Microbially-Induced Sedimentary Structures

Microbialite: a rock formed via the influence of microbial trapping, binding, and precipitation Microbial assemblages (in biofilms) form sticky films that influence sediment deposition Microbially-bound sediments are stabilized and more cohesive

Trapping, binding by bacteria Micritization welds grains together Sediment Influx Trapping, binding by bacteria Micritization welds grains together Decay of heterotrophic bacteria increases alkalinity, favoring precipitation Early cementation critical for growth of microbialites Aragonite precipitation beneath biofilm

Stromatolite: laminated organosedimentary structure created by trapping and binding of sediment by a microbial biofilm

Thrombolite: clotted, non-laminated microbialite Require lower sediment influx, form in subtidal environments

Microbialites in siliciclastics (e. g Microbialites in siliciclastics (e.g., “wrinkle structures”) do not form structures with relief above seafloor, likely due to lack of carbonate precipitation Wrinkle Structures, Lower Cambrian