Reconciling astrochronological and 40Ar/39Ar ages for the Matuyama-Brunhes boundary and late Matuyama Chron

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doi: 10.1029/2010GC003203
Author(s): Channell, J. E. T.; Hodell, D. A.; Singer, B. S.; Xuan, C.
Author Affiliation(s): Primary:
University of Florida, Department of Geological Sciences, Gainesville, FL, United States
University of Cambridge, United Kingdom
University of Wisconsin-Madison, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, Vol.11. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 75 refs.; illus., incl. 2 tables, sketch map
Summary: When five Matuyama-Brunhes (M-B) boundary records from the North Atlantic are placed on isotope age models, produced by correlation of the δ18O record directly or indirectly to an ice volume model, the M-B boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773.1 ka (standard deviation=0.4 kyr), ∼7 kyr younger than the presently accepted astrochronological age for this polarity reversal (780-781 ka). Two recently proposed revisions of the age of the 40Ar/39Ar Fish Canyon sanidine (FCs) standard to 28.201±0.046 Ma and 28.305±0.036 Ma would adjust 40Ar/39Ar ages applicable to the M-B boundary (and other reversals and excursions back to 1.2 Ma) to ages older than the new astrochronological ages by 8-24 kyr. The variables used to construct the ice volume models cannot account for the discrepancy. The FCs standard age that best fits the astrochronological ages is 27.93 Ma, which is within the uncertainty associated with the commonly used value of 28.02 (±0.16) Ma but younger than the recently proposed FCs ages. The EDC2 and EDC3 age models in the Dome C (Antarctic) ice core yield ages of 771.7 ka and 766.4 ka, respectively, for the 10Be flux peak that denotes the paleointensity minimum at the reversal boundary, implying that the EDC2 (rather than EDC3) age model is consistent with the observations from marine sediments, at least close to the M-B boundary.
Year of Publication: 2010
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 03 Geochronology; 24 Surficial Geology, Quaternary Geology; Age; Alkaline earth metals; Antarctic ice sheet; Antarctica; Ar/Ar; Atlantic Ocean; Be-10; Benthic taxa; Beryllium; Brunhes Chron; Cenozoic; Chronology; Dates; Expedition 303; Expeditions 303/306; Geochronology; IODP Site U1308; Ice cores; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Leg 162; Magnetic field; Marine sediments; Matuyama Chron; Metals; Mid-Atlantic Ridge; North Atlantic; Northeast Atlantic; O-18/O-16; ODP Site 980; ODP Site 983; ODP Site 984; Ocean Drilling Program; Oxygen; Paleomagnetism; Planktonic taxa; Quaternary; Radioactive isotopes; Reversals; Reykjanes Ridge; Rockall Bank; Sediments; Shells; Stable isotopes; Upper Cenozoic; Upper Quaternary
Coordinates: N552906 N552906 W0144208 W0144208
N602412 N602412 W0233826 W0233826
N495300 N495300 W0241400 W0241400
Record ID: 2011101842
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