Scientists uncover miscalculation in geological undersea record

Sep 10, 2008

The precise timing of the origin of life on Earth and the changes in life during the past 4.5 billion years has been a subject of great controversy for the past century. The principal indicator of the amount of organic carbon produced by biological activity traditionally used is the ratio of the less abundant isotope of carbon, 13C, to the more abundant isotope, 12C.

As plants preferentially incorporate 12C, during periods of high production of organic material the 13C/12C ratio of carbonate material becomes elevated. Using this principle, the history of organic material has been interpreted by geologists using the 13C/12C ratio of carbonates and organics, wherever these materials can be sampled and dated.

While this idea appears to be sound over the last 150 million years or so, prior to this time there are no open oceanic sediment records which record the 13C/12C ratio, and therefore, geologists are forced to use materials associated with carbonate platforms or epicontinental seas.

In order to test whether platform-associated sediments are related to the global carbon cycle, a paper by University of Miami Professor Dr. Peter K. Swart appears in the Proceedings of the National Academy of Sciences. This paper examines changes over the past 10 million years at sites off the Bahamas (Atlantic Ocean), the Maldives (Indian Ocean), and Great Barrier Reef (Pacific Ocean). The variations in the 13C/12C ratio are synchronous at all of the sites studied, but are unrelated to the global change in the 13C/12C ratio.

It appears that records related to carbonate platforms which are often used throughout the early history of the Earth are not good recorders of the 13C/12C ratio in the open oceans. Hence, the work presented suggests that assumptions made previously about changes in the 13C/12C ratios of carbonate sediments in the geological record are incorrect.

"This study is a major step in terms of rethinking how geologists interpret variations in the 13C/12C ratio throughout Earth's history. If the approach does not work over the past 10 million years, then why would it work during older time periods?" said Swart. "As a consequence of our findings, changes in 13C/12C records need to be reevaluated, conclusions regarding changes in the reservoirs of carbon will have to be reassessed, and some of the widely-held ideas regarding the elevation of CO2 during specific periods of the Earth's geological history will have to be adjusted."

Source: University of Miami

Explore further: NASA balloons begin flying in Antarctica for 2014 campaign

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Scientists make strides in tsunami warning since 2004

11 hours ago

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

12 hours ago

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

Keter
2.3 / 5 (7) Sep 10, 2008
This has potentially huge impact on our understanding of the CO2 related cycles on this planet, and may definitely change our current concept of "global warming."
Velanarris
2.3 / 5 (3) Sep 10, 2008
This has potentially huge impact on our understanding of the CO2 related cycles on this planet, and may definitely change our current concept of "global warming."


Agreed. It will be interesting to find out if previous estimates of CO2 ratios higher than 500ppm are accurate, an over-estimate, or an under-estimate. I would lean towards an under estimate simply due to the volcanism of the past and the incredible sizes of the megaflora from that time, but in all honesty, who knows.
Excalibur
not rated yet Sep 11, 2008
Nope; none of this has any relevance to radiative forcing.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.