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Which geologic stages make up the Early Jurassic Epoch?
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Jurassic Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Jurassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The Early Jurassic Epoch is composed of four distinct geologic stages. In chronological order, these are:
- Hettangian Stage: The earliest stage, occurring between 201.3 million and 199.3 million years ago.12
- Sinemurian Stage: The second stage, spanning from 199.3 million to 190.8 million years ago.31
- Pliensbachian Stage: The third stage, occurring between 190.8 million and 182.7 million years ago.41
- Toarcian Stage: The final stage of the Early Jurassic, spanning from 182.7 million to 174.1 million years ago.15
These stages are defined primarily by the use of index fossils, such as ammonites, which help geologists correlate rock strata worldwide.1