The ocean used to have very little oxygen

The existence of special minerals in ancient coral reefs shows that 650 million years ago, Earth's oceans had very little oxygen, according to Australian researchers on August 17.

"This is really interesting, because this is the time when multicellular animals start to grow," said graduate student Ashleigh Hood of the University of Melbourne, Australia.

According to researchers, the ocean used to have very little oxygen

Hood said their team studied rock masses taken from the Adelaide belt in South Australia. This is a cluster of rocks dating back 500-800 million years, formed when Earth's tectonic plates repel each other.

The team found dolomite - a cement-like compound, and a large amount of iron in these rocks.

'The mineral dolomite itself also has a lot of iron. This suggests that iron was once present in Earth's oceans - Hood said - And the only time you get dissolved iron in the ocean is when it doesn't have oxygen, because otherwise it will form sediment. ' .

According to Hood, it seems that the flow of the ocean is stopped or slowed down during the cold period 650 million years ago, and this leads to low or no oxygen.