Cyclostratigraphic record of the Triassic: a critical examination

Abstract

AbstractHigh frequency (fourth- and fifth-order) cyclicity is a common feature of sedimentary sequences in all depositional settings. While tectonism and autocyclic processes are clearly responsible for this cyclicity in some instances, many cases are interpreted as resulting from orbitally forced variations in solar insolation at the Milankovitch frequencies, that is, the precession and short and long eccentricity cycles at scales of tens of thousands to hundreds of thousands of years. This forcing is presumed to have controlled sedimentation through periodic changes in climate or sea-level. Examples of interpreted Milankovitch-frequency cyclicity occur throughout the Triassic record, and include much of the German Triassic, the Alpine Triassic and the Newark Supergroup of North America. The cyclostratigraphy of these sections has been used as a tool for intrabasinal and interbasinal correlation, and for chronostratigraphy. These interpretations are not always without controversy, however, as conceptual arguments and radio–isotopic age data have called some of these conclusions into question.