Correlation

The process by which stratigraphic units in two or more separated areas are demonstrated or determined to be laterally similar in character or mutually correspondent in stratigraphic position, as based on geologic age (time of formation), lithologic characteristics, fossil content, or any other property of stratum; correlation in the usual or narrowest sense. Unless otherwise stated, the term usually means time-correlation, or the determination of equivalence (in time) of stratigraphic units. (Gary, et. Al., 1972)