| details |
Middle Cenomanian |
|
Iowa |
Ravn,R.L. et al. The Mid-Cretacous boundary in the western interior seaway, central United States: Implications of palynostratigraphy from the type Dakota Formation. (In: Perspectives on the eastern Margin of the Cretaceous Western Interior Basin. G.W. Shurr et al, editors) |
1994 |
| details |
Early Cenomanian |
|
Iowa |
Ravn,R.L. et al. The palynostratigraphy of the Dakota Formation, (?Late Albian-Cenomanian) in its type area, northwestern Iowa and northeastern Nebraska, USA. |
1995 |
| details |
Cenomanian |
|
Minnesota |
Srivastava,S.K. Microspores from the Fredericksburgh Group (Albian) of the southern United States. |
1975 |