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stromatolite |
Also found in: Dictionary/thesaurus, Wikipedia, Hutchinson | 0.02 sec. |
stromatoliteLayered deposit, mainly of limestone, formed by the growth of blue-green algae (see cyanobacteria). These structures are usually characterized by thin, alternating light and dark layers that may be flat, hummocky, or dome-shaped. Stromatolites were common in Precambrian time (more than 543 million years ago). Some of the first forms of life on Earth are recorded in stromatolites in rocks 3.5 billion years old. Stromatolites continue to form in certain areas today, most abundantly in Shark Bay in western Australia. 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. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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This description is consistent with the stone in the floors within the alcoves at the two ends of the upper-level north hall, which has the appearance of domical stromatolites that have been cut parallel to bedding (Fig. Late-Permian sources of limestone, such as clams and corals, likely were replaced by calcium-depositing stromatolite algae that began to flourish after Permian predators perished, he explains. Visitors can see the unique and captivating Shell Beach, where the "sand" is made of trillions of tiny bivalves, or go to the very salty Hamelin Pool nearby and see the stromatolites. |
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