Measurement of protactinium-231 (Pa-231) in carbonates by thermal ionization mass spectroscopy yields Pa-231 ages that are more than 10 times more precise than those determined by decay counting. Carbonates between 10 and 250,000 years old can now be dated with Pa-231 methods. Barbados corals that have identical Pa-231 and thorium-230 (Th-230) ages indicate that the timing of sea level change over parts of the last glacial cycle is consistent with the predictions of the Astronomical Theory. Two Devils Hole calcite subsamples record identical Pa-231 and Th-230 ages, suggesting that the chronology of this climate record is accurate.