The Amerada Petroleum Corporation No. 1 Moore oil test in Yalobusha County, Mississippi, drilled through sediments of Cretaceous age into granite at 3380 ft. The total depth is 3890 ft. The granite is medium grained and contains microcline perthite, plagioclase, and quartz in roughly equal amounts. Rb-Sr and K-Ar isotopic age determinations of 190 m. y. on biotite and feldspar correspond approximately to the Triassic-Jurassic boundary.