Abstract

Almost 13,000 feet of Mesozoic marine, continental, and transitional rocks are exposed in and around the Duchesne River area, northeast Utah. They consist of at least 16 mappable rock units. Cretaceous deposits aggregate 6,000 ft. They are dominantly marine, but include sequences of continental beds, especially reworked stream channel deposits, and deltaic, lagoonal and swamp deposits formed along the Cretaceous coastline. Only the Currant Creek Formation of Late Cretaceous-Paleocene age is dominantly nonmarine. Jurassic deposits are about 4,500 ft thick. About four-fifths of the sequence are continental beds that include the eolian parts of the Nugget and Entrada sandstones and the fluvial Morrison Formation. Triassic deposits, which are 2,400 ft thick, are dominantly paralic and nearshore marine sequences. About one-fifth of the beds are fluvial, saline lake, and low-gradient stream deposits. These continental deposits are represented by the Gartra and Popo Agie formations.