Radiocarbon dating paleoclimatology
As snow falls on these ice sheets, it compacts with time, forming distinct depositional layers with each consecutive season of snow accumulation.These layers contain tiny bubbles of gas that hold information about atmospheric conditions at the time the bubbles were last in contact with the surface.Radiogenic dating of these rocks allows geologists to constrain the timing of climatic change.
As the blue-green algae eventually re-established itself, atmospheric oxygen levels began to rise again.
This is thought to be the reason for the banding in the banded iron formations (BIFs).
At first, this oxygen was consumed immediately, but then gradually began to build up in the atmosphere, and that weathering of the iron-rich rocks allowed for iron oxidation, turning these layers of sediment red.
After oxygen built up in the oceans, it eventually became toxic to the blue-green algae, causing a die-off of the organisms, and leading to the deposition of dark, unoxidized layers.
Geologists analyze stratigraphic layers in sedimentary rock, with each layer representing millions to hundreds of millions of years.
The geologists look for clues in not only rock composition and texture, but also changes in organisms preserved as fossils.