Stromatolite

Article By:

Ginsburg, Robert N. Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.661000

A laminated, microbial structure in carbonate rocks (limestone and dolomite rocks). Stromatolites are the oldest macroscopic evidence of life on Earth, at least 3.5 billion years old and they are still forming in the seas. During the approximately 2.5–3 billion years of Earth history before marine invertebrates appeared, stromatolites were the most obvious evidence of life and they occur sporadically throughout the remainder of the geologic record. In Missouri and Africa, stromatolite reefs have major accumulations of lead, zinc, or copper; in other locales, such as Montana, New Mexico and Oman, stromatolites occur within oil and gas reservoirs. For geologists, the shapes of stromatolites are useful indications of their environmental conditions and variations in form and microstructure of the laminations may be age-diagnostic in those most ancient sedimentary rocks that lack invertebrate fossils. See also: Astrobiology; Dolomite rock; Limestone; Paleontology; Sedimentary rocks

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