PLATE 13 

 Tectonic Map of the Cretaceous-Tertiary Transition 



Thickness of latest Cretaceous and Early Tertiary deposits in Rocky Mountain 

 basins not shown. For detail see Figs. 22.4, 22.5, and 22.6. The crypto- 

 volcanic structure in Iowa is Late Cretaceous or Early Tertiary; the others are 

 not dated but are presumed to be of the same age. 





