ANCIENT SAP. Amber from France's Oise River basin contains quesnoin, a substance whose precursor is made in abundance by a tree found today only in the Amazon Basin.A. Nel/National Museum of Natural History, Paris

Chemical analyses of amber excavated near Paris suggest that France was covered with a dense tropical forest about 55 million years ago.

Amber is a form of fossilized tree sap. Paleontologists discovered copious deposits of the material in the sediments of the Oise River basin, about 50 kilometers north of Paris, in 1997. Fossils in those strata, which were laid down between 55 million and 53 million years ago, are diverse and exceptionally preserved, says Akino Jossang, a biochemist at the National Museum of Natural History in Paris. More than 300 species of arthropods have been found entombed in the Oise amber.

Jossang and her colleagues measured how samples of the Oise amber absorbed various wavelengths of infrared radiation. Results did not match those for Baltic amber, so the researchers used dichloromethane to extract organic compounds from French amber samples. One of those chemicals—named quesnoin—isn't found in other amber, the team reports in the Jan. 18 Journal of Organic Chemistry.

One precursor of quesnoin, a substance called isoozic acid, is produced in small quantities by several types of plants but in abundance by Hymenaea oblongifolia, a tropical tree that lives only in the Amazon rainforest. Other ancient Hymenaea species are suspected to have produced Dominican amber (SN: 3/30/02, p. 202).

The presence of a presumably tropical plant species in France 55 million years ago, when the region was located at a latitude equal to that of modern-day New Orleans, hints that Earth's climate was much warmer then than it is now.

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