CONODONT DISTRIBUTION DATA IN SEQUENCE STRATIGRAPHIC DEFINITION AND WATER MASS CHARACTERIZATION: EXAMPLES FOR THE CARBONIFEROUS OF NORTH AMERICA

In the Gzhelian to Sakmarian deposits of Kansas, maximum abundance and diversity of conodonts occurs within fossiliferous gray shales that also exhibit the highest diversity of marine macroinvertebrates and clearly indicate maximum flooding. Peaks in abundance and diversity through an individual cycle indicate multiple flooding surfaces. The faunas are dominated by Streptognathodus species. A single Moscovian cyclothem, the Lower Kitanning Cycle, was analyzed across the North American Continent. The abundance and diversity of conodonts indicate two flooding events through this cycle, that is, two fifth order cycles within the fourth order cyclothem. Maximum species diversity indicates the maximum flooding surface. This surface does not occur within black shales of the classic MidContinent cyclothem but within the shale/limestone transition. The cycle in the parts of the West, and specifically Nevada, is represented by carbonate deposition with common chert replacing evaporite minerals indicating normal marine to hypersaline conditions. The conodont faunas are dominated by Neognathodus and (or) Adetognathus. Organic black carbonate mudstones and shale deposition indicates high nutrient waters and high productivity. When faunas are present, they are dominated by Gondolella species. Fossiliferous gray shale and limestone generally indicates deposition in normal marine conditions and these deposits are dominated by Idiognathodus species. Sedimentological evidence suggests deposition with more and more fresh water influence in the East and there is a subtle change in the conodont faunas from multiple species of Idiognathodus in Illinois and Indiana that reduce to a single species in Ohio and Pennsylvania and there is a change in Neognathodus species. It appears that Neognathodus is sensitive to salinity of the waters so that the species that is common in the normal marine to hypersaline waters in Nevada is only a small part of the faunas of the MidContinent, and absent from Ohio. Conversely, the species that is present in normal marine to hyposaline waters in Ohio is absent from Nevada.