Banded Iron Formations And The

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change was brought about by the emergence of cyanobacteria which had adapted to create energy from the sun by photosynthesis(probably due to a shortage of raw materials for energy), as a result they had began to poison the earlier anaerobic bacteria or archea with their waste product; oxygen.
This essay will focus on the evolution of the atmosphere and its relation to the banded iron formations of the late Precambrian.
Banded Iron Formations
Cloud (1968) calls Banded Iron Formations, rhythmically banded chemical sediments of large, open water bodies that take different aspects but most characteristically consists of alternating layers of iron- rich and iron-poor silica. It is present in some of the oldest volcanic sequences (greenstone belts ca 2800 mya) and is a common sediment type formed until approximately 1800 mya. Although some younger formations with similar structure can be found there is great distinctions between them and the BIF’s of the Precambrian.
The ...

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all scientists have accepted the validity of these observations or of their interpretation, Dimroth and Kimberley(1976) argued that at least some red beds antedate the end of BIF deposition, that Archean granites have paleoweathering profiles indicative of oxic environments, and that oxidised sulphur minerals (sulphates) occur in some of the oldest known sedimentary successions. All of these observations are correct, and we must ask whether they preclude the interpretation of Archean and earliest Proterozoic environments as oxygen poor. Holland (1984) believed the answer to be no. As the formation of red beds and oxidised weathering profiles on granitic substrates requires oxygen, but ...

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