Tephrochronology is the study and dating of volcanic ash layers (tephra) to create a chronological framework for geological and archaeological events. This method is significant in stratigraphy and archaeology for correlating and dating deposits across wide geographic areas.
Reference: Lowe, D. J. (2011). “Tephrochronology and Its Application: A Review.” Quaternary Geochronology, 6(2), 107-153.