"Bituminous rocks of Mississippian age crop out in northwest Alabama along a 70 mile long belt that extends from central Morgan County westward to n ear the Alabama-Mississippi boundary. Bitumen deposits have been confirmed by core-holes to be present in the subsurface for a distance of at least 10 to 15 miles south of the outcrop. Due to the lack of well control, the actual downdip limit of the deposits cannot be determined. Saturations and thickness of the bitumen deposits vary widely throughout northwest Alabama. The highest measured saturations approach 10 percent by weight and exceed 60 percent of the pore space. Measured thickness in the outcrop range up to almost 20 feet; however, core-holes have encountered bitumen deposits up to 30 feet thick and multiple-impregnated zones are common. Estimates of the total reserves for the Hartselle Sandstone in both the outcrop and subsurface areas range up to 4.2 billion barrels, but future test-drilling to define the downdip limits could result in this estimate being increased to more than 5 billion barrels."