magnacycle

The term "magnacycle" in geology refers to very large-scale, repetitive sequences of rock strata, often spanning entire geologic systems. These are essentially larger versions of cyclothems, which are themselves repetitive successions of marine and nonmarine rock layers indicating cyclic depositional environments.1

While cyclothems are typically around 10 meters thick and can be further categorized into minor (thinner, simpler alternations) and megacyclothems (groups of cyclothems), magnacycles represent a much grander scale of repetition, measuring several kilometers in thickness. However, the validity and utility of magnacycles are considered doubtful by some geologists. The study of these cycles helps geologists understand Earth's history, including past climate changes and the processes that shape the lithosphere.123