Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.
NIH NCI

Site Tools

  • AAAS
  • Subscribe
  • Feedback

Site Search

Search Advanced

Science 17 August 1990:
Vol. 249. no. 4970, pp. 760 - 762
DOI: 10.1126/science.249.4970.760
Prev | Table of Contents | Next

Articles

Single-Crystal 40Ar/39Ar Dating of the Eocene-Oligocene Transition in North America

Carl C. Swisher III 1 and D. R. Prothero 2

1 Berkeley Geochronology Center, 2453 Ridge Road, Berkeley CA 94709
2 Department of Geology, Occidental College, Los Angeles, CA 90041

Explanations for the causes of climatic changes and associated faunal and floral extinctions at the close of the Eocene Epoch have long been controversial because of, in part, uncertainties in correlation and dating of global events. New single-crystal laser fusion (SCLF) 40Ar/39Ar dates on tephra from key magnetostratigraphic and fossilbearing sections necessitate significant revision in North American late Paleogene chronology. The Chadronian-Orellan North American Land Mammal "Age" boundary, as a result, is shifted from 32.4 to 34.0 Ma (million years ago), the Orellan-Whitneyan boundary is shifted from 30.8 to 32.0 Ma, and the Whitneyan-Arikareean boundary is now approximately 29.0 Ma. The new dates shift the correlation of Chron C12R from the Chadronian to within the Orellan-Whitneyan interval, the Chadronian becomes late Eocene in age, and the North American Oligocene is restricted to the Orellan, Whitneyan, and early Arikareean. The Eocene-Oligocene boundary, and its associated climate change and extinction events, as a result, correlates with the Chadronian-Orellan boundary, not the Duchesnean-Chadronian boundary.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Eocene-Oligocene extinction and paleoclimatic change near Eugene, Oregon.
G. J. Retallack, W. N. Orr, D. R. Prothero, R. A. Duncan, P. R. Kester, and C. P. Ambers (2004)
GSA Bulletin 116, 817-839
   Abstract »    Full Text »    PDF »
Magnetostratigraphic Tests of Sequence Stratigraphic Correlations from the Southern California Paleogene.
(2001)
Journal of Sedimentary Research 71, 526-536
Age of the earliest known hominids in Java, Indonesia.
C. Swisher 3rd, G. Curtis, T Jacob, A. Getty, A Suprijo, and Widiasmoro (1994)
Science 263, 1118-1121
   Abstract »    PDF »
Correlating the Eocene Oligocene mammalian biochronological scale from SW Europe with the marine magnetic anomaly sequence.
F. LEVEQUE (1993)
Journal of the Geological Society 150, 661-664
   Abstract »    PDF »
Tephra layers as precise chronostratigraphical markers.
R. W. OB. Knox (1993)
Geological Society, London, Special Publications 70, 169-186
   Abstract »    PDF »
Coeval 40Ar/39Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites.
C. C. Swisher, C. C. Swisher III, J. M. Grajales-Nishimura, A. Montanari, S. V. Margolis, P. Claeys, W. Alvarez, P. Renne, E. Cedillo-Pardoa, F. J-M. R. Maurrasse, et al. (1992)
Science 257, 954-958
   Abstract »    PDF »
Rapid Eruption of the Siberian Traps Flood Basalts at the Permo-Triassic Boundary.
P. R. Renne, P. R. RENNE, and A. R. BASU (1991)
Science 253, 176-179
   Abstract »    PDF »


ADVERTISEMENT
Click Me!

ADVERTISEMENT
Click Me!

To Advertise     Find Products

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