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Science 1 April 2005:
Vol. 308. no. 5718, pp. 59 - 60
DOI: 10.1126/science.1111101
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Perspectives

GEOLOGY:
The Calibration of Ediacaran Time

Alan J. Kaufman

During the Ediacaran Period, Earth's earliest soft-bodied organisms emerged in the oceans. In his Perspective, Kaufman highlights the report by Condon et al., who have analyzed two layers from the Doushantuo Formation of southern China. The resulting dates provide important insights into the rates of geological and evolutionary processes. The first layer (~635 million years ago) is at the base of the Ediacaran, whereas the second (~550 million years ago) may constrain the age of an environmental disaster associated with the rapid diversification of the Ediacara biota that lend their name to the period. However, even with exact dates and clever correlations, the specter of a fragmentary rock record adds uncertainty to our picture of Ediacaran Earth history.

The author is in the Geology Department and the Earth Science Interdisciplinary Center, University of Maryland, College Park, MD 20742, USA. E-mail: kaufman{at}geol.umd.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)