How does the author use foreshadowing in Treasure?

On July 15, A.D. 391, Junius Venator and a group of Roman military men are just about to seal the cave that holds a vast array of treasures rescued from the destructive hands of Emperor Theodosius. Centuries later, a team led by Dirk Pitt discovers the single ship that escaped, hundreds of miles north off the coast of Greenland, complete with a map of the burial site..... foreshadowing their quest to find the treasure.