Ticket #5827 (new)

Opened 12 days ago

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Reported by: "Snow Joe® Shovel" <SnowJoeSnowShovel@…> Owned by:
Priority: normal Milestone: 2.11
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as of sediment stabilised by the presence of colonies of microbes that secrete sticky fluids or otherwise bind the sediment particles. They appear to migrate upwards when covered by a thin layer of sediment but this is an illusion caused by the colony's growth; individuals do not, themselves, move. If too thick a layer of sediment is deposited before they can grow or reproduce through it, parts of the colony will die leaving behind fossils with a characteristically wrinkled ("elephant skin") and tubercular texture.

Some Ediacaran strata with the texture characteristics of microbial mats contain fossils, and Ediacaran fossils are almost always found in beds that contain these microbial mats. Although microbial mats were once widespread, the evolution of grazing organisms in the Cambrian vastly reduced their numbers. These communities are now limited to inhospitable refugia, such as the stromatolites found in Hamelin Pool Marine Nature Reserve in Shark Bay, Western Australia, where the salt levels can be twice those of the surrounding sea.


The fossil Charniodiscus is barely distinguishable from the "elephant skin" texture on this cast.
The preservation of these fossils is one of their great fascinations to science. As soft-bodied organisms, they would normally not fossilize and, unlike later soft-bodied fossil biota such as the Burgess Shale or Solnhofen Limestone, the Ediacaran biota is not found in a restricted environment subject to unusual local conditions: they were a global phenomenon. The processes that were operating must have been systemic and worldwide. There was something very different about the Ediacaran Period that permitted these delicate creatures to be left behind and it is thought the fossils were preserved by virtue of rapid covering by ash or sand, trapping them against the mud or microbial mats on which they lived. Their preservation was possibly enhanced by the high concentration of silica in the oceans before silica-se

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