Cycles with Million-Year Episodicities

Abstract

A wealth of stratigraphic data has accumulated for cycles having durations and episodicities of a few million years. They have been recorded in a wide variety of Phanerozoic basins in many different tectonic settings. They constitute the main basis of the Exxon global cycle charts, where they are termed “third-order cycles” (Haq et al., 1987, 1988a). A small selection of these is described in this chapter in order to illustrate stratigraphic patterns and their reflection of tectonic setting. Sequence concepts have also been applied to the study of the Precambrian record (e.g., Christie-Blick et al., 1988), but this work is not discussed here because at this time the record is fragmentary and regional correlations are very limited.