I've seen that on my paint before. I almost crapped, got the detailer, and it wiped off. I think it was some kind of insect or plant funk. It didnt wipe right off, I had to work at it but it didn't leave an indentation or stain or any thing.
'09 Pacific Slate G8 GT "stock" 1900 Magnacharger, 441 rwtq, 441 rwhp. Rotofab intake, Kooks 1 7/8" lt's,cats, midpipe, SLP Loud Mouth exhaust. Pedders lowered touring package. Baer Pro front brakes, Forge Star F14 GunMetal 19x8.5, Michelin Pilot Sport a/s tire's. '78 ElCamino. 2008 model Blue Heeler.