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Most archean stromatolites older than 3.0 Ga are found in Australia or South Africa. Stratiform stromatolites from the Pilbara Craton have been identified in the 3.47 Ga Mount Ada Basalt. [59] Barberton, South Africa hosts stratiform stromatolites in the 3.46 Hooggenoeg, 3.42 Kromberg and 3.33 Ga Mendon Formations of the Onverwacht Group.
Oncoids are unfixed stromatolites ranging in size from a few millimeters to a few centimeters Fossilized stromatolites, about 425 million years old, in the Soeginina Beds (Paadla Formation, Ludlow, Silurian) near Kübassaare, Estonia. Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping ...
The Gunflint Iron Formation is a banded iron formation, composed predominantly of dense chert and slate layers interbedded with ankerite carbonate layers. The chert layers can be subdivided into black layers (containing organic material and pyrite), red layers (containing hematite), and green layers (containing siderite). [5]
Modern stromatolites are relatively small, Hynek said, whereas ancient stromatolites used to grow to 20 feet (6 meters) tall and 16 to 22 feet (5 to 7 meters) wide, he said.
This is a list of all extinct cyanobacteria genera that formed stromatolites. Collenia; Species Time period Location †C. frequens: Late Proterozoic: Australia
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 microfossil morphologies are found in cherts.
The fossils in the Fig Tree Formation are considered some of the oldest known organisms on Earth, and provide evidence that life may have existed much earlier than previously thought. The formation is composed of shales , turbiditic greywackes , volcaniclastic sandstones , chert , turbiditic siltstone , conglomerate , breccias , mudstones , and ...
The stromatolite fossils appear wavy and dome-shaped, are typically 1–4 cm (0.4–1.6 in) high, and were found in iron- and magnesium-rich dolomites that had recently been exposed by melting snow. [39] The surrounding rocks suggest that the stromatolites may have been deposited in a shallow marine environment. [38]