3Ic(it< and Call — Zeiss of Des Moln>-s, hm-a. 



abandoned channel of that river. From 

 western border rise two insulated plater 

 of characteristic loss topography but w 



ard by the erosu 



valley. 



rth of the Des Moines 



he most elevated pla- >| 

 wo-thirds of its height | - Q§ 



their summits; the southernmost, known 

 as "Capitol Hill," being the higher. Both 

 have nuclei of Carboniferous rocks forming 

 perhaps three- fourths of their altitudes; 

 and both arc manifestly separated from the 

 high land to "' 

 the Des Moil 

 West and 

 Raccoon rivers liei 

 tcau of this region , 

 being formed of Carboi 

 deeply scolloped on all sides by steep-sided 

 labyrinthine ravines such as cl 

 loss areas: hut interiorly it undulates gently 

 in qmujiiaveixil slopes forming mounds and 

 basins manifestly not due to Post-quater- 

 nary erosion, while over all its higher por- 

 tions numerous erratic bowlders, sometimes 

 smoothed and striated, lie on or near the 

 surface. Northwestward the surface de- 

 fines gently, and the plateau merges into 



rorn the ge 



itlv 



, dnla 



in-- 



1 rift plain be- 



ond. Over 



this 









ast of Four 



\li! 



creek 



the 



drift is some- 



?hat modified s 



ipertiei 



illv. 



Still farther 



westward ris 



es a 



-mallei 



ins 



j la ted plateau 



of l«".ss-liki 







; "va ma;.! . . is. all ex- 



tending N.N.W. from the Eaccoon valley 

 in a series of lobes each of which resembles 

 somewhat the ridge east of Des Moines. 



South of the two rivers and east of the 

 westernmost Four Mile creek, the topo- 

 gniphical configuration and the superficial 

 deposits are the same, in the immediate 



tral 



iteau above the confluence of the 

 rivers; the Carboniferous strata forming 

 perhaps three-fourths of the height of the 

 bluffs. The altitude here is rather less 





