Conodonts From The Denominated Section Of Carboniferous Benxi Formation, Benxi, Liaoning

The stratigraphical section in Niumaoling of Benxi, Liaoning is the denominated profile of Carboniferous Benxi Formation, and was named by Zhao Yazeng (Chao DY) in 1926 and are well-known in the world. The section demonstrates a distinct and continuous sequence of the Upper Carboniferous and much fossiliferous in animals and plants, and characteristic for the biostratigraphic correlation regionally. However, the study of conodonts fossils in this section has not been done thoroughly during the past years.This paper reports the new advance on the study of conodonts from the upper Benxi Formation in this denominated profile in the Niumaoling. These are 11 genera and 29 species of conodonts are described here. The author found the index fossils of the middle Moscovian Idiognathodus podolskensis and middle-upper Moscovian Neognathodus roundyi for the first time, and proposed Idiognathodus delicates--I. podolskensis Zone representing the conodonts assemblage in the upper Benxi Formation of this section. Based on the discovery of some index Late Carboniferous Moscovian fossils, e.g. Idiognathodus podolskensis, I. delicatus, Neognathodus roundyi, N. inaequlis, the upper part of the Benxi Formation can approximately be correlated with the middle-upper Moscovian Stage of the International Stratigraphic Chart or the middle Desmoinesian of North America. Since Idiognathodus sagittalis and Swadelina, indicating the late Pennsylvanian in age, have not been found yet, the upper part of the Benxi Formation in this section have not achieved Kasimovian in age. The new research advance provides a more detailed evidence for confirming the geological age of the Benxi Formation.As there are some thick strata in the lower part of Benxi Formation in this section, which yielding a lot of fossil plabts represented by Sublepidodendron—Archaecalamites assemblage, and based on the stratigraphic correlation with those of the adjacent areas of the Niumaoling, the author considers that the lower Benxi Formation probably includes the deposits of the upper Lower Carboniferous.