Limestone samples collected from established stratigraphic horizons in outcropping Pennsylvanian rocks of Iowa, Missouri, and Kansas have been subjected to thermoluminescence study to evaluate the use of thermoluminescence in correlation.

Although each limestone selected for study is a unit whose lateral continuity has been reasonably well demonstrated by other stratigraphic methods, there is wide variation among the limestones in the lateral persistence of specific thermoluminescence properties. Some show fairly persistent thermoluminescence patterns over a township-to-county area, whereas other limestones show wide variation within a square mile.

Because lithologic factors, chemical composition, radioactivity, recrystallization, cyclical sedimentation, and sampling interval are capable of exerting a control upon thermoluminescence itself or influencing the interpretation of the results obtained, correlation by thermoluminescence is subject to severe limitations.

Thermoluminescence curves from cyclical limestones of the Kansas City and Shawnee groups show cyclical repetitions. A relationship between glow-curve shape and lithologic character is suggested for some limestones in the cyclical sequences, but the factors controlling thermoluminescence are complex and need further study. In the limestones studied, radioactivity is either of secondary importance or its effects are masked by other factors.