Stromatolites are layered accretionary structures produced by blue-green algae (cyanobacteria). They represent some of the earliest life-forms found on Earth and are created as the algae trapped, bound and cemented sedimentary grains in a shallow water environment. Blue-green algae use water, carbon dioxide and sunlight to create food and as thin layers of sediment (limestone) covered them up, they grew upwards to develop a domed shape as they searched for sunlight to aid photosynthesis.

Stromatolites occurred widely in the Precambrian (600 million years ago), but are rare today. They appear to have a been a popular food source for grazing animals that evolved to eat them! More here.

View thin section

Transmitted light
between crossed polars
Transmitted light
plane polarised

Object movie


Polished slice

through a fossil stromatolite.

Width 20 cm.

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Courtesy of Paul Harrison

Modern stromatolites growing in Hamelin Pool Marine Nature Reserve, Shark Bay, Western Australia

Courtesy of M.C. Rygel

Stromatolites in the Hoyt Limestone (Cambrian) exposed at Lester Park, near Saratoga Springs, New York

More Stromatolites

Click hereRMS-Info-Stromatolite2.html
Rotation point 1RMS-Rotation2-Stromatolite.html
Rotation point 2RMS-Rotation3-Stromatolite.html
Labelled viewsRMS-LabelStill-Stromatolite.html

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