Biostratigraphical and palaeogeographical significance of Late Ordovician acritarchs from Dawangou, Xinjiang

A well-preserved and diverse acritarch assemblage was recovered from four Upper Ordovician formations of the Dawangou section, Xinjiang, northwestern China (Tarim Block). This palynomorph assemblage consists of 27 species assigned to 17 genera. The palynomorph assemblage is dominated by acanthomorphic acritarchs (particularly species of Baltisphaeridium), followed by netromorphs, represented by Navifusa. Comparison of the palynomorph assemblage with correlative age assemblages elsewhere supports the observation that there was little faunal or floral provincialism during the Late Ordovician. In addition, 13 species recovered from the Dawangou section are restricted to the Caradoc—Ashgill, and have a wide geographical range making them useful biostratigraphical taxa.