The Fredericksburg Group is one of three groups of rocks which comprise the outcropping Lower Cretaceous sediments in north central Texas. Four formations form this group; from the base upward these are the Paluxy, Walnut, Comanche Peak and Edwards (fig. 1).

A thick sequence of Lower Cretaceous limestone and dolomite, known traditionally and informally as Edwards," covers much of west-central Texas and composes one of the dominant physiographic elements of the State, the Edwards Plateau.