undifferentiated rock units

Paleontology and geology

Permian deposits (shown as undifferentiated on this map) include volcanic rocks in the west-central part of the state and marine deposits in the eastern portions. The Phosphoria Formation of eastern Idaho is mined for its rich phosphate deposits and contains fossils of spiral-toothed sharks, cartilaginous and bony fishes, corals, brachiopods, gastropods, bryozoa, cephalopods, pelecypods, and ostracods.