Changhsingian

Changhsingian is the uppermost stage of the Permian period, the last stage of the Paleozoic era. It forms the final part of the Lopingian epoch and is named after a locality in China (Changhsing/Changxing) where rocks of this age are well represented. The stage spans roughly from about 254 million years ago to around 251.9 million years ago, ending with the Permian–Triassic extinction event that inaugurates the Triassic.

Stratigraphically, the Changhsingian is recognized worldwide in marine sedimentary records. Its base and top are defined within the framework of the International Chronostratigraphic Chart, with the upper boundary marking the Permian–Triassic boundary. The interval is often studied through biostratigraphy, using fossils such as conodonts and ammonoids, as well as chemostratigraphic signals, to correlate sections across continents.

Fossil assemblages from the Changhsingian show a dramatic turnover compared with earlier Permian stages. Marine faunas decline in diversity, and many groups, including fusulinids and certain ammonoids, exhibit major reductions in abundance. This stage sits within the broader context of the late Permian climate crisis, characterized by global warming, widespread ocean stratification and anoxia, and large-scale volcanism associated with the Siberian Traps. The end of the Changhsingian aligns with the most extensive mass extinction in Earth history, eliminating a large fraction of marine and terrestrial species and paving the way for the Early Triassic recovery.