In western Utah sands 2500' thick. B. Marine Sedimentation Dominance of the Late Jurassic interior seaway called the Sundance Sea which extended from the Arctic to almost the Gulf of Mexico. Named after the Sundance Fm of the Black Hills, S. Dakota. Sundance Sea became restricted northward near the end of the period filling with clay, silt, and sandstone. Formed in region of Sundance Sea following its regression.
Cycads are the dominant plants and conifers also common.
Flowering plants still rare. Ammonites very common. Dinosaurs at peak abundance with hundreds of species. The largest dinos occurred near the end of the period. Several types of primitive mammals present but not common.