Bioturbation

bioturbation -- n. The disturbance of sediment by organisms, e.g. burrows, trails, or complete mixing.
blueschist -- Metamorphic rock formed under great pressures, but not so great temperatures.
brackish -- adj. Slightly salty.

bioturbation The turning and mixing of sediments by organisms.
black smoker A vent on the seafloor from which hydrothermal fluids are emitted.

See also: Calcareous, Stratigraphy, Soil, Sedimentary rock, Sediment