What is another word for "stratum"?

Roget's Thesaurus (1911) lists these synonyms for "stratum": accubation, accumbent, all, alluvial, area, azimuth, back, beam, bed, billiard, board, bowling, butte, calm, coat, couch, couchant, course, cover, covering, cricket, croquet, cut, dead, decumbence, decumbency, decumbent, dess, discumbency, down, escarpment, eschar, esplanade, estrade, even, fell, film, flag, flagstone, flake.