Geologist finds clues to ancient chemistry of deep oceans

Queen’s researchers have moved another step closer to explaining changes in the chemistry of the deep oceans – and the sudden appearance of large animal fossils – more than 500 million years ago.

Conducted by Geological Sciences and Geological Engineering professor Guy Narbonne, with an international team of researchers, the study focuses on analyses of iron speciation (iron-bearing minerals that form under different oxygen concentrations) and sulfur isotopes during intense global ice ages. This period is commonly called the “snowball” Earth, 800 to 580 million years ago.

“Our results imply that surface ocean waters of this age were oxygenated, but that deep-sea waters were anoxic (depleted of oxygen) during most of this time,” says Dr. Narbonne, an expert in the early evolution of animals and their ecosystems. The deeper water contained abundant dissolved iron, however – a feature that had not been seen for more than one billion years of Earth history, he adds.

The team’s findings appear on-line in the current edition of Science Express.

The level of dissolved oxygen required for accelerated animal growth did not reach deep-sea waters until about 580 million years ago. This coincided with the first appearance of large, animal-like fossils in deep-water sediments of Newfoundland and northwestern Canada.

In 2002, Dr. Narbonne and his colleagues discovered the world’s oldest complex life forms between layers of sandstone on the southeastern coast of Newfoundland. This pushed back the age of Earth’s earliest known complex life to more than 575 million years ago, soon after the melting of the massive “snowball” glaciers.

The current research team, headed by Donald Canfield from the University of Southern Denmark, also includes: Simon Poulton (Newcastle University), Andrew Knoll (Harvard), Gerry Ross (Kula, Hawaii) and Harald Strauss (Justus-Liebig-Universitat Giessen).