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The Boring Billion

Sedimentary rocks such as these hold the key to understanding variations in ocean trace elements and atmospheric oxygen.

Sedimentary rocks such as these hold the key to understanding variations in ocean trace elements and atmospheric oxygen.

By Ross Large

Trace element levels in the ocean over the past 3.5 billion years explain important evolutionary events such as the Cambrian explosion of life and a “boring” billion years when evolution stood still.

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Four years ago I was sitting at a research seminar listening to one of my colleagues talk about the chemistry of the ancient oceans. He was discussing how a group of scientists in the USA had used computer models to predict the trace element chemistry of oceans 1–2 billion years old.

The idea flashed into my mind that we have the technology in our research laboratory to actually measure trace elements in the ancient oceans using the rock record. It was one of those rare light bulb moments in science that are few and far between.

At that time I was heading a team of scientists studying the chemistry of pyrite in gold ore deposits. We were mapping the trace element variations in pyrite in micron detail in order to understand the chemical history of the fluids that formed the gold ore deposit.

My eureka moment was realising that if we could track the history of trace elements in ancient ore fluids then we should also be able to track the chemistry of the ancient oceans by analysing sedimentary pyrites that formed on the ancient sea floor. The only problem was that we would need to analyse thousands of sedimentary pyrites from all around the world in rocks ranging back to 3.5 billion years ago.

So we formulated the Trace Elements in the Oceans (TEO) project. Our aim was to track the changes in 25 trace elements in the oceans from 3.5 billion...

The full text of this article can be purchased from Informit.