A U-Pb age for the Cambrian Taylor Formation, Antarctica: Implications forthe Cambrian time scale

Isotopic ages for the Middle Cambrian-Late Cambrian are few because formati ons of the appropriate age combining diagnostic fossils and rocks datable b y precise isotopic techniques are not common. The Taylor Formation in Antar ctica includes carbonate units that host trilobites, indicating an early la te Middle Cambrian age. Volcanics below and above the trilobite-bearing hor izon yielded zircons that date the horizon at 505.1 +/- 1.3 Ma. This age su ggests that the Middle-Late Cambrian boundary is less than 505 Ma, consiste nt with a similar to 500 Ma boundary and a duration of similar to 10 m.yr. each for the Middle and Late Cambrian.