Hi Kaia,

Do you have any pictures? There are lots of naturally occurring petroleum deposits across the state, but as oil is lighter than water they are pretty easy to identify as they have an oily sheen to them. Sounds like either an algae occurring, or one of the other types of mineral springs found in the state. Sulfur springs are the most common, and usually have an orange or green tinge to them. I'm sorry I can't be too specific as to what it was, but I'm pretty sure it's not a tar pit for the reason above.