Chinle Formation

The Chinle Formation is a Late Triassic sequence of sedimentary rocks exposed across the southwestern United States. Its river, lake, and floodplain deposits preserve abundant fossils, including early dinosaurs and other vertebrates.

Late Triassic: The final epoch of the Triassic Period, spanning about 237 to 201 million years ago. The Chinle Formation accumulated during this interval.
Sediment transport: The movement of sediment by water, wind, ice, or gravity. Rivers carried the grains that built Chinle channel and floodplain deposits.
Petrified Forest National Park: A national park in Arizona known for colorful Triassic strata and fossilized wood. Its Painted Desert exposures are among the best-known Chinle outcrops.
Moenkopi Formation: A Permian–Triassic sedimentary rock unit exposed across parts of the southwestern United States. It commonly underlies Chinle strata and records older regional landscapes.
Radioisotopic dating: A method of estimating a material's age from the decay of radioactive isotopes. Radiometric dates constrain the timing of Chinle deposition and fossil assemblages.
Stratigraphy: The study and description of layered rocks and their relationships through time. The formation is a stratigraphic unit whose layers preserve changing environments.
Stratigraphic formation: A mappable body of rock defined by distinctive lithology and stratigraphic position. The Chinle is classified as a formation within regional rock successions.
Ghost Ranch: A fossil-rich site in New Mexico that preserves Late Triassic animals. Its Chinle deposits yielded important early dinosaur and reptile fossils.
Dockum Group: A Late Triassic rock succession exposed across the southern High Plains of the United States. Its age and depositional record overlap with the Chinle farther east.
Magnetostratigraphy: The use of preserved magnetic polarity patterns to correlate and date rock sequences. Magnetic reversals help correlate Chinle strata where direct dates are sparse.

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