We present new radiometric ages in order to constrain the calibration of the Cretaceous time scale. They have been obtained from volcanic tuffs sampled at Hokkaido (Japan) within the Northwest Pacific marine succession of the Yezo Group, and are compared with ages from the Western Interior and Boreal basins. The good coherency between the U-Pb, Ar-40/Ar-39 and K/Ar chronometers when applied simultaneously and their comparison with previous determinations, argue for the previously proposed global synchronicity of biotic events. The U-Pb ages allow us to identify that a thermal event has affected some of the K/Ar ages through argon diffusion. Furthermore, the very low uncertainties associated with the U-Pb ages argue for the use of this technique for calibrating the geologic time scale. We obtain an age of 84.9 +/- 0.2 Ma from the base of the Campanian, which provides an upper bound for the Santonian-Campanian limit. The Cenomanian-Turonian limit is dated here at 94.3 +/- 0.3 Ma using U-Pb applied to zircons from the North-Pacific basin, and at 94.2 +/- 1.0 Ma using Ar-40/Ar-39 applied to a Western Interior basin tuff. The Albian-Cenomanian is constrained here between 99.7 +/- 03 and 99.7 +/- 1.3 Ma using, the ID-TIMS and LA-ICPMS U-Pb techniques, respectively. The age of 112.6 +/- 1.1 Ma proposed here for the Aptian-Albian limit is supported by both Ar-40/Ar-39 and K-Ar data. Finally, the approach followed here combining the U-Pb and K/Ar and Ar-40/Ar-39 isotopic dating allowed us to limit the systematic biases inherent to each approach. The very low absolute uncertainties associated with the U-Pb ages, further reinforces the use of this technique for calibrating the Cretaceous time scale.
|Titolo:||New U-Pb (ID-TIMS and LA-ICPMS) and Ar-40/Ar-39 geochronological constraints of the Cretaceous geologic time scale calibration from Hokkaido (Japan)|
|Parole Chiave:||Upper Cretaceous; U-Pb; 40Ar/39Ar; K-Ar; Yezo Group; Geologic time scale|
|Settore Scientifico Disciplinare:||Settore GEO/08 - Geochimica e Vulcanologia|
|Data di pubblicazione:||lug-2011|
|Digital Object Identifier (DOI):||10.1016/j.chemgeo.2011.03.009|
|Appare nelle tipologie:||01 - Articolo su periodico|