By IANS,
Washington : Scientists have discovered microscopic, magnetic fossils resembling spears and spindles, among sediment layers deposited during an ancient global-warming event along the Atlantic coastal plain.
The researchers were led by geobiologists from the California Institute of Technology (Caltech) and McGill University.
Fifty-five million years ago, earth warmed by more than nine degrees Fahrenheit after huge amounts of carbon entered the atmosphere over a period of just a few thousand years.
Although this ancient global-warming episode, known as the Paleocene-Eocene Thermal Maximum (PETM), remains incompletely explained, it might offer analogies for possible global warming in the future, according to a Caltech press release.
“Imagine our surprise to discover not only a fossil bloom of bacteria that make iron-oxide magnets within their cells, but also an entirely unknown set of organisms that grew magnetic crystals to giant sizes,” said Caltech postdoctoral scholar Timothy Raub, who collected the samples from an International Ocean Drilling Program drill-core storehouse at Rutgers University in New Jersey.
A typical “giant” spearhead-shaped crystal is only about four microns long, which means that hundreds would fit on the period at the end of this sentence. However, the crystals found recently are eight times larger than the previous world record for the largest bacterial iron-oxide crystal.
According to Dirk Schumann, a geologist and electron microscopist at McGill University and co-author of the study: “It was easy to focus on the thousands of other bacterial fossils, but these single, unusual crystals kept appearing in the background. It soon became evident that they were everywhere.”
In addition to their unusually large sizes, the magnetic crystals occur in a surprising array of shapes. For example, the spearhead-like crystals have a six-sided “stalk” at one end, a bulbous middle, and a sharp, tapered tip at the other end.
Once reaching a certain size, spearhead crystals grow longer but not wider, a directed growth pattern that is characteristic of most higher biological organisms.
Spearheads are not, however, the rarest fossil type in the deposit. That honour belongs to a spherical cluster of spearheads informally dubbed the “Magnetic Death Star” by the researchers. The Magnetic Death Star may have preserved the crystals as they occurred in their original biological structure.
“These fossils may be telling a story of radical environmental transformation: imagine a river like the Amazon flowing at least occasionally where the Potomac is today,” said co-author Robert Kopp of Princeton University,
These findings have been published online this week in the Proceedings of the National Academy of Sciences (PNAS).