Induan

Induan is the earliest age or stage of the Triassic Period, the first stage of the Lower Triassic. It directly follows the Permian–Triassic extinction event and precedes the Olenekian. The Induan spans roughly from 251.9 to about 249.7 million years ago, a span of about 2 to 3 million years depending on dating conventions.

Stratigraphically, the base of the Induan is defined by the global appearance of the conodont Hindeodus parvus at the Permian–Triassic boundary, marking the start of the Triassic. The upper boundary marks the transition to the Olenekian. The stage is studied worldwide in marine and continental deposits that record the immediate post-extinction interval and the initial beginnings of Triassic recovery.

Paleogeography and climate during the Induan were dominated by the supercontinent Pangaea and a hot, greenhouse climate with high CO2 levels. Ocean environments experienced instability and widespread depletion of biodiversity, with evidence of short-lived anoxic events and disrupted ecosystems. Terrestrial systems were in a prolonged early recovery phase, with plant and vertebrate communities gradually regrowing from a limited set of survivors.

Biota and recovery: The Induan is characterized by low overall biodiversity and ecological complexity as life reestablished itself after the mass extinction. In marine realms, conodonts, bivalves, and other r-selected groups reappeared, while ammonoids and reef builders began to reoccupy niches. By the Olenekian, diversification and ecosystem complexity increased more noticeably, marking a more robust recovery.

Significance: The Induan represents the opening chapter of the Triassic recovery, setting the stage for later radiations that would diversify Triassic ecosystems.