An analysis of seafloor spreading lineations in the southern Gulf of California demonstrates that divergence of the Baja peninsula from North America since 3.6 Ma has been significantly slower than Pacific-North America (PA-NA) motion estimated solely from closures of global plate circuits. This discrepancy remains unchanged or increases with modifications to the plate circuits and kinematic data used to predict PA-NA motion, suggesting that it arises from the probably-incorrect assumption that Baja California has been rigidly coupled to the Pacific plate since 3.6 Ma. A ~15% increase in seafloor spreading rates in the southern Gulf after ~1 Ma could have been caused by a transfer of motion along faults west of Baja California to the modern-day plate boundary, or alternatively could indicate a recent speedup in PA-NA motion. Both interpretations imply that PA-NA motion is now 4¿2 mm yr-1 (2&sgr;) faster than predicted by the 3.16-Myr-average NUVEL-1A model. ¿ American Geophysical Union 1995