Single plagioclase crystals separated from lavas can contain minute magnetic inclusions that faithfully record the geomagnetic field, while the silicate host limits natural and experimentally induced alteration. Here we use paleointensity analyses of plagioclase crystals to examine three characteristic geodynamo regimes spanning the last 200 Myr: an interval of moderate reversal frequency during the Paleogene, the nonreversing field of the Cretaceous Normal Polarity Superchron, and a period of very high reversal occurrence during the Late Jurassic. An inverse relationship between reversal rate and intensity is supported. Furthermore, the strength of the time-averaged reversing field is more variable than that of the nonreversing field. These observations are consistent with an active lower mantle, shaping core-mantle boundary heat flux and efficiency of the geodynamo on timescales of tens of millions of years.