Bunnsediment

Bunnsediment is a term in sedimentology describing sedimentary deposits that bear the mark of bioturbation by burrowing mammals called bunns. It denotes units where burrows and traces from these animals are abundant, and where organic-rich material from surface litter and dung becomes integrated into the sediment column through repeated reworking.

Formation and characteristics: Bunnsediment forms in wetlands, floodplains, and lake margins where bunn populations are dense. Burrow networks disrupt primary sedimentary fabrics, producing cross-cutting channels and fills. Layering may appear irregular, with lenses of finer or coarser grains corresponding to sediment supply, burrow infill, or seasonal activity. The matrix is often silty to clayey, with elevated organic content and occasional pelletized aggregates from fecal matter. The resulting deposit exhibits strong bioturbation, with preserved burrow fills and surface traces.

Distribution and significance: While not a universal term in mainstream geology, bunnsediment is used in discussions of bioturbation-driven stratigraphy and in ecogeomorphology to illustrate how small-mammal activity alters sediment properties, including porosity, permeability, and fossil content. Dating and interpretation rely on associated organic matter, pollen, and microfossils.

See also: Bioturbation, Burrow structures, Sedimentology, Paleoenvironmental reconstruction.