Researchers discover 'giant' magnetofossils from microorganisms that thrived 55 million years ago

Researchers from McGill University, along with colleagues from the California Institute of Technology, the Curie Institute in Paris, Princeton University and other institutions, have unearthed crystalline magnetic fossils of a previously unknown species of microorganism that lived at the boundary of the Paleocene and Eocene epochs, some 55 million years ago. Their results were published Oct. 21 in the Proceedings of the National Academy of Sciences.

The research might help scientists understand more thoroughly the potential effects of significant changes in the Earth's climate.

Though they are only some four microns long, these newly discovered, spear-shaped magnetite crystals (magnetofossils) - unearthed at a dig in New Jersey - are up to eight times larger than previously known magnetofossils. Magnetofossils are remnants of magnetite crystals produced by a type of bacteria called magnetotactic bacteria that are capable of orienting themselves along the direction of the Earth's magnetic field.

The new fossils are "unlike any magnetite crystal ever described," the study's first author Dirk Schumann - a graduate student at McGill's Department of Earth and Planetary Sciences - told Nature News.

"Previous reports suggested that the source of the magnetic signature in the boundary layer was a type of magnetite that was formed by the impact of a comet," said lead researcher and corresponding author Dr. Hojatollah Vali. "In our previous paper we proved that the magnetic signature comes from biogenic material.

"This is an entirely new class of organism that no one has reported before," explained Vali, a professor jointly appointed in McGill's Departments of Anatomy and Cell Biology and Earth and Planetary Sciences. "When my colleagues and I first discovered magnetofossils in deep-sea sediments in the mid-1980s, we knew already that magnetotactic bacteria produced magnetite and then we looked for the magnetofossils. In our new study, we discovered the magnetofossils first without knowing the organism."

This species of microorganism, explained Vali, lived during a period of abrupt global warming known as the Paleocene-Eocene Thermal Maximum (PETM), when worldwide temperatures rose by 5* to 6* C over a period of 20,000 years.

"What's very interesting is that we know the very specific time frame when these organisms existed," he said. "If you go below it, we don't find them, and if you go above it, we don't find them. Five degrees warmer may not seem like much, but there was much more iron available due to increased weathering. The additional iron is required for the microorganism to produce the giant magnetofossils. It is clear that a similar abrupt global warming climatic event could have a severe impact upon our biosphere."