Publication Date:
1993-09-03
Description:
An 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 at approximately 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bowring, S A -- Grotzinger, J P -- Isachsen, C E -- Knoll, A H -- Pelechaty, S M -- Kolosov, P -- New York, N.Y. -- Science. 1993 Sep 3;261:1293-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11539488" target="_blank"〉PubMed〈/a〉
Keywords:
*Biological Evolution
;
*Fossils
;
Geologic Sediments/*analysis
;
Isotopes
;
Lead
;
Paleontology/*methods
;
Siberia
;
Silicates
;
Uranium
;
Zirconium
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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