First of three epochs of the Triassic Period
Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.902 Ma and 247.2 Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a unit in chronostratigraphy.
The Early Triassic is the oldest epoch of the
Mesozoic Era. It is preceded by the Lopingian Epoch (late Permian, Paleozoic Era) and followed by the Middle Triassic Epoch. The Early Triassic is divided into the Induan and Olenekian ages. The Induan is subdivided into the Griesbachian and Dienerian subages and the Olenekian is subdivided into the Smithian and Spathian subages.
The Lower Triassic series is coeval with the
Scythian Stage, which is today not included in the official timescales but can be found in older literature. In Europe, most of the Lower Triassic is composed of Buntsandstein, a lithostratigraphic unit of continental red beds.
The Early Triassic and partly also the
Middle Triassic span the interval of biotic recovery from the Permian-Triassic extinction event, the most severe mass extinction event in Earth's history.   A second extinction event, the  Smithian-Spathian boundary event, occurred during the Olenekian. A third extinction event occurred at the Olenekian-Anisian boundary, marking the end of the Early Triassic epoch. 
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