In a joint project of the University of Michigan, the University of New Hampshire and the Smithsonian Institution, researchers have been analyzing fossils from the badlands of Wyoming found in a distinctive layer of bright red sedimentary rock that was deposited at the boundary between the Paleocene and Eocene epochs---a time of apparent sudden climate change. The researchers described their findings in a paper presented Feb. 16 at the annual meeting of the American Association for the Advancement of Science.
"The interval of Earth history that we're studying is marked by a short-term global warming event thought to have occurred when something triggered the release of methane from methane clathrate---a kind of 'methane ice' found in ocean sediments," said Philip D. Gingerich, professor of geological sciences at the University of Michigan. Within about 10,000 years of peak warming, mammals such as primates and the groups that include horses and deer appeared together for the first time in North America, apparently having crossed land bridges from other continents.
As the warm spell continued, the animals showed an intriguing response: they became smaller. For example, "horses from this period that had been the size of a small dog were reduced to the size of a Siamese cat," Gingerich said. When the climate returned to normal, the animals became normal size again. To understand why dwarf versions of the various animals appeared and then disappeared from the fossil record, Gingerich turned to colleagues at the University of Michigan Biological Station who are studying the effects of elevated carbon dioxide levels---associated with global w
Contact: Nancy Ross-Flanigan
University of Michigan