Abstract

A recent proposal for a surge in Cretaceous sea-floor spreading rates caused us to examine the basis for a Cretaceous absolute time scale, because spreading-rate calculations depend on the absolute ages assigned to stratigraphic (fossil) ages of submarine magnetic anomalies. Published estimates of Cretaceous spreading rates are based on Harland and others' (1964) Phanerozoic Time-Scale (PTS), which, because of poor absolute-age control, arbitrarily divides the Cretaceous into stages of equal duration. If another apparently permissible Cretaceous time scale is used, the proposed spreading surge can be nearly erased. We conclude that Cretaceous spreading rates will not be finally established until the Cretaceous time scale is more precisely calibrated to absolute time.

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