Counterproofs changes in strontium isotopic ratios (87Sr/86Sr) in oceanic waters are not detectable because they occur very slowly. Strontium is incorporated into the calcareous structure of living organisms that eventually precipitate with other sediments. The 87Sr/86Sr of oceanic waters at different geologic times can be estimated by measuring this ratio in the calcareous shells of living organisms incorporated with sedimentary rocks. By studying changes in isotopic ratios of 87Sr/86Sr, comparable age correlation, similar to that from other conventional techniques can be established. By applying this study method, geologists, paleontologists and oceanographists have been able to find answers for many ambiguities. In this study, the strontium isotopic ratios for 201 cutting samples from Well Sulabdar#3 located in the southern part of North Dezful (from an interval with the age of Paleogene to lower Jurassic) were measured and a 87Sr/86Sr profile was established and compared with the world’s profile. Results show that there is a good correlation between the87Sr/86Sr data obtained for Paleogene-Jurassic sediments with the corresponding data reported for the evolutionary curve of the Phanerozoic seas.