Describing a lithological unit whose age varies from place to place, or a lithological unit (rock formation) which cuts across various times or biostratigraphic zones; time-transgressive: A diachronous sedimentation can be seen in a geological deposit in which a sedimentary rock formation apparently consists of similar material, but varies in age from place to place.

For example, as a shoreline advances or retreats, a succession of continuous deposits representing different environments, such as a beach, shallow water, and deeper water, may be left behind as their ages vary depending on the positions of the shorelines through the various time sequences.