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]

Abstract

Becker et al. in their recent paper 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.