Early Carboniferous radiolarians from north‐west Thailand: palaeogeographical implications

Moderately well‐preserved radiolarian assemblages are described from bedded cherts south of Mae Hong Son, north‐west Thailand. Twenty species and subspecies are identified, including one new species (Archocyrtium sashidai Feng sp. nov.). The assemblages belong to the middle Early Carboniferous Albaillella indensis and Eostylodictya rota zones. The new data suggest that there was a pelagic basin between the Shan‐Thai terrane and Gondwana during the Early Carboniferous. This implies, contrary to previous interpretations, that the Shan‐Thai terrane had already rifted apart from Gondwana during the Early Carboniferous.