Cambrian brachiopods from the area of the former Semipalatinsk nuclear-testing site, Chingiz Ranges, Kazakhstan

The first Cambrian (Miaolingian to Furongian) rhynchonelliform brachiopods are described from the Chingiz-Tarbagatai early Palaeozoic island arc system in eastern Central Kazakhstan. The Miaolingian (Wuliuan) assemblage from the volcano-sedimentary Athei Formation includes the kutorginide Bellistrophia askarensis sp. nov. Popov and Nikitina, protorthide Psiloria karasuensis sp. nov. Popov and Nikitina, chileide Matutella sp. and an unidentified naukatide, which occur together with the acrotheloid Schizopholis sp. A single specimen of Bellistrophia exhibit an incompletely preserved fossilised Nisusia-type pedicle. The co-occurrence of Psiloria and Schizopholis indicates a clear Gondwanan affinity of the fauna. The Furongian Irisai Formation contains extensive brachiopod shell beds formed by poorly preserved, disarticulated valves of Billingsella sp. Stilpnotreta magna is for the first time documented from Chingiz Ranges, where it occurs in the Ordotas Formation. The Cambrian stratigraphy of the former Semipalatinsk nuclear-testing site is reviewed, and the Irisai Formation is formalised.

Automated summary

The study describes the first Cambrian rhynchonelliform brachiopods from the early Palaeozoic island arc system in eastern Central Kazakhstan, including new species from the Athei Formation and Irisai Formation. The co-occurrence of Psiloria and Schizopholis indicates a clear Gondwanan affinity of the fauna in the region. The Cambrian stratigraphy of the former Semipalatinsk nuclear-testing site is reviewed, and the Irisai Formation is formally named.