A new δ18O Phanerozoic database, based on 24,000 low-Mg calcitic fossil shells, yields a prominent 32 Ma oscillation with a secondary 175 Ma frequency modulation. The periodicities and phases of these oscillations are consistent with parameters postulated for the vertical motion of the solar system across the galactic plane, modulated by the radial epicyclic motion.
The Milky Way is a barred spiral galaxy. As a consequence, the solar system revolves around the galaxy and carries out a small oscillation in the direction perpendicular to the dense galactic disk, with a period much shorter than its orbital period
http://www.nature.com/articles/srep06150
