super 40 Ar/ super 39 Ar ages from the rhyolite of Alder Creek, California; age of the Cobb Mountain normal-polarity subchron revisited.
Turrin, Brent D; Donnelly, Nolan Julie M; Hearn-B-Carter Jr. (1994) super 40 Ar/ super 39 Ar ages from the rhyolite of Alder Creek, California; age of the Cobb Mountain normal-polarity subchron revisited. Geology Boulder. 22; 3, Pages 251-254. 1994.
| Authors | Turrin, Brent D; Donnelly, Nolan Julie M; Hearn-B-Carter Jr. |
|---|---|
| Year | 1994 |
| Title | super 40 Ar/ super 39 Ar ages from the rhyolite of Alder Creek, California; age of the Cobb Mountain normal-polarity subchron revisited. |
| Source | Geology Boulder. 22; 3, Pages 251-254. 1994. |
| Publisher | Geological Society of America GSA. Boulder, CO, United States. 1994. |
| Document type | Serial |
| ISSN | 0091-7613 |
| GeoRef | 1994-025511 |
| Keywords | absolute-age; Alder-Creek; alkali-feldspar; Ar-Ar; California-; Cenozoic-; Cobb-Mountain; Cobb-Mountain-Subchron; dates-; feldspar-group; framework-silicates; Neogene-; Pliocene-; sanidine-; silicates-; Tertiary-; United-States |
| DOI | 10.1130/0091-7613(1994)022<0251:AAAFTR>2.3.CO;2 |
Abstract
New super 40 Ar/ super 39 Ar age determinations on sanidine from the rhyolite of Alder Creek, California, indicate a 1.186+ or -0.006 Ma age for the Cobb Mountain Normal-Polarity Subchron. The new age is statistically older alpha = 0.05 than the previously reported K-Ar age 1.12+ or -0.02 Ma and agrees with the age suggested by the astronomical polarity time scale. Incomplete extraction of radiogenic super 40 Ar super 40 Ar* from the sanidine is the most likely reason for the disparity between the super 40 Ar/ super 39 Ar and K-Ar ages. Because the Cobb Mountain subchron is a worldwide, short-duration event, and because no widely used interlaboratory super 40 Ar/ super 39 Ar standard younger than 27 Ma exists, we propose that sanidine from the rhyolite of Alder Creek be considered for use as a new Quaternary super 40 Ar/ super 39 Ar mineral standard.
1 sample from this reference
| Sample | Rock name | Major | Trace | Isotope |
|---|---|---|---|---|
| KA3154 | Rhyolite |