The age of the Steens reversal and the Columbia River Basalt Group

Chemical Geology
By: , and 



The Columbia River Basalt Group (CRBG) eruptions have a well-defined relative magnetostratigraphy but have not been definitively correlated to the geomagnetic polarity time scale. 40Ar/39Ar ages are presented from lavas erupted in the R0 through N1magnetozones of the CRBG and in the transition between R0 and N0. Four ages from transitionally magnetized lava flows at Steens Mountain, Catlow Peak, and Poker Jim Ridge with a weighted mean age 16.58 ± 0.10 Ma1 and the more precise age 16.654 ± 0.025 Ma of the normally magnetized Oregon Canyon tuff at the top of the Catlow Peak section show that the oldest CRBG magnetozone (R0) correlates with the C5Cr chron. Bayesian statistical analysis applied to data from four flows at Catlow Peak (using the mean age of the Steens reversal) gives a best and preferred age of the Steens reversal of 16.73 + 0.13/−0.08 Ma (95% confidence). Depending on the geomagnetic polarity time scale model, the eruption rate from N0 through R2 (0.34–0.45 Ma in the middle and the bulk of the CRBG emplacement) averaged 0.30–0.41 km3/a and peaked at a rate 1 1/2 to 4 1/2 times higher during R2.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The age of the Steens reversal and the Columbia River Basalt Group
Series title Chemical Geology
DOI 10.1016/j.chemgeo.2010.04.001
Volume 274
Issue 3-4
Year Published 2010
Language English
Publisher Elsevier
Contributing office(s) Geology and Geophysics Science Center
Description 11 p.
First page 158
Last page 168