1. Structure contour maps on the base of Mississippian strata and the top of upper Cambrian strata, Springfield 1⁰?x 2⁰ quadrangle, Missouri Yale Public content 1989. 2002-06-01T04:00:00Z. 2004-04-05T13:41:13Z. Geological Survey (U.S.). The Survey ; a Denver, CO : For sale by Map Distribution. English. Public. Missouri. Mississippian and Cambrian.