Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 195 



GEOLOGY AND SOILS 



The sandhills are underlaid by a series of geological formations 

 which are probably continuous (Darton 33, Barbour 2, Condra 28) 

 beneath the entire state. The oldest geological formation exposed 

 in Nebraska is the Pennsylvanian (Carboniferous). This series, 

 composed of limestones and shales, is of great thickness and it fur- 

 nishes products of considerable value in reference to certain indus- 



Sandhilli 



Fig. 1. Vertical section showing the bed rock. This somewhat idealized sec- 

 tion is intended to show the relation of the sandhills to the un- 

 derlying rock series. (Generalized from Barbour, Darton, etc.) 



tries of the state. Lying upon the Pennsylvanian series is a thin 

 bed of Jura-Trias. Above this bed comes in regular order a thick 

 stratum of the dark, rusty-red Dakota (Cretaceous) sandstone 

 which also yields commercially valuable grades of building stone. 

 Above this lowest sandstone there lies next in order the Graneros 

 which is mostly shale. Upon the Graneros lies a thin bed of Green- 

 horn limestone, and this in turn gives way toward the surface to an- 



