The Wahweap Formation is a Late Cretaceous rock unit in southern Utah and northern Arizona around Lake Powell within Grand Staircase–Escalante National Monument. Dating to the Campanian and divided into four members, it preserves a long span of time that helps trace environmental and faunal change in the region. Its rich fossil record includes dinosaur remains, mammals, invertebrates, and trace fossils. Discoveries range from shell beds, fossil crabs, insect burrows, and more than 1,900 gastropods to tracks of crocodylomorphs and dinosaurs. A notable 2010 find appears to capture a predator-prey interaction at mammal dens, making the formation valuable for evidence of behavior as well as bones.