Large quantities of limestone are deposited. Mississippian-age reservoir rocks hold an abundant amount of oil and gas. Devonian 410 Shallow, temporary seas in eastern Utah, and deeper seas in the west contain primitive fish, corals, brachiopods, and conodonts. The Stansbury uplift in north-central Utah develops into a prominent ridge above sea level during the Late Devonian. Silurian 435 Shallow seas containing corals and brachiopods blanket Utah.
Dolomite is the predominant rock being formed.
Ordovician 500 New life forms prosper in fluctuating seas of western Utah while eastern Utah remains above sea level. The first vertebrates, primitive armored fish, evolve. Cambrian 570 Subsidence of western Utah continues. Trilobites thrive in the deep seas of western Utah, while shallow, oscillating seas cover eastern Utah. Granitic and metamorphic rocks found south of Salt Lake City are material that collided and adhered to the south side of the continent between 1.6 and 1.8 billion years ago.