Abstract

The Late Triassic was a time of major environmental change, yet the precise chronology of events is poorly constrained owing to the nonmarine nature of most preserved Upper Triassic strata and the difficulty in correlating sections. St. Audrie's Bay, southwest England, has been the focus of many studies on this interval of time and is one of the proposed sections for the base Jurassic global stratotype section and point (GSSP). In this study, lacustrine deposits exposed at St. Audrie's Bay have been used to construct a floating astronomical time scale for ∼3.7 m.y. of the Late Triassic based on the recognition of ∼100 k.y. eccentricity cycles in rock color. In addition, we have correlated this time scale with an existing magnetostratigraphy through the same succession and produced an astronomically calibrated record of geomagnetic polarity. Using a novel statistical procedure, we have determined the correlation between this succession and the Late Triassic geomagnetic polarity time scale of the Newark Basin, North America, on which the current (2004) geological time scale is based. Our results show unequivocally that the studied St. Audrie's Bay succession represents part of the Norian and we demonstrate for the first time that cyclostratigraphy can be used in the correlation of Mesozoic strata between North America and Europe.

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