The 5,000-ft-thick Gannett Group, confined to the thrust belt of southeastern Idaho, western Wyoming and northeastern Utah, overlies the marine Jurassic Stump Sandstone and is overlain by the Cretaceous marine lower Tygee Member of the Bear River Formation. In ascending order, the 5-unit Gannett consists of the Ephraim Conglomerate, Peterson Limestone, Bechler Formation, Draney Limestone, and a mudstone unit herein designated the Smoot Formation. Except for the lower part of the Ephraim, which contains Late Jurassic marine mollusca, all units of the Gannett contain charophytes and fresh-water ostracods of Aptian to Albian age.

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