Single-crystal sup 40 Ar/ sup 39 Ar dating of the Eocene-Oligocene transition in North America

Journal Article · Fri Aug 17 00:00:00 EDT 1990 · Science (Washington, D.C.); (USA)

DOI:https://doi.org/10.1126/science.249.4970.760· OSTI ID:6263789

Swisher, III, C C ^[1]; Prothero, D R ^[2]

---

1. Berkeley Geochronology Center, CA (USA)
2. Occidental College, Los Angeles, CA (USA)

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) {sup 40}Ar/{sup 39}Ar dates on tephra from key magnetostratigraphic and fossil-bearing 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. 30 refs., 1 fig., 1 tab.

• OSTI ID: 6263789
• Journal Information: Science (Washington, D.C.); (USA), Journal Name: Science (Washington, D.C.); (USA) Vol. 249:4970; ISSN SCIEA; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540140 -- Environment
Atmospheric-- Thermal Effluents Monitoring & Transport-- (1990-)
540240* -- Environment
Terrestrial-- Thermal Effluents Monitoring & Transport-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
AGE ESTIMATION
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CENOZOIC ERA
CRYSTALS
DATA
EOCENE EPOCH
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
GEOLOGIC AGES
INFORMATION
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MONOCRYSTALS
NUCLEI
NUMERICAL DATA
PLANTS
RADIOISOTOPES
STABLE ISOTOPES
TERTIARY PERIOD
YEARS LIVING RADIOISOTOPES