Note that to calculate an age using this technique the ratio of uranium-234 to its parent isotope uranium-238 must also be measured.
However, magma chamber process and history of Bishop Tuff are too complex to obtain accurate zircon ages by U–Pb method.
To overcome this, therefore, the Th–Pb zircon dating method is a key technique for understanding complex, pre-eruptive magma processes, and further efforts to improve its precision and accuracy are desirable. Although carefully collected, accuracy cannot be guaranteed. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
Pleistocene extinction of Genyornis newtoni: human impact on Australian megafauna.
Non-destructive gamma spectrometric U-series dating.
The resulting correction factors are ƒTh/U = 0.19 ± 0.14 and ƒPa/U = 3.66 ± 0.89 (Kirigamine Rhyolite), ƒTh/U = 0.24 ± 0.20 and ƒPa/U = 3.1 ± 1.2 (Bishop Tuff), and ƒTh/U = 0.28 ± 0.17 and ƒPa/U = 3.04 ± 0.99 (Toga Pumice).
Although the uncertainties of these f values are relatively large, our results support the adequacy of the conventional approach for correction of initial disequilibrium.Conventionally, the initial disequilibrium for the ²³⁸U and ²³⁵U decay series has been determined by the distribution ratio between the melt and zircon (i.e., ƒTh/U = (Th/U)Zircon/(Th/U)Melt and ƒPa/U = (Pa/U)Zircon/(Pa/U)Melt).In our study, these correction factors were determined from comparison of the measured ²³⁸U–²⁰⁶Pb and ²³⁵U–²⁰⁷Pb ages with ²³²Th–²⁰⁸Pb ages obtained for three zircons of known eruption and, in some cases, zircon crystallization ages (Kirigamine Rhyolite, Bishop Tuff, and Toga Pumice). The contributions of uranium/thorium and marine palynology to the dating of the Lake Wangoom pollen record, western plains of Victoria, Australia. 230Th/234U and 14C dating of a late Pleistocene stalagmite in Lobatse II cave, Botswana. U-Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years.