Comment on 'U-Pb calcite age of the Late Permian Castile Formation, Delaware Basin: a constraint on the age of the Permian-Triassic boundary (?)' by M.L. Becker et al. [Earth Planet. Sci. Lett. 203 (2002) 681-689]

摘要

Becker et al. in their recent paper [1] have proposed a U–Pb calcite age of 251.5±2.8 Ma for the Castile Formation of the Delaware Basin, and infer that the age of the Permian–Triassic boundary should be younger than this age. In addition, Becker et al. imply that U–Pb ages on organic-rich calcite are more accurate than combined U–Pb zircon and Ar/Ar sanidine/biotite ages from volcanic ash falls. I here challenge the accuracy of the Castile Formation calcite age, and in particular, the proposed constraint on the age of the Permian–Triassic boundary.