Tag: period

A geologic period is a time unit subdivision of geologic time defined as a span of years into which the larger era time units are divided into smaller timeframes, as era’s divide the eon. In the Earth Sciences rocks and especially the sequences of rocks called stratum (plural: strata) arrayed in a ordered “rock column” occurring during a timespan are the focus of study so the time units are paired with corresponding Rock strata units whose characteristics define such points elsewhere that occurred concurrently as the local rock layers were laid down as sediments. For the Geological Period the paired rock strata term, a geologic stage is used to denote the corresponding rock layers of both the geologic record and the fossil record; thus the rocks of the Devonian System were laid down during the Devonian Period, and such equivalent units exist at each level of refinement of geological chronology and biogeological or stratigraphic classification.
Each unit, of strata no matter how…