The Thæ Chu formation was established in 2001 for describing the red beds occurring in the Thæ Chu Archipelago, Kiªn Giang Province. It has been dated as Cretaceous on the basis of palynological materials and silicified wood.

Recently the palynological materials were recollected and systematically studied that has been leading to the finding of Coniopteris. Together with Cicatricosisporites, Brachyphyllum and Classopollis, they form a characteristic assemblage allowing to date more precisely the Thæ Chu Formation as Early Cretaceous.