According to radiometric dating, the Morrison Formation dates from 156.3 ± 2 million years old (Ma) at its base,[3] to 146.8 ± 1 million years old at the top,[4] which places it in the earliest Kimmeridgian, and early Tithonian stages of the late Jurassic. This is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania.