Conodont zonation and correlation of upper part of Fuluoian of Lower Ordovician in Huanghuachang section,Yichang, Hubei

Abstract：Based on a systematic study of the conodont biostratigraphic data in the former Oepikodus evae zone of the Fuluoian in the Huanghuachang section, the authors discussed several problems concerning the apparatus classification of some important multi-element conodonts: Stolodus stola, L. gladiatus, O. intermedius, Oepikodus communis, Prioniodus honghuayuanensis. The upper part of the former Oepikodus evae zone, without the zonal index fossil Oepikodus evae itself in the Huanghuachang section, conflicts with the definition of interval zone and range zone in International Stratigraphic Guide (2000). Through further collecting conodont samples, checking and revising some of the conodont general and species in the former O. evae zone, the authors analyzed the vertical conodont distribution. The interval from the base of Honghuayuan Formation to the top of Lower Member of Dawan Formation was divided to 4 interval zones: Prioniodus honghuayuanensis zone, O. evae zone, Trapezognathus diprion zone and Baltoniodus cf. B. triangularis zone, and 3 subzones: Stolodus stola subzone, Oepikodus intermedius subzone and Microzarkodina sp.A, in upward succession. The Prioniodus honghuayuanensis zone, Trapezognathus diprion zone and Baltoniodus cf. B. triangularis zone are new zones, and the Oepikodus intermedius subzone and Microzarkodina sp.A are new subzones in this paper. The former Stolodus stola subzone is revised herein. Abundant warm-water fauna conodonts, including Reutterodus andinus，Oepikodus intermedius, Juanognathus variabilis, were found in Trapezognathus diprion zone -Baltoniodus cf. B. triangularis zone in the Huanghuachang section; consequently, these two zones could be serving as a standard for the stratigraphic division and correlation of the relevant strata in central continent of North America. Furthermore, the above bio-stratigraphic division scheme can supply reasonable advice for the precise stratigraphic division and correlation for different biogeographical zones among different continents around the world.