re: It is strange, though
"No apparent local volcanos to make the ash."
Sure, besides Olympus Mons, Pavonis Mons, Arsia Mons, Ascraeus Mons, Elysium Mons, Syrtis and all the other volcanos on Mars. It doesn't necessarily have to be made locally. I remember Mt St. Hellens dumping ash on Montana (~1500km away) and further states. Who knows what was going on when this formation was deposited, assuming it IS ash. I don't think the fine powdery surroundings have to be ash. I'll wait for the official word though.