A new technique is described, in which both natural alpha emitters and fissionable nuclides are measured in geologic samples. If the sample is in secular equilibrium the alpha measurements will define the total U and Th contents, while the fission measurements will give the U alone. Probably of more interest will be those cases not in secular equilibrium, where comparison of the alpha and fission measurements will define excess or deficient radioactivities. Particular examples are coral growth and deep sea sedimentation. Some data on the latter are presented.