This project, whose ultimate goal is to develop a high-resolution temporal framework for the Leonardian (Lower Permian) using a synthesis of conodont and fusulinid biostratigraphy, strontium isotope chemostratigraphy, and sequence stratigraphy, was completed in 2002. The sequence stratigraphy of the Leonardian was worked out through integrated studies of outcrops in the Sierra Diablo Mountains of West Texas and subsurface data from the Permian Basin. Primary focus during the past year was the collection of additional samples from outcrops and subsurface cores within this sequence-stratigraphic framework for processing and recovery of conodonts. Outcrop samples were collected from platform margin sections where the likelihood of recovery of conodonts appears greatest. Additional samples were collected from a subsurface core that spans a large part of the Leonardian section. Conodonts recovered from these samples and from whole rock samples likely to preserve original seawater chemistry were analyzed for 87Sr/86Sr to provide a secular record of seawater variations in 87Sr/86Sr during the Leonardian. Diagenetic mineral phases (anhydrite and dolomite) were also sampled from subsurface cores and analyzed for 87Sr/86Sr to investigate the history and timing of carbonate diagenesis. The 87Sr/86Sr data provided from conodonts and nondiagenetic phases will serve as a primary reference standard for comparison, correlation, and dating of equivalent successions worldwide. Data from diagenetic phases will provide important insights into the process of reflux diagenesis. The project was funded by the Texas Higher Education Coordinating Board as part of the Advanced Research Program.