Morrison Formation, with notable fossils preserved at Dinosaur National Monument. The thickest Jurassic sediments are between Devil's Slide, east of Ogden, and Marysvale, which include gypsum and other evaporites, mined from the Arapien Shale. The Sevier orogeny to the west shed gravel and other sediments into the Morrison Formation. The formation was entirely continental in origin, recording shallow lakes, shifting streams and volcanic ash. A shallow seaway formed in the Middle Jurassic, leaving behind the fossil-bearing Carmel and Twin Creek formations. For the last time, Utah was covered by shallow seas in the Cretaceous and with the continued uplift of the Sevier orogeny leading to erosion, deposits from the time are double the thickness of Jurassic units. The Kelvin and Lower Indianola formations indicate continuous sand and gravel deposition in streams along the foothills of the mountains, while both the Burro Canyon and Cedar Mountain formations (which are rich in fossils) point to floodplain deposits similar to those in the underlying Morrison Formation. Near the Wyoming line, the Dakota Sandstone is overlain by the Aspen-Mowry Shale. In the Wasatch Plateau, the Ferron sandstone represents a brief marine regression to the east and serves as an important natural gas horizon. The Emery and Mesaverde sandstone indicate similar regressions (the Mesaverde marks the last one in the late Cretaceous). Coals formed in units such as the Straight Cliffs Formation. Cenozoic (66 million years ago-present) In the Cenozoic, the Laramide orogeny uplifted the Rocky Mountains. Near Flaming Gorge, the Paleocene Fort Union Formation angularly overlies the Cretaceous Ericson Sandstone while on the south slope of Uintas Mountain, the Wasatch Formation overlies the Cretaceous Mesaverde Sandstone. The Wasatch Conglomerate formed as the coarsest debris accumulated in basins near the uplifted areas, with sediments growing finer further east and reaching up to 13,000 feet thick through the Eocene in the Uinta Basin. Large lakes played an important role as well. Paleocene Lake Flagstaff left algal limestone in the Southern Wasatch Mountains, along with marl-mudstone in Bryce Canyon, Cedar Breaks and Richfield. Eocene Lake Green River deposits do not extend as far south, but include an important oil shale resource. Erosion wore down the Uinta Mountains enough that the Duchesne River Formation covered over earlier Cenozoic basin fill. An abrupt shift to volcanic activity in the Needle Range and at Marysvale, Crystal Peak, Tintic and Bingham took place in the Oligocene, erupt thick ash flow tuff