Definition of "subjacent"

In some places, however, quartz reefs, payably auriferous while in Silurian rock, have been followed down to subjacent granite, and have there been found to thin out and become unprofitable […]

1887, R. A. Murray, Victoria. Geology and Physical Geography, page 126

Since the times of the Spanish conquest of the Americas, however, there had always been a subjacent stream of travel literature which had queried the civilizing function of Western penetration of such societies.

2002, Colin Jones, The Great Nation, Penguin, published 2003, pages 194–5