The bedrock of Bonneauville is red shale overlaid with a few sporadic deposits of sandstone. The sedimentary shale was formed during the Triassic Period (about 200-250 million years ago). Shale is composed of clay with iron and other trace minerals intermixed. Millions of years into the future the stone will turn to slate. There are still clay deposits around the town. In the past, some of the deposits may have been exploited for use in making stoneware pottery. (Interestingly shale, sandstone, and clay are materials that Bonneauville shares in common with the planet Mars.)

These Bonneauville fossils are elementary formations:

Sample 1985-03A is fossilized detritus of large earthworms.

Sample 1985-03B is an example of fossilized mud ripples that formed when wind caused lapping water to shape the mud at the edge of a pond or lake. The mud ripples then became overlain with more layers of mud, thus preserving them as the mass hardened.

These simple Paleontological finds were not the result of mechanized digging. They were found by laboriously removing each layer of shale from a footer ditch with a hand pick, "the old way." Found at 4A Locust St., Bonneauville, PA in 1983.