stromatolite


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stromatolite,

layered structures produced by the binding together of sediments by a thin layer of cyanobacteriacyanobacteria
or blue-green algae,
photosynthetic bacteria that contain chlorophyll. For many years they were classified in the plant kingdom along with algae, but discoveries made possible by the electron microscope and new biochemical techniques have shown them to be
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. The layers, which are deposited very slowly, gradually produce rounded or hummocklike formations. Stromatolite fossils are common in Precambrian rocks, and the cyanobacteria associated with them are believed to have been a major contribubutor to the increasing oxygen of the early earth. Stromatolites now are found primarily in environments where high salt levels discourage animals from eating the cyanobacteria.

Stromatolite

 

a dense, layered structure that forms in limestones and dolomites as a result of the presence of colonies of blue-green and other algae. Stromatolites reach several meters in length and 1–2 m in height. They have been traced back to the Proterozoic; Upper Proterozoic and Lower Paleozoic fossils are particularly common. The formation of stromatolites occurs in warm, shallow waters with elevated or decreased salinity. The various morphological types, which evolved during the course of geological time, are used for the biostratigraphic analysis of Upper Proterozoic deposits, in which remains of other organisms are extremely rare.

stromatolite

[strə′mad·əl‚īt]
(geology)
A structure in calcareous rocks consisting of concentrically laminated masses of calcium carbonate and calcium-magnesium carbonate which are believed to be of calcareous algal origin; these structures are irregular to columnar and hemispheroidal in shape, and range from 1 millimeter to many meters in thickness. Also known as callenia.
References in periodicals archive ?
Stromatolites ("layered rocks") are rocky structures made by photosynthetic cyanobacteria.
I took more pictures at the stromatolite beach than anywhere else in Australia.
The most persuasive evidence for microbial life on the early Earth comes from stromatolites as discussed before.
A different model of coastal community dominated by bacteria are the communities dominated by stromatolites.
Microbialites are considered living representatives of ancient stromatolites, which first appeared during the Archaean eon (Allwood, Walter, Kamber, Marshall, & Burch, 2006).
Two main facies have been defined in the stromatolites: light grey microbial stromatolite with generally planar lamination, and crinkle laminated stromatolite beds (Fig.
It is described as deposited in a shallow-marine environment, as indicated by the presence of stromatolites (Hofmann 1974).
It is therefore possible to know the length of day in the past from palaeontological studies of annual and daily growth rings in corals, bivalves, and stromatolite.
Along the shoreline of Laguna Bacalar, a freshwater bay in the Quintanaroo region of Mexico, a field of over 50 stromatolite heads occurs with a growth form that is anomalous to their current freshwater setting.
Small structures, considered to be stromatolites, similar to the laminar and small domal stromatolite Ozarkcollenia, occur in ferruginous Mesoproterozoic bedded tufts of the Cope Hollow Formation near Johnson's Shut-ins, Reynolds County, Mo.