Fossils in fossil fuel
Around the same time that the ancestors of humans branched from the apes, organic sediments were being laid down that would eventually turn into oil. Some of this oil worked its way along fault lines, and began seeping out of the ground at the surface. Located in L.A. these tar pits would capture animals, preserving their bones for the descendants of those early apes to puzzle over.
Here’s a link to an article about the down side to building a city over an oil deposit that is seeping out of the earth.
Here’s a 13-minute video about the 1989 explosion, caused by methane gas from the oil deposits under the city.