A multidisciplinary study of the Spiro Sandstone shows that in Pittsburg and Latimer counties, Oklahoma, along the Choctaw fault trend, the thrusted Spiro is predominantly a barrier island deposit consisting of reservoir-quality progradational and aggradational sandstones; however, to the east from Le Flore County, Oklahoma, through Yell County, Arkansas, along the structural trend, the Spiro is composed predominantly of tight, nonproductive, retrogradational sandstones. Petrographic observations of the progradational Spiro show that sands in the west are medium to fine grained, and in the east they are very fine grained. Chlorite coatings that inhibit quartz cementation are present only in the west. Vitrinite reflectance data indicate that the Spiro in the west is within the gas window (~1.5% R₀), but in the east it is overmature (>2.5% R₀). The term "overmature" applies to reservoirs that have insufficient porosity for commercial production due to destructive diagenesis caused by thermal stress. The simultaneous multidisciplinary approach is economically significant because exploration analysis time for this study was decreased, and decisions were made with more reliability.