Holy Grail of geology found

[Dover]

Holy Grail of geology found: Measuring elevation over geological eras
New method to measure ancient land elevation developed




November 29, 2004
Monday


Field Museum scientist has developed a novel way to determine land elevation as continents moved around the Earth through geological ages. Knowing how high mountains and plateaus were in the past will help scientists to study how our climate system evolved. "Understanding the past elevation of land surfaces, also known as paleoelevation, has been one of geology's Holy Grails," said Jennifer McElwain, PhD, Associate Curator of Paleobotany at Chicago's Field Museum and sole author of the research to be published in Geology's December issue. "This is the first paleobotanical method that works globally and is independent of long-term climate change.

"The new method will help us to understand the rate at which some of the Earth's most important mountains have uplifted," she added. "It will also show how the process of mountain building influenced climatic patterns as well as plant and animal evolution."

The new method of paleoelevation involves counting the stomata on leaves of plants going back as far as 65 million years ago. Stomata are minute openings on the surface of leaves through which plants absorb gases, including carbon dioxide, which plants need for photosynthesis. Anyone who has climbed a mountain knows that the air gets "thinner" as you climb higher. As with oxygen, carbon dioxide is less concentrated at higher elevations. Therefore, the higher the elevation, the more stomata per square inch of leaf surface a plant would need to survive. By simply counting the number of fossil stomata, Dr. McElwain can estimate how much carbon dioxide was in the air when the fossil leaf developed. From that, she can estimate the elevation at which the fossil plant once lived...cont'd

http://www.sitnews.us/1104news/112904/112904_geology.html


Old and new leaves
A 15-million-year-old fossil California Black Oak leaf, on loan from the Paleontological Museum Berkeley to the Field Museum, surrounded by modern California Black Oak leaves.
Photo by John Weinstein, courtesy of The Field Museum

[Ediacara]

1. This sounds like real bad science

1) Fossil leaves MUST be exceptional to see stomata (these are features that are cell sized).

2) Global O₂ and CO₂ levels have fluctuated in the past, often wildly.

3) You need extremely precise age ranges for the fossils to escape point #2.

4) Fossils don't get deposited at the top of mountains; mountains are erosional environments.

[pmbryant]

2. I think you might be being overly harsh

Even if the technique is not perfect, if what it is replacing is even worse, then it certainly could be useful. From reading the article, it sounds like that remains to be seen, but it also sounds like a distinct possibility.

:shrug:

--Peter

[Ediacara]

3. But Peter :-)

Fossils aren't preserved in mountain environments. If she's ever able to find leaves preserved with enough details, I'd imagine she'll find that from the Paleocene to the present, no mountain exceeded 1000 m in elevation.

[pmbryant]

4. I don't see how that makes this technique useless

I would think there would be plenty to be learned about pre-historic elevation data of non-mountain regions.

--Peter

[Ediacara]

5. I didn't say it would be useless, just not very useful

You're right, the elevation of non-mountainous regions would be nice to know, but the "Holy Grail" was knowing all elevations, like mountains, which is just unknowable using this, or any, technique.