Source : Webster's Revised Unabridged Dictionary (1913)

Superjacent \Su`per*ja"cent\, a. [L. superjacens, p. pr. of
   superjacere; super above + jacere to lie.]
   Situated immediately above; as, superjacent rocks.

Source : WordNet®

superjacent
     adj : lying immediately above or on something else [ant: {subjacent}]