Stromatolite mm 38 Fossil Precambrian Cyanobacteria Stromatolites (2)

Stromatolite Fossil Precambrian Morocco mm 38 x 25 x 12 - gr 11.2. Stromatolite Fossil you will receive is the one of the Photo.
Fossil formed by carpets of algae and cyanobacteria. The layers are visible in the rock. They were buried in volcanic deposits of the Precambrian Era for 600 million years, only to be found near Ait Saoun, Ouarzazate, Morocco.

Stromatolites (from greek στρώμα, stroma, carpet, blanket and λὶθος, lithos, stone) are sedimentary rock structures, looking for streaked thin alternating dark and light bands, belonging to the group not limestones particle biofactured, finely laminated due to the presence of materials deposited by the activity of microorganisms such as photosynthetic benthic prokaryotes (eg calcimicrobi similar to current cyanobacteria) and even microscopic eukaryotic algae. They were among the major causes of the presence of oxygen in Earth's atmosphere and have been the body that has dominated Earth for nearly three billion years.
With the appearance of photosynthesis, oxygen began to accumulate in the atmosphere and this process led at least two important consequences:
- The birth of the aerobic metabolism, ie cellular respiration;
- The formation of the ozone layer, which protects living things from ultraviolet radiation from the sun.
Currently the oxygen constitutes 21% of the atmosphere, and it is believed that about 2 billion years ago has reached a concentration of 1%, ahead of the appearance of the first eukaryotes and allowing them to develop a eukaryotic metabolism.
Stromatolites are formed by periodic entrapment in mucilage produced by blue-green algae and / or bacteria, very fine particulate sediment, composed mainly of carbonate mud.
After the first algal carpet has set the particles of sediment on its gelatinous surface, to be completely covered, the algal filaments grow above and thus form another carpet. This will form a succession of alternating layers of organic substance with other rich sediment. Because of diagenetic processes, rarely are the remains of microalgae and lamination is the only evidence of their activities. The morphology of stromatolites is very variable, from plane-parallel plates to wavy, up to mammellonari and columnar, depending on the type of algae or bacteria that constitute them and on the environmental conditions. In with high energy environment of the waters, the algal mats can form concentric sheaths around objects ("cores") subjected to continuous rolling through the work of waves and currents, giving rise to isolated objects called oncolites, which are a special case of stromatolite.
They are widely distributed across the Precambrian fossils.
Stromatolites over microbial origins date back to ancient ascertained 2.724 billion years ago, new discoveries show strong evidence of microbial stromatolites from activities dating back to about 3.45 billion years ago and in 2016 have been found stromatolites dating back 3,700 million years ago in the region INUA in Greenland. Among the best known, those found in the Gunflint Iron Formation in Canada, dating back to about 2 billion years ago.
Nell'Archeano stromatolites are quite rare and structurally simple; become abundant and diverse in the Proterozoic. Stromatolites diminished permanently about 680 million years ago; there was a modest recovery only in step Cambrian-Ordovician. This decline is attributable to the appearance of the first metazoan grazers and fossatori organisms biotroubled the seabed destroying the texture of the laminae.
In Italy it is quite frequent in the formations of the Lower Cambrian and Triassic of Sardinia in the Alps and the Apennines, in the carbonate platform environment; It has never been reported in the Precambrian era rocks.
Currently stromatolites are formed in marginal marine environments of tidal plain, in the intertidal zone at normal or high salinity but also in subtidal environments of some areas of Australia, Florida, the Bahamas and the Persian Gulf. These facilities are also widely present in lake environment, especially in the temperate-tropical climate, as a product of bacterial activity.
Have an important meaning paleoenvironmental and, at least in the Phanerozoic, they are good indicators of shallow water environments with high environmental stability. The current ones are morphologically different from those of the Proterozoic.

For more about stromatolites and more generally on the carbonate platforms of this planet, we recommend the article "The first forms of life: prokaryotes and stromatolites," published on our site in the space "Naturalist Portal", at this link.