The sand clay formation here represents the first prominent Coastal Plain deposits laid upon an ancient floor of granites and gneisses. Southward, this formation, the Tuscaloosa Upper Cretaceous, becomes more and more deeply buried and contains marine beds. These rocks are more than 60,000,000 years old. Still older Lower Cretaceous rocks underlie them down the dip. Oil fields of Alabama and Mississippi are from marine beds of this formation, which occur also in Georgia to the south, indicating oil in Georgia too.