Based on their hypothesis, the researchers expected to see regional variations in plant productivity the amount of new growth produced in an area over time, which is an indirect measure of the amount of plant life in an environment. Forests, savannas and deserts all have different amounts of plant productivity, although those specific ecosystems can't be identified on the basis of plant productivity alone.
The researchers expected to see higher plant productivity for Portugal than for the Morrison Formation, with the lowest productivity in Central Africa.
"Essentially that's what we found," Myers said. "We understand it's tenuous and not a trend, but few places in the world are well-sampled. However, it's still a useful tool for places where all we have are the soil nodules, without well-preserved fauna."
Soil nodules are fairly common, Myers said. They form as a result of seasonally dry conditions and may be preserved in all but the wettest environments. Since they harden into mineralized clods, they are easy to spot and sample as they weather out of ancient soil profiles.
CO2 in ancient calcite nodules offers key to ancient climate
From the analysis scientists can draw a more complete picture of the ancient landscape and climate in which prehistoric animals lived.
"The Jurassic is thought of as very warm, very wet, with lots of dinosaurs," said Myers, research curator for SMU's Shuler Museum of Paleontology. "But we see from our analysis that there was regional variability during the Late Jurassic in the climate and in the abundance of animals across the planet."
The Late Jurassic extended from 160 million years ago to 145 million years ago.
|Contact: Margaret Allen|
Southern Methodist University