Reducing disparity in radio-isotopic and astrochronology-based time scales of the late Eocene and Oligocene

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doi: 10.1002/2017PA003197
Author(s): Sahy, Diana; Condon, Daniel J.; Hilgen, Frederik J.; Kuiper, Klaudia F.
Author Affiliation(s): Primary:
British Geological Survey, Keyworth, United Kingdom
Utrecht University, Netherlands
Volume Title: Paleoceanography
Source: Paleoceanography, 32(10), p.1018-1035. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 91 refs.; illus., incl. sects., strat. cols., 2 tables, sketch map
Summary: A significant discrepancy of up to 0.6 Myr exists between radio-isotopically calibrated and astronomically tuned time scales of the late Eocene-Oligocene. We explore the possible causes of this discrepancy through the acquisition of "high-precision" 206Pb/238U dating of zircons from 11 volcanic ash beds from the Umbria-Marche sedimentary succession, which hosts the Global Stratotype Section and Point for the base of the Oligocene. Our results indicate that the four 40Ar/39Ar dates from the Umbria-Marche succession, which underpin the late Eocene-Oligocene portion of the Paleogene geomagnetic polarity time scale in the 2012 edition of the Geological Time Scale, are anomalously old by up to 0.5 Myr. Conversely, when integrated with the established magnetic polarity record of the Umbria-Marche succession, 206Pb/238U (zircon) data from this study result in Oligocene magnetic reversal ages that are generally equivalent to those obtained through the tuning of Ocean Drilling Program (ODP) Site 1218 (equatorial Pacific). Furthermore, our results indicate that the late Eocene tuning of ODP Site 1218, and International Ocean Discovery Program (IODP) Sites U1333-1334 (equatorial Pacific), to the 405 kyr eccentricity signal is accurate, at least back to 36 Ma. Propagating the full uncertainty of our radio-isotopic data set and, where appropriate, taking into account locally derived astronomical time scales, we arrive at an age of 34.09 ± 0.08 Ma for the Eocene-Oligocene boundary and 28.11 ± 0.17 Ma for the base of the Chattian. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 03 Geochronology; 12 Stratigraphy, Historical Geology and Paleoecology; Absolute age; Ancona Italy; Cenozoic; Chattian; East Pacific; Eocene; Equatorial Pacific; Europe; Expedition 320; Expeditions 320/321; IODP Site U1333; IODP Site U1334; Integrated Ocean Drilling Program; Italy; Leg 199; Lithostratigraphy; Lower Oligocene; Marches Italy; Massignano Italy; Nesosilicates; North Pacific; Northeast Pacific; ODP Site 1218; Ocean Drilling Program; Oligocene; Orthosilicates; Pacific Ocean; Paleogene; Piobbico Italy; Rupelian; Silicates; Southern Europe; Stratigraphic boundary; Stratotypes; Tertiary; U/Pb; Upper Eocene; Upper Oligocene; Zircon; Zircon group
Coordinates: N103100 N103100 W1382510 W1382510
N080000 N080000 W1315824 W1315824
N085300 N085300 W1352200 W1352200
N433200 N433900 E0133600 E0122800
Record ID: 2017099838
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom