| Abstract: | New 40Ar/39Ar age determinations on sanidine from the rhyolite of Alder Creek, California, indicate a 1.186 ?? 0.006 Ma age for the Cobb Mountain Normal-Polarity Subchron. The hew age is statistically older (?? = 0.05) than the previously reported K-Ar age (1.12 ?? 0.02 Ma) and agrees with the age suggested by the astronomical polarity time scale. Incomplete extraction of radiogenic 40Ar (40Ar*) from the sanidine is the most likely reason for the disparity between the 40Ar/39Ar and K-Ar ages. Because the Cobb Mountain subchron is a worldwide, short-duration event, and because no widely used interlaboratory 40Ar/39Ar standard younger than 27 Ma exists, it is proposed that sanidine from the rhyolite of Alder Creek be considered for use as a new Quaternary 40Ar/39Ar mineral standard. -Authors |
| Genre: | Article |
| ProdID: | 70017919 |
| Citation Author: | Turrin, B. D.; Donnelly-Nolan, J. M.; Hearn, Jr, B. C. |
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| Citation End Page: | 254 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geology |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | 40Ar/39Ar ages from the rhyolite of Alder Creek, California: age of the Cobb Mountain normal-polarity subchron revisited; 1994; Article; Journal; Geology; Turrin, B. D.; Donnelly-Nolan, J. M.; Hearn, Jr, B. C. |
| Citation Start Page: | 251 |
| Citation Volume: | 22 |
| Citation Year: | 1994 |
| Type: | citation/reference |
| Text: | 40Ar/39Ar ages from the rhyolite of Alder Creek, California: age of the Cobb Mountain normal-polarity subchron revisited; 1994; Article; Journal; Geology; Turrin, B. D.; Donnelly-Nolan, J. M.; Hearn, Jr, B. C. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
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