220 
IOWA ACADEMY OF SCIENCE 
Figure 6. — Edge of the high gravel plateau between the reversed portion of 
the Little Maquoketa valley and the Mississippi river. 
Figure 7. — Map showing the parallelism and vertical walls of the gorge of 
the Mississippi river, the reversed portion of the Little Maquoketa valley, and 
the abandoned channel between Sageville and Dubuque. 
