Stromatolite Kalkowsky, 1908

DESCRIPTION: Laminated organosedimentary structures formed by the trapping, binding and cementation of sedimentary grains by microorganisms. Morphologies include conical, stratiform, branching, domal, and columnar types.

BEHAVIOR(S): Equilibrichnia

ENVIRONMENTAL SETTINGS: Modern stromatolites are found in shallow marine (e.g., Exuma Cays, The Bahamas) and even deep-water settings (Arabian Sea). Some environments exhibit variable to high salinity that is not conducive to organisms that graze biolaminates. Others are beyond the photic zone and chemoautotrophy is used to construct them. Also found in such freshwater settings as rivers and lakes and in areas of acid mine drainage, where either freshwater, extreme heat, or acidity dominate. Examples of these settings include Western Australia, eastern Africa, and the USA (e.g., Yellowstone National Park, Wyoming, and western Indiana).

POSSIBLE TRACEMAKERS: Consortia of prokaryotes (Archea and Bacteria) and proterozoa and fungii (eukaryotes); produced by movement of microorganisms via phototaxis and chemotaxis as detrital and chemical sediments bury them.

GEOLOGIC RANGE: Archean-recent

REMARKS: Most stromatolites do not contain fossil evidence of the microbial consortia that constructed them. The earliest stromatolites––Archeon––constructed by Archea and primitive Bacteria, such as cyanobacteria. Later stromatolites were produced by more diverse consortia of microbial communities, including eukaryotes.

ADDITIONAL REFERENCES: Himmler et al. 2018, Hasiotis and Brake 2019

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