Magnetostratigraphy is a geochronological technique that uses the magnetic properties of rock sequences to establish the age of the rocks. By comparing the recorded magnetic polarity in rock layers with the known geomagnetic polarity timescale, geologists can correlate and date sedimentary and volcanic sequences.
Reference: Opdyke, N. D., & Channell, J. E. T. (1996). “Magnetic Stratigraphy.” Academic Press.