Early Jurassic

The Early Jurassic is the first epoch of the Jurassic Period, lasting from about 201 to 174 million years ago. It followed the end-Triassic extinction and preceded the Middle Jurassic.

Jurassic: The Jurassic is a geological period lasting about 201 to 145 million years ago, between the Triassic and Cretaceous periods. The Early Jurassic is its first epoch.
Blue Lias: Blue Lias is a sequence of Early Jurassic limestone and shale exposed along parts of the English coast. Its layers record marine environments and abundant fossils from the epoch.
End-Triassic extinction: The end-Triassic extinction was a major loss of species around 201 million years ago, marking the boundary between the Triassic and Jurassic periods. Its aftermath opened ecological space at the start of the epoch.
Biostratigraphy: Biostratigraphy correlates and dates rock layers using their fossil content. Index fossils help divide and correlate Early Jurassic strata.
Rhaetian: The Rhaetian is the final age of the Triassic Period, immediately preceding the Jurassic. It provides the latest Triassic baseline for changes across the boundary.
Hettangian: The Hettangian is the earliest age of the Jurassic Period, lasting roughly from 201 to 199 million years ago. It begins the Early Jurassic.
Holzmaden shale: The Holzmaden shale is a Lower Jurassic marine deposit in Germany, renowned for exceptionally preserved fossils. Its ichthyosaurs, plesiosaurs, and other fossils document Early Jurassic seas.
Central Atlantic Magmatic Province: The Central Atlantic Magmatic Province is an immense region of igneous rocks formed during extensive volcanism around the Triassic–Jurassic boundary. Its eruptions are linked to environmental changes surrounding the epoch’s beginning.
Ammonite: Ammonites were extinct marine cephalopods whose coiled shells are common fossils in Mesozoic rocks. Their rapidly changing forms help date and correlate rocks from the epoch.
Middle Jurassic: The Middle Jurassic is the second epoch of the Jurassic Period, following the Early Jurassic. It marks the next interval, when ecosystems and environments continued to change.

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