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Disappearance of the Earliest Manifestation of Life on Earth –Solved!

The widespread disappearance of stromatolites, the earliest visible manifestation of life on Earth, may have been driven by single-celled organisms called foraminifera. Stromatolites (“layered rocks”) are structures made of calcium carbonate and shaped by the actions of photosynthetic cyanobacteria and other microbes that trapped and bound grains of coastal sediment into fine layers. They showed up in great abundance along shorelines all over the world about 3.5 billion years ago.

“Stromatolites were one of the earliest examples of the intimate connection between biology—living things—and geology—the structure of the Earth itself,” said Woods Hole Oceanographic Institution (WHOI) geobiologist Joan Bernhard, lead author of the study.

The growing bacterial community secreted sticky compounds that bound the sediment grains around themselves, creating a mineral “microfabric” that accumulated to become massive formations. Stromatolites dominated the scene for more than two billion years, until late in the Proterozoic Eon.

“Then, around 1 billion years ago, their diversity and their fossil abundance begin to take a nosedive,” said Bernhard. All over the globe, over a period of millions of years, the layered formations that had been so abundant and diverse began to disappear. To paleontologists, their loss was almost as dramatic as the extinction of the dinosaurs millions of years later, although not as complete: Living stromatolites can still be found today, in limited and widely scattered locales, as if a few velociraptors still roamed in remote valleys.

 

 

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Juni 1, 2013 - Posted by | Presse |

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