In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age and shorter than a period. We are currently living in the Holocene epoch of theQuaternary period. Rock layers deposited during an epoch are called a series. Series are subdivisions of the stratigraphic column that, like epochs, are subdivisions of the geologic timescale. Like other geochronological divisions, epochs are normally separated by significant changes in the rock layers they correspond to.
Epochs are most commonly used for the younger Cenozoic Era, where a greater collection of fossils have been found and paleontologists have more detailed knowledge of the events that occurred during those times. They are less commonly referred to for the other eras and eons, since less fossil evidence exists that allows us to form a clearer view of those time periods.