You really gonna try to oh sure away the La Brea tar pits. Woolly mammoths, dire wolves, giant sloths, saber toothed cats along with rodents, birds, and reptiles got a little more than tar on their feet. Been seeping for a long time.

San Diego does not get effects of continual seepage, Monterey formation (where the oil is) goes offshore around south Newport Beach. Seepage more prevalent in Los Angeles and Ventura counties. Of course was worse during spill, but historical records of seepage in La Harbor exist and it continues to this day.