Early Deposits and Events
The broad inland basins that were formed late in the Cretaceous Period received sand, silt, and mud brought in by streams from the uplifted or folded areas. These materials became compacted into the Wasatch Formation—the red or pink rock from which Bryce Canyon National Park was sculptured. One such basin lay just northeast of the Monument. The Monument probably was covered by some of these stream deposits after the main basin was partly filled.
The mammals that roamed the area during the Paleocene Epoch were primitive, but more advanced forms appeared later, in Eocene time. Some of their fossil remains have been found in the Wasatch Formation in Plateau Creek Valley north of Grand Mesa and near Rifle, about 60 miles northeast of Grand Junction. The entire 5,000 feet of the Wasatch may be seen along U.S. Highway I-70 between the towns of DeBeque and Grand Valley, and much of it helps support towering Grand and Battlement Mesas.