Mysterious magnetic fossils offer climate signals

There are fossils, found in ancient marine sediments and not made up of a few magnetic nanoparticles, that can tell us a lot about the climate of the past, especially the events of sudden global warming. Now, researchers including doctoral student Courtney Wagner and associate professor Peter Lippert from the University of Utah, have found a way to gather the valuable information in these fossils without crush the scarce samples to a fine powder. Their findings are published in Proceedings of the National Academy of Sciences.

“It’s so much fun to be a part of a discovery like this, something that other researchers can use to study magnetofossils and periods of planetary change,” Wagner says. “This work can be used by many other scientists, both inside and outside of our specialist community. This is very interesting and satisfying.”

The name “magnetofossil” may bring to mind images of the X-Men, but the fact is that magnetofossils are microscopic bacterial iron fossils. Some bacteria produce 1/1000 of a width of hair magnetic particles which, when collected into a chain in the cell, act as a nano-scale compass. The bacteria, known as “magnetotactic bacteria,” can use this compass to align themselves with the Earth’s magnetic field and travel efficiently to their preferred chemical conditions in water.

At some point in Earth’s history, at the beginning and middle of the Eocene Age from 56 to 34 million years ago, some of these biologically produced magnets grew to “large” sizes, around 20 times larger than normal magnetofossils, and including alien shapes such as needles, spindles, spear heads and large bullets. Because the bacteria used their magnetic superstructure to find their preferred levels of nutrients and oxygen in ocean water, and because the large magnetofossils are associated with periods of rapid climate change and temperature elevated globe, they can tell us a great deal about the conditions of the ocean during rapid warming, and in particular how these conditions have changed over time.

Previously, extraction and analysis of these fossils was required by pressing the samples into a fine powder for electron microscopy imaging. “The extraction process can be time consuming and unsuccessful, an electronic microscope can be costly, and sample destruction means they are no longer useful for most other experiments,” Wagner says. “The collection and storage of these samples requires dedicated staff, equipment and design, so we want to store as much material as possible for further analysis.”

So Wagner, Lippert and colleagues, including Ramon Egli from the Central Institute for Meteorology and Geodynamics and John Lascu at the National Museum of Natural History, found another way. Using sediment samples collected in New Jersey, they devised a new method of analysis called FORC (first-order inversion curve) measurements. With these high-resolution magnetic measurements, they found that the magnetic signature of large magnetofossils was unique – enough that the approach could be used in other samples to identify the presence of fossils. “FORC measurements study the reaction of magnetic grains to externally applied magnetic fields, enabling discrimination among different types of iron oxide grains without being seen,” Egli said. .

“The ability to quickly locate large magnetofossil assemblages in the geological record will help identify the origins of these rare magnetofossils,” the researchers write, as well as the ecology of the organisms This is important, Wagner says, since no known organisms produce large magnetofossils today, and we still don’t know what organisms they created in the past “The organisms that made these giant magnetofossils are completely mysterious, but this leaves exciting research avenues open for the future,” says Lascu.

Beyond that, however, the information contained in magnetofossils is helping scientists understand how oceans have responded to climate change in the past – and how the normal ocean could we have to deal with ongoing warming.

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After publication, find the full review here. While the embargo builds on February 1 at 1pm Mountain / 3pm East, the online version can be released anytime during the week in February 1-5.