Stromatolites

 

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 polarshttp://www.open.ac.uk/earth-research/tindle/AGT/mosaics/zgoogle_11agt37_xpl/index.html
Transmitted light
plane polarisedhttp://www.open.ac.uk/earth-research/tindle/AGT/mosaics/zgoogle_11agt37_ppl/index.html

Object movie

Specimen
rotationRMS-Object-Stromatolite.html

Polished slice

through a fossil stromatolite.

Width 20 cm.

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Courtesy of Paul Harrisonhttp://en.wikipedia.org/wiki/File:Stromatolites_in_Sharkbay.jpg

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

Courtesy of M.C. Rygelhttp://en.wikipedia.org/wiki/File:Stromatolites_hoyt_mcr1.JPG

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
http://www.virtualmicroscope.co.uk/home

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