During Ocean Drilling Program Leg 200, approximately 45 Ma igneous basement, was cored in the northeastern Pacific at Site 1224. The basement surface was inferred to be 28 meters below seafloor (mbsf). Basement lithology down to 170 mbsf is divided into three major units: Unit 1 = massive flow, Unit 2 = pillow breccia, and Unit 3 = intermixed pillows and thin flows. The bulk compositions of Site 1224 rocks have high abundances of the high-field strength elements (HFSE) Y, Zr, and Nb relative to normal and even enriched mid-ocean-ridge basalts. Chemical stratigraphic differences among the three units at this site are clear. Unit 3 rocks have the highest FeO/MgO ratio and HFSE concentration, and Unit 2 lavas have the lowest. Unit 2 lavas also have the highest Y/Zr ratios. Unit 1 is separated into lower and upper flow units based on differences in HFSE content. Clearly, there were significant differences in the petrogenetic processes that created these units. Compositional and lithologic differences among the basement units correlate with differences in physical properties among the units described by the Leg 200 Shipboard Scientific Party. Physical properties are therefore associated with petrological features.