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Fossilized stromatolites exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, [13] and branching types. [14] Stromatolites occur widely in the fossil record of the Precambrian but are rare today. [15]
A bioherm is a landform of organic sedimentary rock enclosed or surrounded by rock of different origin. [2] A biostrome is a distinctly bedded or broadly lenticular sedimentary rock landform. [ 3 ] Krumbein additionally used these terms to distinguish different shapes of stromatolites : "Distinctly bedded, widely extensive, blanketlike build ...
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Stromatolites were much more abundant in Precambrian times. While older, Archean fossil remains are presumed to be colonies of cyanobacteria, younger (that is, Proterozoic) fossils may be primordial forms of the eukaryote chlorophytes (that is, green algae). One genus of stromatolite very common in the geologic record is Collenia. The earliest ...
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.
The microbes are photosynthetic; thus stromatolites represent shallow water environments in the fossil record due to their necessity to exist in the photic zone of water bodies. Stromatolites typically consist of filamentous microfossils. [17] The oldest stromatolites have been dated to approximately 3.5 billion years old. [18]
The lack of many well-preserved stromatolites has been proposed as a consequence of ongoing diagenesis during formation. [5] Diagenesis is a weathering process where newly deposited sediments lies on top of the old sedimentary bed, buried and compacted, lithified and uplifted to the surface as sedimentary rocks.
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