DinoDigHell Creek Formation
Late Cretaceous (Maastrichtian) terrestrial unit of the Western Interior, famous for Tyrannosaurus and Triceratops.
Late Cretaceous · 100.5–66 Mya
Period
Late Cretaceous
Country
United States
About
The Hell Creek Formation crops out across Montana, North and South Dakota, and Wyoming, recording the final two million years of the Cretaceous before the K–Pg extinction. Its mudstones and channel sandstones preserve one of the most intensively sampled terrestrial vertebrate faunas on Earth.
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Map of known sites
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