© Ryan C. McKellar
The team analyzed amber samples from almost all well-known amber deposits worldwide. This amber originates from the Cretaceous period, an inclusion of foliage of the extinct conifer tree Parataxodium sp. from the Foremost Formation at Grassy Lake, Alberta, Canada. It is approximately 77 million years old.
Elevated levels of oxygen in the atmosphere may have caused dinosaurs, insects and other organisms to grow to gigantic sizes millions of years ago, according to prevailing theories.
If a new study from scientists at the Universities of Kansas and Alberta is correct, then the atmosphere of the Cretaceous had a relatively low oxygen content - making the high-oxygen theories severely flawed.
"We do not want to negate the influence of oxygen for the evolution of life in general with our study, but the gigantism of dinosaurs cannot be explained by those theories," said study author Ralf Tappert
, from the University of Alberta.
In the study
, which was published in the journal Geochimica et Cosmochimica Acta
, an international team recreated the makeup of the Earth's atmosphere during the last 220 million years by analyzing modern and fossilized plant resins. Fossilized resins, like amber, are just a few of the organic materials capable of holding reliable data on the Earth's geological history over millions of years.
"Compared to other organic matter, amber has the advantage that it remains chemically and isotopically almost unchanged over long periods of geological time," Tappert explained. "During photosynthesis plants bind atmospheric carbon, whose isotopic composition is preserved in resins over millions of years, and from this, we can infer atmospheric oxygen concentrations."