"From 280 to 310 million years ago" . . . . . "Conodont distribution, paleoecology, and preliminary biostratigraphy of the Upper Cherokee and Marmaton groups (Upper Desmoinesian, Middle Pennsylvanian) from two cores in south-central Iowa"@en . . . . . . . . . . . . . . "Conodont distribution, paleoecology, and preliminary biostratigraphy of the upper Cherokee and Marmaton groups (upper Desmoinesian, middle Pennsylvanian) from two cores in south central Iowa"@en . . . .