Three Billion-Year-Old Rocks Contain Plankton
Researchers from Japan and the United States have discovered microfossils of plankton in three billion-year-old rocks.
AsianScientist (Jun. 10, 2013) – Researchers from Japan and the United States have discovered microfossils of plankton in three billion-year-old rocks.
“It is surprising to have large, potentially complex fossils that far back,” said Christopher H. House, professor of geosciences, Penn State, and lead author on the study published in Geology.
Professor Kenichiro Sugitani of the Graduate School of Environmental Studies at Nagoya University, Japan first discovered these unusually shaped microfossils embedded in really old marine sediment rocks from the Farrel Quartzite in Western Australia.
To determine if these inclusions were actually biological in origin, the researchers looked at 15 different samples of Farrel Quartzite and determined their stable carbon isotope ratios. The percentage of carbon 13 in the microfossils was indicative of material produced by biological processes. They found that the carbon 13 percentage in the background organic matter in the surrounding rock was different from that of the microstructures.
Isotopic analysis using secondary ion mass spectrometry showed that these inclusions in the rocks were not only biological in origin, but also that they were likely planktonic autotrophs – free-floating, tiny ocean organisms that produce energy from their environment.
“When considered along with published morphological and chemical studies, these results indicate that the Farrel Quartzite microstructures are bona fide microfossils, and support the interpretation that the spindles were planktonic,” the researchers write.
The spindle-shaped microfossils are from 20 to 60 microns in length, about the size of fine sand and within the size range of today’s microplankton.
Dorothy Oehler, a co-author and research scientist at the NASA Johnson Space Center, notes that the spindles appear to be the same as those found in rocks from the Strelly Pool Formation in Western Australia and the Onverwacht Group in South Africa and Swaziland that are both 3.4 billion years old.
“The existence of these microfossils in diverse locations as far back as 3.4 billion years ago suggests that the oceans probably had life in them for a very extended period of time,” said Oehler. “Moreover, this has implications beyond what we have done here, suggesting the evolution of diverse life proceeded quickly.”
Source: Penn State.
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