Hot springs microbes hold key to dating sedimentary rocks, researchers say

Scientists studying microbial communities and the growth of sedimentary rock at Mammoth Hot Springs in Yellowstone National Park have made a surprising discovery about the geological record of life and the environment.

Their discovery could affect how certain sequences of sedimentary rock are dated, and how scientists might search for evidence of life on other planets.

“We found microbes change the rate at which calcium carbonate precipitates, and that rate controls the chemistry and shape of calcium carbonate crystals,” said Bruce Fouke, a professor of geology and of molecular and cellular biology at the University of Illinois.

In fact, the precipitation rate can more than double when microbes are present, Fouke and his colleagues report in a paper accepted for publication in the Geological Society of America Bulletin.

The researchers’ findings imply changes in calcium carbonate mineralization rates in the rock record may have resulted from changes in local microbial biomass concentrations throughout geologic history.

A form of sedimentary rock, calcium carbonate is the most abundant mineral precipitated on the surface of Earth, and a great recorder of life.

“As calcium carbonate is deposited, it leaves a chemical fingerprint of the animals and environment, the plants and bacteria that were there,” said Fouke, who also is affiliated with the university’s Institute for Genomic Biology.

The extent to which microorganisms influence calcium carbonate precipitation has been one of the most controversial issues in the field of carbonate sedimentology and geochemistry. Separating biologically precipitated calcium carbonate from non-biologically precipitated calcium carbonate is difficult.

Fouke’s research team has spent 10 years quantifying the physical, chemical and biological aspects of the hot springs environment. The last step in deciphering the calcium carbonate record was performing an elaborate field experiment, which drew water from a hot springs vent and compared deposition rates with and without microbes being present.

“Angel Terrace at Mammoth Hot Springs in Yellowstone National Park is an ideal, natural laboratory because of the high precipitation rates and the abundance of microbes,” Fouke said. “Calcium carbonate grows so fast – millimeters per day – we can examine the interaction between microorganisms and the calcium-carbonate precipitation process.”

The researchers found that the rate of precipitation drops drastically – sometimes by more than half – when microbes are not present.

“So one of the fingerprints of calcium carbonate deposition that will tell us for sure if there were microbes present at the time it formed is the rate at which it formed,” Fouke said. “And, within the environmental and ecological context of the rock being studied, we can now use chemistry to fingerprint the precipitation rate.”

In a second paper, to appear in the Journal of Sedimentary Research, Fouke and colleagues show how the calcium carbonate record in a spring’s primary flow path can be used to reconstruct the pH, temperature and flux of ancient hot springs environments. The researchers also show how patterns in calcium carbonate crystallization can be used to differentiate signatures of life from those caused by environmental change.

“This means we can go into the rock record, on Earth or other planets, and determine if calcium carbonate deposits were associated with microbial life,” Fouke said.

Source: University of Illinois at Urbana-Champaign

Related stories:

Fraud with cultured pearls can be detected
Scientists at the Johannes Gutenberg University Mainz (Germany) advise buyers of cultured pearls to be more vigilant. "In Germany too, we are increasingly seeing Chinese sweet-water cultured pearls being marketed as Japanese, although they actually originate from China," say Dr Dorrit Jacob and Ursula Wehrmeister of the Institute of Geosciences.
Geologists Discover Magma and Carbon Dioxide Combine to Make 'Soda-Pop' Eruption
This discovery overturns a longtime belief by geologists, who thought that carbon dioxide was incapable of dissolving in magma, said Calvin Barnes, professor of geosciences and lead investigator.
Shells - a unique climate archive on the ocean floor
Most people who find a seashell during their summer holiday on the coast will probably not be aware that they have found a unique record of the climate. For Professor Bernd Schöne, however, these hard calcium shells provide a profound insight into the history of our earth and especially into the climate of the past.
Ebb and flow of the sea drives world's big extinction events
If you are curious about Earth's periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits.
New Study Finds Increasing Acidification of Pacific Ocean’s Continental Shelf
An international team of scientists surveying the waters of the continental shelf off the West Coast of North America has discovered for the first time high levels of acidified ocean water within 20 miles of the shoreline, raising concern for marine ecosystems from Canada to Mexico.
Before fossil fuels, Earth's minerals kept CO2 in check
Over millions of years carbon dioxide levels in the atmosphere have been moderated by a finely-tuned natural feedback system— a system that human emissions have recently overwhelmed. A joint University of Hawaii / Carnegie Institution study published in the advance online edition of Nature Geoscience links the pre-human stability to connections between carbon dioxide in the atmosphere and the breakdown of minerals in the Earth’s crust. While the process occurs far too slowly to have halted the historical buildup of carbon dioxide from human sources, the finding gives scientists new insights into the complexities of the carbon cycle.
Chalk one up for coccolithophores
Scientists have feared that gradual acidification of the world's oceans would wreak havoc with organisms that build protective outer shells. But a new finding shows at least three species of coccolithophores -- single-celled algae that are major players in the ocean's cycling of carbon -- are responding to ocean acidification by building thicker cell walls and plates of chalk, contrary to what some recent lab experiments have shown.
Nanobacteria – Are They Alive?
Tiny particles called nanobacteria have intrigued researchers in many ways since their discovery 20 years ago, but perhaps the most controversial question they pose is whether or not they are alive.

News discussion:

Space & Earth science news