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Calibrating rates of early Cambrian evolutionAn explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began about 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.
Document ID
19940035299
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Bowring, Samuel A.
(NASA Headquarters Washington, DC United States)
Grotzinger, John P.
(NASA Headquarters Washington, DC United States)
Isachsen, Clark E.
(MIT Cambridge, MA, United States)
Knoll, Andrew H.
(Harvard Univ. Cambridge, MA, United States)
Pelechaty, Shane M.
(MIT Cambridge, MA, United States)
Kolosov, Peter
(Yakutian Geoscience Inst. Yakutsk, Russia)
Date Acquired
August 16, 2013
Publication Date
September 3, 1993
Publication Information
Publication: Science
Volume: 261
Issue: 5126
ISSN: 0036-8075
Subject Category
Life Sciences (General)
Accession Number
94A11954
Distribution Limits
Public
Copyright
Other

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