Exploration-scale cross sections of the Mississippian Madison Formation of Wyoming and Montana show variations in the distribution of dolomite and porous dolomite in a sequence-stratigraphic hierarchy along a 500-km dip transect. These variations in the distribution of dolomite across the ramp have significant implications for exploration and dolomitization models. This study also shows how understanding of rock and porosity types and vertical and lateral reservoir distribution and compartmentalization can be better understood through outcrop studies.