Oxygen in ocean spread much earlier than previously thought

New York: Iron-bearing rocks that formed at the ocean floor 3.2 billion years ago carry unmistakable evidence of oxygen, much earlier than previous discoveries reported, a new research has found.

The only logical source for that oxygen could be photosynthesis by living organisms, the researchers said. Until recently,

the conventional wisdom in geology held that oxygen was rare until the "great oxygenation event" 2.4 to 2.2 billion years ago.

The most reasonable candidate for liberating the oxygen found in the iron oxide is cyanobacteria, primitive photosynthetic organisms that lived in the ancient ocean, the researchers said.

The rocks under study, called jasper, made of iron oxide and quartz, show regular striations caused by composition changes in the sediment that formed them.