MULTIMETHOD RADIOMETRIC AGE FOR A BENTONITE NEAR THE TOP OF THE BACULITES-REESIDEI ZONE OF SOUTHWESTERN SASKATCHEWAN (CAMPANIAN MAASTRICHTIAN STAGE BOUNDARY)

Authors
BAADSGAARD H LERBEKMO JF WIJBRANS JR SWISHER CC FANNING M
Citation
H. Baadsgaard et al., MULTIMETHOD RADIOMETRIC AGE FOR A BENTONITE NEAR THE TOP OF THE BACULITES-REESIDEI ZONE OF SOUTHWESTERN SASKATCHEWAN (CAMPANIAN MAASTRICHTIAN STAGE BOUNDARY), Canadian journal of earth sciences, 30(4), 1993, pp. 769-775
Citations number
22
Categorie Soggetti
Geosciences, Interdisciplinary
Journal title
Canadian journal of earth sciences → ACNP
ISSN journal
00084077
Volume
30
Issue
4
Year of publication
1993
Pages
769 - 775
Database
ISI
SICI code
0008-4077(1993)30:4<769:MRAFAB>2.0.ZU;2-3
Abstract
A 15 cm thick bentonite at the top of the Baculites reesidei Zone in C ruikshank Coulee north of Herbert in southwestern Saskatchewan yielded biotite, sanidine, plagioclase, and zircon. Rb-Sr analyses give a min eral isochron with an age of 72.5 +/- 0.2 Ma (+/- 2a). U-Pb analyses o f zircon produced concordant Pb-206/U-238 and Pb-207/U-235 ages of 72. 4 +/- 0.4 Ma (+/- 2sigma) and 72.6 +/- 0.4 Ma (+/- 2sigma), respective ly. Laser Ar-40/Ar-39 dating of sanidine and biotite revealed ages of 72.5 +/- 0.2 Ma (+/- SE) and 72.6 +/- 0.2 Ma (+/- SE), respectively. I f the Campanian - Maastrichtian stage boundary is near the top of the Baculites reesidei Zone, then the overall average age of 72.5 +/- 0.4 Ma dates the stage boundary.