SUPERPOSITION

Niels Steno stated (1669) that "...at the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed." This statement suggests that the oldest layer occurs at the base (the Precambrian Vishnu Schist) and is overlain by progressively younger rock layers with the 250 Ma Kaibab Limestone at the top.

Photo by Kevin Hefferan

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