The Collaborative International Dictionary of English v.0.48:
Superjacent \Su`per*ja"cent\, a. [L. superjacens, p. pr. of superjacere; super above + jacere to lie.] Situated immediately above; as, superjacent rocks. [1913 Webster]WordNet (r) 3.0 (2006):
superjacent adj 1: lying immediately above or on something else [ant: subjacent]