It preserves fossils dating back to the middle to upper Miocene epoch of the Neogene period, most of which were deposited in a deepwater environment.

[2] Owing to its depositional environment, it is one of the very few geologic formations to preserve articulated specimens of fossilized deep-sea anglerfish.

[1] The Yorba Member of the Puente Formation preserves some of the world's only known fossils of deep-sea anglerfish, most of which were discovered during the construction of a rail line.

These anglerfish are assigned to several genera and species that inhabit hypoxic, upwelling-influenced subtropical and tropical environments in the eastern Pacific today, suggesting that the composition of these ecological communities has changed little in the time since the deposition of this formation.

These taxa are not found off the coast of California today, suggesting that the region was much warmer and more tropical during the late Miocene.