foraminifera in the upper Blue Gate, Clioscaphites vermiformis and Clioscaphites choteauenis, was used to date this member. An ancient shoreline once again approached the area, resulting in the formation of the locally 300 to 400 feet (90 to 120 m) thick Muley Canyon Member. It is composed of evenly bedded, fine-grained sandstone and carbon-rich shales. Coal beds are found in the upper parts of this member, indicating continental coastal plain conditions at that time. Alternating layers of shallow marine and non-marine sediments were deposited as the shoreline fluctuated back and forth over the area. These sediments became the locally 650 to 750 foot (200 to 230 m) thick Masuk Member. The Masuk consists of cliff-forming cross-bedded sandstones and slope-forming yellowish-gray to bluish-gray mudstones with interbedded light gray sandstones. Fossils of bivalves, ceratopsian dinosaurs, crocodiles, gastropods, and turtles have been collected in this member. The Western Interior Seaway was shrinking due to infilling and uplift while the high mountains to the east were being reduced by erosion. Barrier beaches and river deltas migrated eastward into the seaway. The resulting 300 to 400 foot (90 to 120 m) thick Mesaverde Formation consists of light-brown to dark-gray thick-bedded and cross-stratified sandstone with interbedded dark gray shale and intertongues with the Masuk Member of the overlying Mancos Shale. Only small remnants are found capping a few mesas in the park's eastern section. Uplift and Cenozoic events Waterpocket Fold, Lake Uinta and volcanism The Laramide orogeny compacted the region from about 70 million to 50 million years ago and in the process created the Rocky Mountains. Many monoclines (a type of gentle upward fold in rock strata) were also formed by the deep compressive forces of the Laramide. One of those monoclines, called the Waterpocket Fold, is the major geographic feature of the park. The 100 mile (160 km) long fold has a north–south alignment with a steeply east-dipping side. The rock layers on the west side of the Waterpocket Fold have been lifted more than 7,000 feet (2,100 m) higher than the layers on the east. Thus older rocks are exposed on the western part of the fold and younger rocks on the eastern part. This particular fold may have been created due to movement along a fault in the Precambrian basement rocks hidden well below any exposed formations. Small earthquakes centered below the fold in 1979 may be from such a fault. Contemporary