Calvin,
You remember hearing/reading somewhere about the Magi Slation who lived in this area used that mark. In fact it was hinted at more then once that he is responsible for the existence of this town.
Some stories say he created it himself, others say he "set up shop" near here and a town grew out of that, or other various reasons. But the common thread is that this town most likely wouldn't of existed if wasn't for Magi Slation.
(ooc: I think I'm going to start using Magi as a title. Sort of like Lord, Barron, or Bishop)
You also remember these stories mentioning that he liked to leave caches in locations he visited often. Books, scrolls, ect... Items he might need but didn't want to carry with him.
Lydia - The aura seems has a strong tone of preservation and protection. As an educated guess, you'd say the stone and what ever is under it was enchanted to protect it from the elements.
(ooc: think magical tuperware)