Rhizoliths

Rhizoliths are mineralized records of plant roots preserved in sedimentary rocks and soils. They occur when mineral-rich fluids migrate through buried root channels, precipitating minerals that fill or replace the original root tissue, or when minerals cement around an emptied root trace to form a durable cylinder that mirrors the root system.

Two main forms are recognized: rhizoliths formed by replacement, where the root tissue is chemically replaced by minerals (such as calcite, silica, or dolomite) and often preserves internal features of the root; and rhizoliths formed as casts or molds, where the decayed root leaves a void that is later filled by minerals, yielding a hollow or partially filled tube. In practice these processes can occur together, producing a variety of textures.

Rhizoliths are common in paleosols and in carbonate-rich sediments, particularly in arid and semiarid environments where root channels are preserved and diagenesis can cement them. They are found in both ancient rocks and, in some cases, modern soils, where active root channels may become mineralized over time.

Significance: Rhizoliths provide indirect evidence of past vegetation, rooting depth, soil formation, and hydrological conditions. Their presence can aid reconstruction of paleoenvironments, climate, and stratigraphic interpretation.

See also: root casts, paleosol, permineralization, diagenesis.