Discovery of Ordovician acritarchs in Buqingshan ophiolite complex, East Kunlun Mountains and its significance

This note reports the first discovery of Middle-late Ordovician acritarchs from the Buqingshan ophiolite complex of the southern ophiolite zone of Eas t Kunlun, The acritarch assemblage is dominated with acanthomorphids (appro x, 32%) and sphaeromorphds (approx. 63%) and contains more characteristic f orms, such as Lophosphaeridium edenense, L. varum, Nothooidium sp,,? Buedin giisphaaeridinm sp,, Virbysphaera sp., Strophomorpha sp., etc. In addition, some tube-like fragments and tetrads, which are recognized as affinity to terrestrial plants and usual occurrence in Late Ordovician-Early Silurian s trata, are preserved together with acritarchs. All the known fossil evidenc e indicates that the strata should be Middle-Late Ordovician in age. It not only provides paleontological proof for the existence of Ordovician ophiol ite, but also challenges the usual ideas on strata composition of the studi ed area and the southern ophiolite zone of East Kunlun, and the models on t ectonic framework and evolution of this area and the northern part of the Q inghai-Tibetan Plateau.