Paleontology and geology
During the Carboniferous, part of what is now Oregon was a tropical oceanic island. Early Carboniferous limestones in one small area of central Oregon have yielded corals, large brachiopods, and other fossils typical of animals that live on tropical coral reefs. Nearby is a fossil plant locality dating to the early part of the Late Carboniferous. These plants are quite different from those of equivalent age in the mid-continental region, probably because of their island isolation.