Quaternary Terraces of Colorado below its emergence from the plateau and canon area (4); la Quaternary littoral 
deposits ; 2, Marine Tertiary; 3, Upper Cretaceous of undulating Black Prairie area; 4, Lower Cretaceous of “Hard 
Lime Rock,” “Mountain” or plateau area; 5, Carboniferous shales and limestones; 6, Silurian; 7a Potsdam; 7b, 
Llano ; 8, Granite. Basalt at Pilot Knob. 
