Oily wall

Hi, I've noticed a strange thing in my 69 Dart that I would like some help on if possible. I've noticed that after a drive when I return home and pop the hood, there is a spray of oil on the wall next to the alternator. I wipe it up and the next few times I drive it, the oil spray is there again. Could anyone tell me where the oil is coming from and what causes it?

thanks,
Joel