Eonothem
![Horseshoe Canyon Formations exposed in Horseshoe Canyon near Drumheller, Alberta.](/Images/godic/202501/11/Horseshoe_Canyon_Alberta_Nov_19885359.jpg")
![Oxfordian (Upper Jurassic) cyclic sediments at Péry-Reuchenette, near Tavannes, kanton Bern, Switzerland. Alternating layers are limestone (light, more competent) and marl/clay; dominant cycle is the 200000 year-cycle.](/Images/godic/202501/11/Péry-Reuchenette_Oxfordian5400.JPG")
In stratigraphy and geology, an eonothem is the totality of rock strata laid down in the stratigraphic record deposited during a certain eon of the continuous geologic timescale. The eonothem is not to be confused with the eon itself, which is a corresponding division of geologic time spanning a specific amount of (millions of) years, during which rocks were formed that are classified within the eonothem. In practice, the rock column is discontinuous: