RE-DEFINITION OF THE ST. LOUIS-STE. GENEVIEVE BOUNDARY IN SOUTHEASTERN IOWA

Previous work has suggested that the "St. Louis" Formation in Iowa, as it has been known for much of the past century, cannot be fully correlated with the type sections on the Mississippi River. More recent studies have used sequence stratigraphy and sea-level curves in addition to new biostratigraphic information. This work demonstrates that the basal Croton and Yenruogis Members are St. Louis-equivalent; whereas the overlying Verdi and Waugh Members can be tied to the Ste. Genevieve Formation as recently defined.

The Waugh Member of the Ste. Genevieve Formation is of paleontological importance because of the early tetrapod site near Delta, Iowa. This site can now be dated to approximately 330 million years ago, Late Viséan/lowermost Chesterian, Late-Middle Mississippian Period.