Fossilized tree discovered in Peru hints at dramatic environmental change

Researchers on an expedition in Peru on the Central AndeanPlateau discovered a huge fossil tree buried in a grassy plain. Plant fossils from the high-altitude site in southern Peru contain reminders that the Andes Mountain environment changed significantly in the last 10 million years. Interestingly, the changes recorded in these fossils don't mesh with climate models.

Researcher Camila Martinez said that the tree and hundreds of fossilized wood, leaf, and pollen samples were collected during the expedition. The fossils show that they were alive when the ecosystem was more humid than climate models of the past predicted. She said that there is "probably" no comparable modern ecosystem noting the temperatures were higher when the fossils were deposited 10 million years ago.

The researchers found that the anatomy of the petrified wood is very much like wood anatomy in low-elevation tropical forests today. When the fossil trees were alive, the researchers believe that the area was probably only 2000 meters above sea level. Today the plateau lies about 4000 meters above sea level and is an extremely arid climate.

The team says that fossils from the same sites that are 5 million years old confirm that the ecosystem that now dominates the Andes high mountain plateaus had been born. Those younger pollen samples are mostly from grasses and herbs rather than trees. Fossil records from the area tell scientists that the altitude and vegetation change dramatically over a relatively short time.

Researchers say that this supports the hypothesis that the tectonic uplift of the region occurred in rapid pulses. The team also believes that the Andean uplift played a critical role in shaping South America's climate.