Age of Matuyama-Brunhes boundary constrained by U/Pb zircon dating of a widespread tephra

The youngest geomagnetic polarity reversal, the Matuyama-Brunhes boundary (MBB), provides an important datum plane for sediments, ice cores, and lavas. Its frequently cited age of 780 ka is based on orbital tuning of marine sedimentary records, and is supported by 40Ar/39Ar dating of Hawaiian lavas...

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Bibliographic Details
Published in:Geology (Boulder) 2015-06, Vol.43 (6), p.491-494
Main Authors: Suganuma, Yusuke, Okada, Makoto, Horie, Kenji, Kaiden, Hiroshi, Takehara, Mami, Senda, Ryoko, Kimura, Jun-Ichi, Kawamura, Kenji, Haneda, Yuki, Kazaoka, Osamu, Head, Martin J
Format: Article
Language:English
Subjects:
absolute age
Ar/Ar
Asia
basins
Brunhes Chron
calibration
Cenozoic
chemostratigraphy
Chiba Peninsula
chronostratigraphy
dates
Far East
fore-arc basins
Geochronology
Geomorphology
Honshu
ice cores
igneous rocks
ion probe data
isotope ratios
Isotopes
Japan
Lava
magnetostratigraphy
Marine
marine sediments
mass spectra
Matuyama Chron
nesosilicates
O-18/O-16
orthosilicates
oxygen
paleomagnetism
pyroclastics
Quaternary
Quaternary geology
Sediments
SHRIMP data
silicates
spectra
stable isotopes
stratigraphic boundary
Stratigraphy
tephrochronology
U/Pb
upper Cenozoic
upper Quaternary
volcanic rocks
zircon
zircon group
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Summary:The youngest geomagnetic polarity reversal, the Matuyama-Brunhes boundary (MBB), provides an important datum plane for sediments, ice cores, and lavas. Its frequently cited age of 780 ka is based on orbital tuning of marine sedimentary records, and is supported by 40Ar/39Ar dating of Hawaiian lavas using recent age calibrations. Challenging this age, however, are reports of younger astrochronological ages based on oxygen isotope stratigraphy of high-sedimentation-rate marine records, and cosmogenic nuclides in marine sediments and an Antarctic ice core. Here, we present a U-Pb zircon age of 772.7± 7.2 ka from a marine-deposited tephra just below the MBB in a forearc basin in Japan. U-Pb dating has a distinct advantage over 40Ar/39Ar dating in that it is relatively free from assumptions regarding standardization and decay constants. This U-Pb zircon age, coupled with a newly obtained oxygen isotope chronology, yields an MBB age of 770.2 ± 7.3 ka. Our MBB age is consistent with those based on the latest orbitally tuned marine sediment records and on an Antarctic ice core. We provide the first direct comparison between orbital tuning, U-Pb dating, and magnetostratigraphy for the MBB, fulfilling a key requirement in calibrating the geological time scale.
ISSN:0091-7613
1943-2682
DOI:10.1130/G36625.1