Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microfossils challenge prevailing views of the effects of 'Snowball Earth' glaciations on life

28.05.2009
New fossil findings discovered by scientists at UC Santa Barbara challenge prevailing views about the effects of "Snowball Earth" glaciations on life, according to an article in the June issue of the journal Nature Geoscience.

By analyzing microfossils in rocks from the bottom of the Grand Canyon, the authors have challenged the view that has been generally assumed to be correct for the widespread die-off of early life on Earth.

"Snowball Earth" is the popular term for glaciations that occurred between approximately 726 and 635 million years ago and are hypothesized to have entombed the planet in ice, explained co-author Susannah Porter, assistant professor of earth science at UCSB.

It has long been noted that these glaciations are associated with a big drop in the fossil diversity, suggesting a mass die-off at this time, perhaps due to the severity of the glaciations. However, the authors of the study found evidence suggesting that this drop in diversity occurred some 16 million or more years before the glaciations. And, they offer an alternative reason for the drop.

A location called the Chuar Group in the Grand Canyon serves as "one of the premier archives of mid-Neoproterozoic time," according to the article. This time period, before Snowball Earth, is preserved as a sort of "snapshot" in the canyon walls.

The scientists found that diverse assemblages of microscopic organic-walled fossils called acritarchs, which dominate the fossil record of this time, are present in lower rocks of the Chuar Group, but are absent from higher strata. In their place, there is evidence for the bacterial blooms that, the authors hypothesize, most likely appeared because of an increase in nutrients in the surface waters. This process is known as eutrophication, and occurs today in coastal areas and lakes that receive abundant runoff from fertilizers used in farming.

"One or a few species of phytoplankton monopolizes nutrients at the expense of others," said Porter, explaining the die-off of diverse acritarchs. "In addition, the algal blooms result in high levels of organic matter production, which we see evidence of in the high organic carbon content in upper Chuar Group rocks. In fact, the organic carbon content is so high in the upper Chuar Group, oil companies were interested in the Chuar Group as a possible source of oil and natural gas." As a result of high levels of organic matter, oxygen levels in the water can become depleted, resulting in widespread "dead zones." Porter and colleagues also found evidence for extreme anoxia in association with the bacterial blooms.

In an accompanying article describing the process of discovering the microfossils, Porter described a highlight of the trip, "…when we rode through the rapids and descended into 'Powell's bowels' –– where the oldest rocks in the Grand Canyon frame the river passage. These rocks formed deep in the Earth approximately 1.8 billion years ago, and are very different in appearance from the overlying rocks."

The scientists braved extreme sun, rattlesnakes, scorpions, and dehydration to gather their data. They traveled by foot, helicopter, and river rafts, the last of which capsized on one occasion –– although the samples remained intact.

The first author on the paper is former UCSB graduate student Robin Nagy, who did the research as part of her work to obtain her master's degree. Nagy now teaches seventh and eighth grade science at Williams Elementary Middle School in Williams, Arizona. Other co-authors are Carol M. Dehler of Utah State University, and Yanan Shen of the University of Quebec.

Gail Gallessich | EurekAlert!
Further information:
http://www.ucsb.edu

More articles from Earth Sciences:

nachricht Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation

nachricht NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>