A Triassic, Jurassic and Cretaceous Time Scale

Abstract

We present an integrated geomagnetic polarity and stratigraphic time scale for the Triassic, Jurassic, and Cretaceous Periods of the Mesozoic Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high- resolution ^Ar/^Ar age estimates. This framework involves the observed ties between (1) radiometric dates, biozones, and stage boundaries and (2) between biozones and magnetic reversals on the seafloor and in sediments. Detailed attention is given to chronostratigraphic calibration of stage boundaries using tethyan and boreal biozonations. Interpolation techniques to arrive at a geochronology include maximum likelihood estimation, smoothing cubic spline fitting, and magnetochronology. The age estimates for the 31 stage boundaries (Ma with uncertainty in my to 2 standard deviations), and the duration of the preceding stages (in my) are: