Intercalate
Intercalate , transitive verb
[Latin intercalatus, past participle of intercalare to intercalate to intercalate; inter between + calare to call, proclaim. See Calendar.]
1.
(Chron.) To insert, as a day or other portion of time, in a calendar.
2.
(Geology) To insert among others, as a verse in a stanza; specif. (Geology), to introduce as a bed or stratum, between the layers of a regular series of rocks.
Beds of fresh-water shells... are intercalated and interstratified with the shale.