ABSTRACT: An important innovation in the International Geologic Time Scale 2004 is the use of astronomically forced stratigraphy, or cyclostratigraphy, to define geologic time over 0 to 23.03 Ma, much of it at an unprecedented resolution of 0.02 myr. In addition, ‘floating’ astronomical time scales with 0.10 to 0.40 myr resolution are defined for entire epochs and stages in the Paleogene and all three Mesozoic periods. Some of these calibrations use a new astronomical model with an hypothesized high accuracy over 0-250 Ma. These accomplishments have motivated the International Commission on Stratigraphy to complete a continuous Astronomical Time Scale (‘ATS’) for the past 250 Ma, and to initiate a coordinated prospecting for astronomical-like signals in Paleozoic cyclostratigraphy. Astronomically calibrated geologic time with a 0.02 to 0.40 myr resolution is a major breakthrough for the geosciences. Chronostratigraphy between widely spaced horizons dated with high-precision radioisotope geochronology suffers total loss in precision and accuracy; a continuous ATS between horizons can restore this hard-won precision and accuracy. Consequently, estimates of rates and magnitudes for a wide range of Earth system processes that can be examined only in the context of Earth history, e.g., paleoclimatology, geochronology, geodynamics, structural geology, geochemical cycles and biotic evolution, will be improved up to an order of magnitude over what is possible today.
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