower Cretaceous have provided evidence of the earliest activity of social termites.