Calibration of the latest Eocene-Oligocene geomagnetic polarity time scale using 40Ar/ 39 Ar dated ignimbrites
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Abstract
A discontinuous record of late Eocene-Oligocene geomagnetic polarity has been determined using high-precision (±<0.15 m.y.) 40Ar/39Ar sanidine dating and a paleomagnetic study of 37-27 Ma ignimbrites in New Mexico, Colorado, and Texas. This record provides age control for several geomagnetic polarity reversals that occurred during three periods of intense ignimbrite volcanism: 36.8-33.5 Ma, 32.7-31.4 Ma, 29.1-26.9 Ma. The relative timing of these polarity reversals permits four possible correlations with the geomagnetic polarity time scale (GPTS). The preferred correlation yields calibration ages for Chron C10R (28.0-29.0 Ma) and Chron C13R (34.4-33.1 Ma) that indicate an Eocene-Oligocene boundary age near 33.4 Ma, some 0.3-0.6 m.y. younger than boundary ages indicated by other recently proposed GPTS calibrations based on terrestrial and marine sedimentary sequences.
Suggested Citation
McIntosh, W.C., Geissman, J.W., Chapin, C., Kunk, M.J., and , C., 1992, Calibration of the latest Eocene-Oligocene geomagnetic polarity time scale using 40 Ar/ 39 Ar dated ignimbrites: Geology, v. 20, no. 5, p. 459-463, https://doi.org/10.1130/0091-7613(1992)020<0459:COTLEO>2.3.CO;2.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Calibration of the latest Eocene-Oligocene geomagnetic polarity time scale using 40 Ar/ 39 Ar dated ignimbrites |
| Series title | Geology |
| DOI | 10.1130/0091-7613(1992)020<0459:COTLEO>2.3.CO;2 |
| Volume | 20 |
| Issue | 5 |
| Year Published | 1992 |
| Language | English |
| Publisher | GSA |
| Contributing office(s) | Eastern Geology and Paleoclimate Science Center, Florence Bascom Geoscience Center |
| Description | 5 p. |
| First page | 459 |
| Last page | 463 |