Late Jurassic to early Cretaceous radiolarian faunas from Changku, Gyangze, southern Tibet: Implications for the evolution of the Neo-Tethys

Abstract

Radiolarians found in siliceous sediments within the Yarlung-Tsangpo Suture Zone in southern Tibet contain valuable geochronological and tectonic information for the evolution of the Neo-Tethys. Radiolarians, as the main microfossils contained in radiolarian cherts, are commonly used to determine the age of the chert. The study of radiolarian biostratigraphy is crucial in interpreting the tectonic nature of associated oceanic terranes, which can aid in restoring the evolution of the Neo-Tethys. A large number of poorly to well-preserved radiolarian fossils were recovered from a chert block near Changku, Gyangze, in southern Tibet. A total of 57 species attributed to 36 genera have been identified from eight productive samples. Four radiolarian assemblages have been identified by comparison with established radiolarian zones of the Neo-Tethyan realm and have been precisely dated to the late Kimmeridgian to earliest Hauterivian. The origin of the exotic blocks in the Zongzhuo Formation has been subject to different interpretations, and the chert block near Changku should be of tectonic origin.