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Tibet Was Warmer and Wetter Two Million Years Ago

June 15, 2008

Environment News Service (ENS)
June 12, 2008

TALLAHASSEE, Florida, June 12 (ENS) -- Working 15,000 feet up on the
cold, treeless, rocky desert of the Himalayan-Tibetan Plateau, an
international research team was surprised to find thick layers of
lake sediment filled with plant, fish and animal fossils typical of
lower elevations and warmer, wetter climates.

Back at the U.S. National High Magnetic Field Laboratory at Florida
State University, analysis of carbon and oxygen isotopes in the
fossils has revealed that the animals lived recently in geologic
terms - just two to three million years ago - and their diet was made
up of abundant plants.

The scientists determined that "a drastic climate change" was the
reason for their demise during the late Pliocene era, about two or
three million years ago.
Tibet's Kunlun Mountain Pass Basin where the fossil record shows a
warmer, wetter ecosystem once thrived (Photo courtesy Yang Wang)

The scientific team says that fossil evidence suggests that movements
of the Earth's crust caused the Tibetan Plateau to rise to its
towering current elevations - making it inhospitable to the plants
and animals that thrived there as recently as two million years ago,
not millions of years earlier than that, as geologists previously believed.

"The uplift chronology of the Tibetan Plateau and its climatic and
biotic consequences have been a matter of much debate and speculation
because most of Tibet's spectacular mountains, gorges and glaciers
remain barely touched by man and geologically unexplored," said Yang
Wang, associate professor in the Florida State University Department
of Geological Sciences.

The fossil findings are described in the June 15, 2008 issue of the
peer-reviewed journal "Earth and Planetary Science Letters," online
at: www.elsevier.com/locate/epsl.

Yang co-authored the paper, "Stable isotopes in fossil mammals, fish
and shells from Kunlun Pass Basin, Tibetan Plateau: Paleoclimatic and
paleoelevation implications" with paleontologists from the Natural
History Museum of Los Angeles County, and the Institute of Vertebrate
Paleontology and Paleoanthropology, Chinese Academy of Sciences in Beijing.

The collaborative research project, which since 2004 has featured
summer field study on the remote Tibetan Plateau, is funded by a
grant from the Sedimentary Geology and Paleobiology Program of the
U.S. National Science Foundation.

"So far, my research colleagues and I have only worked in two basins
in Tibet, representing a very small fraction of the Plateau, but it
is very exciting that our work to date has yielded surprising results
that are inconsistent with the popular view of Tibetan uplift," said Yang.

She said the new evidence calls into question the validity of methods
currently used by scientists to reconstruct the past elevations of the region.

"Establishing an accurate history of tectonic and associated
elevation changes in the region is important because uplift of the
Tibetan Plateau has been suggested as a major driving mechanism of
global climate change over the past 50-60 million years," said Yang.

"What's more, the region also is thought to be important in driving
the modern Asian monsoons, which control the environmental conditions
over much of Asia, the most densely populated region on Earth."

This summer, Yang and her colleagues from Los Angeles and Beijing
will return for more fieldwork in areas near the Tibetan Plateau.

"The next phase of our work will focus on examining the spatial and
temporal patterns of long-term vegetative and environmental changes
in and around the region," she said. "Such records are crucial for
clarifying the linkages among climatic, biotic and tectonic changes."
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