"Clermont Shale Member" "Clore Formation" "Coffeen Limestone Member" "Coggan Member" "Cohn Coal Member" "Colchester Coal Member" "Conant Limestone Member" "Cooper Limestone Member" "Copperas Creek Sandstone Member" "Cora Limestone Member" "Coralville Member" "County Line (Alburnett) silt" "Covel Conglomerate Bed" "Coxville Sandstone Member" "Cramer Limestone Member" "Crane Member" "Creal Springs Limestone Member" "Cretaceous System" "Croixan Series" "Crowleys Ridge Silt"