The Collaborative International Dictionary of English v.0.48:

Stratify \Strat"i*fy\, v. t. [imp. & p. p. Stratified; p. pr.
   & vb. n. Stratifying.] [Stratum + -fy: cf. F. stratifier.]
   To form or deposit in strata, or layers, as substances in the
   earth; to arrange in strata.
   [1913 Webster] Stratigraphic