| The Shiyanhe Formation exposed at the Sigang section,Neixiang area,Henan Province,central China have been investigated of conodonts.The collected 33 samples yielded 8858 conodont specimens.The conodonts are referred to 15 genera and 34 species,but four species cannot be positively identified and one taxon is kept in open nomenclature.The new Oulodus ulrichi,the Oulodus robustus,the Aphelognathus grandis and the Aphelognathus divergens conodont biozones are introduced and the conodont fauna and zones of the Shiyanhe Formation are referred to the Katian Stage(Stage slices Ka2-Ka4)of the Upper Ordovician.The presence of biostratigraphical important species of the genera Aphelognathus,Oulodus and Yaoxianognathus allows for the recognition of the previously defined local conodont biozones and that have been established from the studied section.Regionally the Shiyanhe Formation fauna is relatively similar to the contemporaneous faunas from the Tarim terrane in western China and from the southwestern margin of the North China Platform.However,the fauna composition also shows a close affinity to the North American Midcontinent Province and correlation to North American is clear.The conodont fauna in Studied Area is dominated by the species of Aphelognathus grandis,Aphelognathus divergens,Aphelognathus grandis,Aphelognathus grandis,Aphelognathus grandis,Belodina confluens,Belodina stonei,Drepanoistodus suberectus,Oulodus robustus,Oulodus ulrichi,Panderodus gracilis,Phragmodus undatus,“Plectodina” tenuis,Yaoxianognathus yaoxianensis,and the Aphelognathus—Oulodus biofacies,The “Plectodina” biofacies,the Panderodus biofacies,the Drepanoistodus biofacies and the Phragmodus biofacies have been established using multivariate statistical techniques on the conodont assemblage.The turnover of the conodont biofacies is related to sea-level changes and the biofacies are used to demonstrate the transgressive–regressive pattern in studied section. |
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