Measured By Condra and Upp, 1931; Schroyer Limestone,Limestone, upper 2 ft. gray, massive, non-cherty; middle portion, cherty; base shaly; combined thickness,Shale and limy material,Limestone, dark gray, badly weathered,Havensville Shale,Shale, gray,Limestone, shaly,Shale, bluish-gray,Limestone, gray, earthy,Shale, gray,Shale, bright olive, argillaceous,Fourmile Limestone,