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Most stromatolites are spongiostromate in texture, having no recognisable microstructure or cellular remains. A minority are porostromate , having recognisable microstructure; these are mostly unknown from the Precambrian but persist throughout the Palaeozoic and Mesozoic .
"Porostromate microstructures are defined by the growth of loose or tangled, vertical, flabellate or flat-lying, straight or sinuous calcified filaments or threads, or even of calcified unicells." Porostromate stromatolites and oncolites are mostly absent throughout the Proterozoic , with calcified filaments apparently first appearing in the ...
"Spongiostromate microstructures result from the individualization of micritic, spongious, fenestral, sparitic, pelloidal, detrital, etc. laminae or films, variously grouped and organized. "Throughout geologic history, spongiostromate stromatolites and oncolites have always seemed to vastly outnumber the porostromate forms. [1]
Ancient giant stromatolites used to be widespread in Earth’s Precambrian era, which encompasses the early time span of around 4.6 billion to 541 million years ago, but now they are sparsely ...
Its base is delimited by a stromatolite bed. Below the Guelph is the Eramosa Formation. This formation is typically a thinly laminated packstone and grainstone. There are stromatolite beds as well as corals preserved in this formation. Near the base the unit becomes vuggy. Again the top of this formation is marked by a sharp change between ...
Stromatolites typically consist of filamentous microfossils. [17] The oldest stromatolites have been dated to approximately 3.5 billion years old. [18] Stromatolites in Barberton have been dated to about 3.3 billion years. Microfossils found in chert extend the Barberton microfossil record back to 3.5 billion years. All three types of ...
The Gunflint Chert is composed of biogenic stromatolites. [3] At the time of its discovery in the 1950s, it was the earliest form of life discovered and described in scientific literature, as well as the earliest evidence for photosynthesis. [4] The black layers in the sequence contain microfossils that are 1.9 to 2.3 billion years in age.
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